Characterization of patients with dermatomyositis in a university hospital in Colombia

Introduction: Dermatomyositis is an idiopathic inflammatory myopathy characterized by the presence of skin lesions; it is considered a heterogeneous disease, due to its clinical presentation, course, and prognosis. In Colombia there are few records that describe the clinical characteristics of these patients. Methods: Cross-sectional study. Medical records of patients who consulted a university hospital in Colombia between January 2004 and December 2019 were reviewed. The records were obtained using databases from the dermatology, rheumatology, dermatopathology, and electrophysiology units, and CIE10 diagnostic codes. Results: Seventy patients with a dermatomyositis diagnosis were found, 63 (90%) fulfilled the Bohan and Peter diagnostic criteria and 7 (10%) had amyopathic dermatomyositis, with an average age of 43 years (SD ± 15.3). Forty-eight were women (68.5%). The most frequent clinical signs were Gottron's papules 80%, periorbital violaceous (heliotrope) erythema with edema 78.5% (n = 55) and poikiloderma 75.7% (n = 53). The most frequently found systemic manifestations were dysphagia (21.4%, n = 15), interstitial lung disease (11.4%, n = 8), and pulmonary hypertension (8.5%, n = 6). Cancer was documented in 8.5% (n = 6) of patients. Conclusion: We showed clinical information of patients with dermatomyositis in a referral hospital in Colombia. The data obtained is consistent with information from other case series worldwide.

Introducción: La dermatomiositis es una miopatía inflamatoria idiopática que se caracteriza por presentar lesiones en la piel; por su presentación clínica, su curso y su pronóstico, se la considera una enfermedad heterogénea. En Colombia existen pocos registros que describan las características clínicas de los pacientes afectados por esta enfermedad. Métodos: Estudio descriptivo de corte transversal, se revisaron las historias clínicas de pacientes que consultaron a un hospital universitario en Colombia entre enero del 2004 y diciembre del 2019. Los registros se obtuvieron utilizando bases de datos de las unidades de dermatología, reumatología, dermatopatología, electrofisiología y códigos diagnósticos CIE10 asociados con dermatomiositis. Resultados: Se obtuvieron 70 pacientes con diagnóstico de dermatomiositis, 63 (90%) de los cuales cumplían criterios de clasificación de Bohan y Peter, en tanto que 7 (10%) presentaban dermatomiositis amiopática. El promedio de edad fue de 43 arios (DS ± 15,3); 48 fueron mujeres (68,5%); los signos clínicos más frecuentes fueron: pápulas de Gottron (80%, n = 56), eritema heliotropo (78,5%, n = 55) y poiquilodermia (75,7%, n = 53). Las manifestaciones sistêmicas más comúnmente encontradas fueron: disfagia (21,4%, n = 15), enfermedad pulmonar intersticial (11,4%, n = 8) e hipertensión pulmonar (8,5%, n = 6). Se documentó cáncer en el 8,5% (n = 6) de los pacientes. Conclusión: Se presenta información clínica de pacientes con dermatomiositis en un centro hospitalario de referencia en Colombia; los datos obtenidos concuerdan con la información de otros estudios de series de casos a escala mundial.

Wooden breast and white striping: comparative occurrence in three poultry companies

ABSTRACT: To increase the amount of meat produced, researchers have promoted intensive genetic selection for growth rate and muscling and have improved nutrition and management conditions. However, there has been an increase in the number of reports of breast muscle myopathies observed in poultry processing plants, including white striping (WS) and wooden breast (WB). This study aimed to evaluate and to compare the occurrence of WS and WB myopathies in three poultry processing plants and to perform an anatomopathological characterization, including macroscopic and microscopic analyses. A total of 408,334 carcasses were condemned or downgraded due to the presence of WB or WS, which represents 0.73% of the total number of slaughtered animals during the evaluated period. WB was more frequent than WS, but the occurrence of each myopathy varied significantly according to each establishment. WB was more frequent in the establishment which includes only male flocks, an average age of 45 days, and an average live weight of 2775g (B). WS was more frequent in establishment with male, female and mixed flocks, average ages ranging from 41 to 44 days, and average live weight 1731g-2830g (A). It is probably related with specific condition of each poultry company, including genetics, age, nutrition and management conditions. Macroscopically, WB and WS lesions are characterized by hypertrophy and stiffness of the pectoralis major muscle. Under microscopy, the myopathies showed similarities regarding the detected histological abnormalities, characterized by a process of myodegeneration, although the connective tissue infiltrate was more severe in the breasts with WB than in those with WS myopathy. The results found in this study demonstrate that the rates of condemnation for these myopathies are high, vary significantly among the analyzed companies and may cause major economic losses for the productive sector in the region.

RESUMO: Para melhorar a quantidade de carne produzida, os pesquisadores têm promovido ao longo dos anos uma seleção genética intensiva para a taxa de crescimento e desenvolvimento de músculos, além de melhorias nas condições nutricionais, sanitárias e de manejo. No entanto, houve um aumento no número de relatos de miopatias dos músculos do peito observados em abatedouros-frigoríficos de aves, incluindo white striping (WS) e wooden breast (WB). O objetivo deste estudo foi avaliar a ocorrência de WB e WS em três abatedouros-frigoríficos de aves e realizar uma caracterização anatomopatológica, incluindo análises macroscópicas e microscópicas. Um total de 408.334 carcaças foi condenado (total ou parcialmente) devido à presença WB ou WS, o que representou 0,73% do número total de animais abatidos durante o período avaliado. Apesar de a ocorrência de WB ter sido maior do que a de WS, a frequência de cada uma variou significativamente de acordo com o estabelecimento. WB foi mais frequente no estabelecimento que incluía apenas lotes de machos, com média de 45 dias de idade e peso médio ao abate de 2775g (B). WS foi mais frequente no estabelecimento com lotes de machos, fêmeas e mistos, com idade entre 41 e 44 dias e peso médio ao abate entre 1731g-2830g (A). Isto pode ser justificado por condições específicas de cada empresa, incluindo genética, idade das aves, nutrição e condições de manejo. Macroscopicamente, as lesões de WB e de WS foram caracterizadas principalmente por hipertrofia e rigidez do músculo pectoralis major. À microscopia, ambas as miopatias mostraram semelhanças em relação às anormalidades histológicas detectadas, caracterizadas principalmente por um processo de miodegeneração. Nos músculos apresentando WB, o infiltrado de tecido conjuntivo foi mais intenso quando comparado àqueles com WS. Os resultados encontrados neste trabalho demonstram que os índices de condenação por essas miopatias são altos, variam significativamente entre as empresas analisadas e podem causar grandes perdas econômicas para o setor produtivo da região.

Wooden breast and white striping: comparative occurrence in three poultry companies / Wooden breast e white striping: ocorrência em três empresas avícolas

To increase the amount of meat produced, researchers have promoted intensive genetic selection for growth rate and muscling and have improved nutrition and management conditions. However, there has been an increase in the number of reports of breast muscle myopathies observed in poultry processing plants, including white striping (WS) and wooden breast (WB). This study aimed to evaluate and to compare the occurrence of WS and WB myopathies in three poultry processing plants and to perform an anatomopathological characterization, including macroscopic and microscopic analyses. A total of 408,334 carcasses were condemned or downgraded due to the presence of WB or WS, which represents 0.73% of the total number of slaughtered animals during the evaluated period. WB was more frequent than WS, but the occurrence of each myopathy varied significantly according to each establishment. WB was more frequent in the establishment which includes only male flocks, an average age of 45 days, and an average live weight of 2775g (B). WS was more frequent in establishment with male, female and mixed flocks, average ages ranging from 41 to 44 days, and average live weight 1731g-2830g (A). It is probably related with specific condition of each poultry company, including genetics, age, nutrition and management conditions. Macroscopically, WB and WS lesions are characterized by hypertrophy and stiffness of the pectoralis major muscle. Under microscopy, the myopathies showed similarities regarding the detected histological abnormalities, characterized by a process of myodegeneration, although the connective tissue infiltrate was more severe in the breasts with WB than in those with WS myopathy. The results found in this study demonstrate that the rates of condemnation for these myopathies are high, vary significantly among the analyzed companies and may cause major economic losses for the productive sector in the region.(AU)

Para melhorar a quantidade de carne produzida, os pesquisadores têm promovido ao longo dos anos uma seleção genética intensiva para a taxa de crescimento e desenvolvimento de músculos, além de melhorias nas condições nutricionais, sanitárias e de manejo. No entanto, houve um aumento no número de relatos de miopatias dos músculos do peito observados em abatedouros-frigoríficos de aves, incluindo white striping (WS) e wooden breast (WB). O objetivo deste estudo foi avaliar a ocorrência de WB e WS em três abatedouros-frigoríficos de aves e realizar uma caracterização anatomopatológica, incluindo análises macroscópicas e microscópicas. Um total de 408.334 carcaças foi condenado (total ou parcialmente) devido à presença WB ou WS, o que representou 0,73% do número total de animais abatidos durante o período avaliado. Apesar de a ocorrência de WB ter sido maior do que a de WS, a frequência de cada uma variou significativamente de acordo com o estabelecimento. WB foi mais frequente no estabelecimento que incluía apenas lotes de machos, com média de 45 dias de idade e peso médio ao abate de 2775g (B). WS foi mais frequente no estabelecimento com lotes de machos, fêmeas e mistos, com idade entre 41 e 44 dias e peso médio ao abate entre 1731g-2830g (A). Isto pode ser justificado por condições específicas de cada empresa, incluindo genética, idade das aves, nutrição e condições de manejo. Macroscopicamente, as lesões de WB e de WS foram caracterizadas principalmente por hipertrofia e rigidez do músculo pectoralis major. À microscopia, ambas as miopatias mostraram semelhanças em relação às anormalidades histológicas detectadas, caracterizadas principalmente por um processo de miodegeneração. Nos músculos apresentando WB, o infiltrado de tecido conjuntivo foi mais intenso quando comparado àqueles com WS. Os resultados encontrados neste trabalho demonstram que os índices de condenação por essas miopatias são altos, variam significativamente entre as empresas analisadas e podem causar grandes perdas econômicas para o setor produtivo da região.(AU)

Miopatia mitocondrial e deficiência auditiva neurossensorial: estudo de caso / Mitochondrial myopathy and sensorineural hearing loss: case study

Resumo A miopatia mitocondrial é causada pela ausência e/ou insuficiência de uma enzina quaternária, L-carnitina, responsável por transportar ácidos graxos livres para a parte interna da mitocôndria. A função da mitocôndria é produzir energia, contribuindo para o bom funcionamento das células. A Lipidose Muscular é uma doença que provoca anomalias em enzimas que metabolizam gordura e por consequência causa acúmulo de toxinas de subprodutos com gordura nos tecidos. O objetivo deste trabalho é apresentar o estudo de caso da paciente B.D., 37 anos, diagnosticada com Lipidose Muscular aos seis anos, com deficiência de L-Carnitina e relatar o acompanhamento fonoaudiológico realizado em um serviço de saúde auditiva. A abertura de prontuário da paciente foi realizada em 05/03/1989. Foi prescrito pelo neurologista o uso contínuo de 2g/dia de L-carnitina. A mãe relatou que B.D. apresentava dificuldades em ouvir, pois era muito desatenta, o que foi mais evidente quando começou a frequentar a escola. Em 1988, a paciente foi diagnosticada com perda auditiva neurossensorial de grau moderado bilateral e começou a fazer uso de aparelhos de amplificação sonora individual retroauriculares em 1989. O desempenho escolar e comunicação melhoraram. Em 1998, passou a utilizar aparelhos tipo micro canal, o que a favoreceu esteticamente, promoveu melhora da localização sonora e maior ganho em altas frequências. Os limiares de audibilidade apresentaram uma leve piora e a paciente atualmente é pós-graduada e trabalha em uma grande instituição financeira. Conclui-se que o diagnostico neurológico e a intervenção fonoaudiológica precoces possibilitaram o adequado desenvolvimento de linguagem da paciente.

Abstract Mitochondrial myopathy is caused by the absence and/or insufficiency of L-carnitine, a quaternary enzyme responsible for transporting free fatty acids into the mitochondria. The primary function of the mitochondria is to produce energy, contributing to proper cell functioning. Muscular lipidosis causes abnormalities in enzymes that metabolize fat, resulting in the accumulation of harmful amounts of fats in tissues. The aim of this study was to present the case study of patient B.D., a 37-year-old woman diagnosed with muscular lipidosis with L-carnitine deficiency at 6 years old, and describe the speech-language follow-up performed at a hearing care clinic. The first entry in the patient's medical chart was on 03/05/1989, with continuous use of 2g/day of L-carnitine prescribed by a neurologist. The mother reported that B.D. had difficulty hearing and was inattentive, which became more evident when she started school. In 1988 the patient was diagnosed with moderate bilateral sensorineural hearing loss and began using behind-the-ear (BTE) hearing aids in 1989, after which her academic performance and communication improved. In 1998 she switched to Completely in Canal (CIC) hearing aids, which are more discreet, provided better sound localization and greater high frequency gain, although her hearing thresholds worsened slightly. She completed her graduate studies and currently works at a large financial institution. It was concluded that early neurological diagnosis and speech-language intervention enabled adequate language development in the patient.

Inicio de dermatomiositis juvenil en un escolar de 7 años de edad / Debut of juvenile dermatomyositis in a 7-year-old schoolboy

La dermatomiositis es una enfermedad que afecta con mayor frecuencia a pacientes mayores de 60 años y preferiblemente del sexo femenino. Sin embargo, en algunas ocasiones aparece en la edad infantil. Se exponen los elementos medulares que permiten el diagnóstico de esta enfermedad. Se presenta el caso de una escolar de 7 años de edad que acude al servicio de emergencia con manifestaciones clínicas sugerentes de una dermatomiositis juvenil. Las manifestaciones clínicas y los resultados de los exámenes complementarios permitieron llegar al diagnóstico definitivo de la enfermedad. Fue necesario hacer el diagnóstico diferencial con otras afecciones que cursan con síntomas similares. La paciente comenzó a mostrar una evolución favorable, lo que motivó el alta hospitalaria con tratamiento para el hogar y seguimiento por consulta externa con la especialidad de Reumatología. Conclusiones: A pesar de presentar un patrón epidemiológico predominante en adultos mayores, la dermatomiositis puede aparecer en edades más tempranas. Aunque las manifestaciones clínicas orientan hacia su diagnóstico, este se confirma con la ayuda de determinados exámenes complementarios(AU)

Dermatomyositis is a disease that occurs more frequently in patients older than 60 years and preferably female; however, sometimes it occurs in children. To publicize the core elements that allow the diagnosis of this disease. The case of a 7-year-old schoolgirl who comes to the emergency service with clinical manifestations suggesting a juvenile dermatomyositis is presented. The clinical manifestations and the results of the complementary examinations allowed to reach the definitive diagnosis of the disease, it was necessary to make the differential diagnosis with other conditions that present with similar symptomatology. Conclusions: despite presenting a predominant epidemiological pattern in older adults, dermatomyositis may occur at earlier ages; although the clinical manifestations are oriented towards its diagnosis, it is confirmed with the help of certain complementary tests(AU)

Avances en el empleo del ultrasonido muscular en miopatías inflamatorias / Advances in the use of muscle ultrasound in inflammatory myopathies

Aunque los métodos de imágenes aún no se han introducido en los criterios de clasificación de la miositis, el uso de imágenes musculares en la evaluación de las miopatías inflamatorias idiopáticas (MII) ha crecido a lo largo de los años. Las diferentes técnicas de imagen han demostrado ser útiles, pero la RM sigue siendo el estándar de oro para la imagen muscular. Sin embargo, el alto costo y las contraindicaciones en algunos pacientes, hacen considerar otros métodos como el ultrasonido muscular. Esta revisión tiene el objetivo de ofrecer una visión general de las diferentes técnicas de ultrasonido que se han estudiado y proporcionar información a los reumatólogos sobre el papel actual del ultrasonido para diagnosticar las MII. Existen diversos factores que pueden influir en la medición de los parámetros musculares: estandarizar la configuración de la máquina, el plano de visión y la posición del paciente, ya que pueden afectar la medición de la intensidad del eco y el grosor muscular. En el caso de las miopatías inflamatorias influyen otros factores en los resultados de la imagen: sexo, edad, escala de grises de la imagen, cambios en la calidad muscular, intensidad del eco, grosor, tamaño y ecogenicidad muscular. La ecografía muscular es una herramienta próxima en la evaluación de los trastornos neuromusculares y las miopatías inflamatorias. Es fácilmente aplicable en diversos entornos clínicos, no tiene contraindicaciones y proporciona una alternativa rentable a otras modalidades de imágenes como la resonancia magnética(AU)

Although imaging methods have not yet been introduced into the myositis classification criteria, the use of muscle imaging in the evaluation of IIMs has grown over the years. Different imaging techniques have proven helpful, but MRI remains the gold standard for muscle imaging. In this review, the objective is to provide an overview of the different ultrasound techniques that have been studied and to provide information to rheumatologists about the current role of ultrasound in the field of IIM. Development: There are multiple factors that can influence the measurement of muscle parameters that must be considered. First, it is important to standardize the machine configuration, the plane of vision and the position of the patient, as these can affect the measurement of echo intensity and muscle thickness. Conventionally, a linear ultrasound probe is used with sufficient frequency (at least 6-12 MHz) to obtain images of the peripheral skeletal muscle. Magnetic resonance imaging remains the gold standard for muscle imaging. However, the role as a diagnostic tool in the field of IIMs has grown over the years, and the promising results of new advanced imaging techniques suggest that it has not yet reached its full potential(AU)

Métodos de diagnóstico en el estudio de las Miopatías Inflamatorias Autoinmunes: Datos del Registro Argentino de Miopatías Inflamatorias de la Sociedad Argentina de Reumatología / Diagnostic methods in the study of Inflammatory Myopathies. Data from the Argentine Register: Argentine Rheumatology Society

Las Miopatías Inflamatorias Autoinmunes (MI) comprenden un grupo de enfermedades heterogéneas con presentación y características clínicas variables. Se distinguen subtipos clínicos como Polimiositis (PM), Dermatomiositis (DM), Miositis por cuerpos de Inclusión (MCI), Miopatía Necrotizante Inmunomediada (MNIM), Miositis de los Síndromes de Superposición, formas juveniles de MI (DMJ), Síndrome Antisintetasa (SAS) y Miopatía Asociada a Cáncer (MAC). La presencia de anticuerpos séricos y el infiltrado inflamatorio en la biopsia de músculo sugiere que se trata de una condición autoinmune. Realizar el diagnóstico de las MI suele ser un desafío y las herramientas diagnósticas no siempre están disponibles en la práctica diaria. Se obtuvo información sobre la disponibilidad de estos métodos del Registro Argentino de Miopatías Inflamatorias. El estudio de enzimas musculares, Anticuerpos Antinucleares (ANA), anticuerpo anti-Jo-1 y la tomografía computada de tórax, estuvieron disponibles para la mayoría de los pacientes mientras que la Resonancia Magnética de musculo (RM), el estudio de difusión de monóxido de carbono (DLco) y la biopsia muscular se realizaron en menos del 50% de los casos. La determinación de otros anticuerpos específicos de miositis, de importancia en el diagnóstico y pronóstico de la enfermedad se realizó, en mayor parte, a través de un subsidio de la SAR.

The Idiopathic Inflammatory Myopathies (IIM) comprise a heterogeneous group of acquired muscle diseases classified as polymyositis (PM), dermatomyositis (DM), Inclusion Body Myositis (IBM), Immuno Mediated Necrotizing Myopathies (IMNM), Overlap Myositis (OM), juvenile myositis, Antisynthethase Syndrome (ASS) and cancer related myositis (CAM). The presence of myositis specific antibodies in the serum and autoantibodies against target antigens and inflammatory infiltrates in muscle tissue suggests the autoimmune condition of the disease. The diagnosis of inflammatory myopathies is often a challenge and the disposal of diagnostic tools are not always available in daily practice. Information on the accessibility of these methods was obtained from the Argentine Register of Myopathies. The study of muscle enzymes, ANA, anti-Jo-1 antibodies and chest tomography were easy to get to most patients while muscle MRI, lung diffusion capacity for carbon monoxide (DLco) and muscle biopsy were performed in less than 50% of cases. Other myositis specific antibodies, necessary for disease diagnosis and prognosis, were mostly done through a subsidy from the Argentine Rheumatology Society.

Métodos de diagnóstico en el estudio de las Miopatías Inflamatorias Autoinmunes: Datos del Registro Argentino de Miopatías Inflamatorias de la Sociedad Argentina de Reumatología / Diagnostic methods in the study of myopathies Inflammatory Autoimmune: Data from the Argentine Registry of Inflammatory Myopathies of the Argentine Society of Rheumatology

Las Miopatías Inflamatorias Autoinmunes (MI) comprenden un grupo de enfermedades heterogéneas con presentación y características clínicas variables. Se distinguen subtipos clínicos como Polimiositis (PM), Dermatomiositis (DM), Miositis por cuerpos de Inclusión (MCI), Miopatía Necrotizante Inmunomediada (MNIM), Miositis de los Síndromes de Superposición, formas juveniles de MI (DMJ), Síndrome Antisintetasa (SAS) y Miopatía Asociada a Cáncer (MAC).La presencia de anticuerpos séricos y el infiltrado inflamatorio en la biopsia de músculo sugiere que se trata de una condición autoinmune. Realizar el diagnóstico de las MI suele ser un desafío y las herramientas diagnósticas no siempre están disponibles en la práctica diaria. Se obtuvo información sobre la disponibilidad de estos métodos del Registro Argentino de Miopatías Inflamatorias. El estudio de enzimas musculares, Anticuerpos Antinucleares (ANA), anticuerpo anti-Jo-1 y la tomografía computada de tórax, estuvieron disponibles para la mayoría de los pacientes mientras que la Resonancia Magnética de musculo (RM), el estudio de difusión de monóxido de carbono (DLco) y la biopsia muscular se realizaron en menos del 50% de los casos. La determinación de otros anticuerpos específicos de miositis, de importancia en el diagnóstico y pronóstico de la enfermedad se realizó, en mayor parte, a través de un subsidio de la SAR.

The Idiopathic Inflammatory Myopathies (IIM) comprise a heterogeneous group of acquired muscle diseases classified as polymyositis (PM), dermatomyositis (DM), Inclusion Body Myositis(IBM), ImmunoMediated Necrotizing Myopathies, (IMNM), Overlap Myositis(OM), juvenile myositis, Antisynthethase Syndrome (ASS) and cancer related myositis(CAM).The presence of myositis specific antibodies in the serum and autoantibodies against target antigens and inflammatory infiltrates in muscle tissue suggests the autoimmune condition of the disease. The diagnosis of inflammatory myopathies is often a challenge and the disposal of diagnostic tools are not always available in daily practice. Information on the accessibility of these methods was obtained from the Argentine Register of Myopathies. The study of muscle enzymes, ANA, anti-Jo-1 antibodies and chest tomography were easy to get to most patients while muscle MRI, lung diffusion capacity for carbon monoxide (DLco%) and muscle biopsy were performed in less than 50% of cases. Other myositis specific antibodies, necessary for disease diagnosis and prognosis, were mostly done through a subsidy from the Argentine Rheumatology Society.

Neumopatía crónica secundaria al trastorno de la deglución en un paciente con miopatía mitocondrial / Chronic pneumopathy secondary to swallowing disorder in a patient with mitochondrial myopathy

RESUMEN Introducción: la enfermedad pulmonar crónica secundaria a la disfagia es una complicación frecuente en los pacientes con enfermedades neuromusculares. Las miopatías mitocondriales son un conjunto de enfermedades que pueden conducir a daño pulmonar progresivo, secundario al síndrome aspirativo crónico. Caso clínico: niño de 7 años con signos clínicos y radiológicos de enfermedad pulmonar crónica; además, con desnutrición crónica, debilidad muscular, disfonía y oculoparesia externa crónica multiplanar. Su padre tuvo síntomas similares desde la infancia y requirió alimentación con dieta espesa por trastorno de la deglución. Se confirma en el paciente la presencia de disfagia como la causa de la neumopatía crónica y se sospecha miopatía congénita hereditaria. En consecuencia, se realiza el diagnóstico de enfermedad mitocondrial con oculoparesia externa crónica, mediante la secuenciación del gen polimerasa gamma del ADN mitocondrial (POLG). Conclusiones: en los pacientes con neumopatía crónica se deben considerar las enfermedades neuromusculares en el diagnóstico diferencial. La miopatía mitocondrial con oculoparesia externa crónica progresiva, se asocia con trastorno de la deglución hasta en un 50 % de los casos. El diagnóstico temprano es importante para retardar el deterioro de la función pulmonar.

SUMMARY Introduction: Chronic lung disease secondary to dysphagia is a frequent complication in patients with neuromuscular diseases. Mitochondrial myopathies could lead to progressive lung damage due to chronic aspiration syndrome. Clinical case: Seven-year-old male with clinical and radiological signs of chronic lung disease, as well as low weight, weakness, dysphonia and multiplanar external oculoparesis. His father had similar symptoms during infancy and needed thickened liquid diet due to swallowing disorder. Dysphagia was confirmed as the cause of chronic lung disease and, therefore, hereditary congenital myopathy was suspected. Mitochondrial disease with chronic external oculoparesis was confirmed by molecular sequencing of the mitochondrial DNA gamma polymerase gene (POLG). Conclusion: Neuromuscular disorders may cause chronic lung disease. Mitochondrial myopathy with progressive chronic external oculoparesis is associated with swallowing disorder in 50 % of the cases. Early diagnosis is important to slow decline in lung function.

Autoanticuerpos en miopatías inflamatorias idiopáticas: enfoque en la práctica clínica / Autoantibodies in idiopathic inflammatory myopathies: focus on clinical practice

Las miopatías inflamatorias idiopáticas (MII) conforman un grupo diverso de en-fermedades caracterizadas por lesiones musculares inmunomediadas, que pue-den estar acompañadas de manifestaciones extramusculares.La identificación de autoanticuerpos específicos de miositis (AEM) y asociados a miositis (AAM) se ha convertido en una herramienta relevante en el diagnóstico, clasificación y pronóstico en este grupo de enfermedades.Adquieren relevancia en el diagnóstico y determinación de pronóstico de la Enfer-medad Pulmonar Intersticial (EPI), en el diagnóstico diferencial entre subgrupos de MII, especialmente en entidades de comportamiento atípico como la Miopatía Necrotizante Inmuno Mediada (MNIM) y la Miositis por Cuerpos de Inclusión, y permiten el enfoque y seguimiento estricto en pacientes con autoanticuerpos asociados a cáncer. En el último tiempo se ha planteado su utilidad tanto en la determinación de actividad de la enfermedad como en predecir la respuesta al tratamiento inmu-nosupresor.

Idiopathic inflammatory myopathies (IIM) comprise a heterogenous group of ill-nesses characterized by immune mediated muscular injuries that may be accom-panied by extra-muscular manifestations.The identification of myositis-specific autoantibodies MSAs and myositis-associ-ated autoantibodies (MAA) has become a relevant tool in the diagnose, classifica-tion, and prognosis in this group of illnesses.They become relevant in the diagnose and determination of a prognosis for Inter-stitial Lung Disease (ILD), in the differentiated diagnose among sub-groups of MII, especially in entities of an atypical behavior, such as Immune Mediated Necrotiz-ing Myopathy (IMNM) and Inclusion Body Myositis, and they enable a strict focus and follow-up on patients with cancer-associated autoantibodies. Lately, its usefulness has been stated both to determine disease activity and to forecast the response to the immunosuppressive treatment.

Quantitation of muscle pathology abnormalities in 18 patients with mitochondrial disorders / Quantificação das anormalidades patológicas musculares em 18 pacientes com desordens mitocondriais

ABSTRACT INTRODUCTION: Mitochondrial disorders can lead to the accumulation of mitochondria in muscle fibers, as indicated by ragged red (RRF) or ragged blue fibers when stained with modified Gomori trichrome or succinate dehydrogenase (SDH+), respectively, and, absence of activity of cytochrome c oxidase, COX negative fibers (COX-). The combined COX-SDH stain (COMBO+) can reveal even more COX-deficient fibers. OBJECTIVE: To quantify RRFs, SDH+, COX-, and COMBO+ fibers in muscle biopsies with mitochondrial findings. MATERIAL AND METHODS: We retrospectively selected 18 muscle biopsies with mitochondrial abnormalities based on the Walker criteria (percentage of RRFs/COX- fibers, and clinical picture), and/or the Sleigh criteria (percentage of RRFs, SDH+, and COX- fibers). RESULTS: Females represented 83.3%, with a mean age of 38.6 years (5 months-70 years). Patients were diagnosed with chronic progressive external ophthalmoplegia (CPEO, 66.7%), proximal myopathy (22.2%), idiopathic hyperCKemia (11.1%), Kearns-Sayre syndrome (5.6%), mitochondrial encephalomyopathy with ragged red fibers and stroke-like episodes (5.6%), and a dystrophic pattern (5.6%). Some cases of CPEO were combined with proximal myopathy. The quantitative pathologic findings were: RRFs, 3.95% ± 3.17%; SDH+, 7.55% ± 6.1%; COX-, 10.9% ± 7.2%; COMBO+, 14.22% ± 12.79%. We found a slight variation in the diameter of muscle fibers, no necrosis or proliferative connective tissue, few fibers with internal nuclei, and some cases with fiber type grouping. CONCLUSION: Pathologic events, grouped in ascending order of frequency, were RRFs, SDH+ fibers, COX- fibers, and COMBO+ fibers. These data emphasize the importance of the COMBO technique in revealing occult COX deficiency in muscle fibers.

RESUMO INTRODUÇÃO: Desordens mitocondriais são usualmente caracterizadas por: 1. acúmulo de mitocôndria nas fibras musculares que aparecem como fibras vermelhas rasgadas (FVR) ou azuis rasgadas quando coradas, respectivamente, pelo tricrômio modificado de Gomori ou pelo succinato desidrogenase (SDH+); 2. ausência de atividade da citocromo c oxidase (COX), originando fibras COX negativa (COX-). A combinação de colorações COX e SDH pode revelar ainda mais fibras COX deficiente (COMBO+). Objetivos: Quantificar FVR, SDH+, COX- e COMBO+ em biópsias musculares com anormalidades mitocondriais. MATERIAL E MÉTODOS: Foram analisadas retrospectivamente 18 biópsias com anormalidades mitocondriais com base no critério de Walker (percentagem de FVR/ COX- e quadro clínico) e/ou critério de Sleigh (percentagem de FVR, SDH+ e COX-). RESULTADOS: Sexo feminino representou 83, 3% e média de idade 38, 6 anos (5 meses a 70 anos). Oftalmoplegia externa progressiva crônica (OEPC) representou 66, 7%; miopatia proximal, 22, 2%; hiperCKemia idiopática, 11, 1%; síndrome de Kearns-Sayre, 5, 6%; encefalopatia mitocondrial com FVR e episódios semelhantes a acidente vascular cerebral, 5, 6%; e padrão distrófico, 5, 6%. Alguns casos de OEPC estavam associados à miopatia proximal. Achados patológicos quantitativos: FVR, 3, 95% ± 3, 17%; SDH+, 7, 55% ± 6, 1%; COX-, 10, 9% ± 7, 2%; COMBO+, 14, 22% ± 12, 79%. Encontramos leve variação de calibre das fibras musculares sem necrose ou proliferação de tecido conjuntivo, poucas fibras com núcleos internos e alguns casos com agrupamento de fibras. CONCLUSÃO: As anormalidades patológicas nas fibras musculares em ordem ascendente de frequência foram: FVR, SDH+, COX- e COMBO+. Nossos achados enfatizam a importância da técnica COMBO (COX + SDH) para aumento na frequência de fibras musculares COX deficiente ocultas.

Miopatías relacionadas a colágeno VI: cuando sospecharlas, cómo identificarlas: aporte de la resonancia magnética muscular / Collagen VI related myopathies: when to suspect, how to identify: the contribution of muscle magnetic resonance

Resumen: Las miopatías secundarias a mutaciones en el colágeno VI (M-COLVI) son las más frecuentes en el hemisferio norte, afectando población adulta y pediátrica. No existen datos de su prevalencia en Latinoamérica. Se caracterizan por presentar una gran variabilidad clínica, desde fenotipos severos, como la distrofia muscular congénita de Ullrich (DMCU), a intermedios y leves como la Miopatía de Bethlem (MB). Su inicio también es variable y se extiende desde el período de recién nacido hasta la vida adulta. Dada la presencia de hiperlaxitud articular, el diagnóstico diferencial se debe realizar con diversas enfermedades del tejido conectivo. El algoritmo diagnóstico clásico en muchos pacientes ha sido insuficiente para orientar el estudio genético de forma adecuada, y a partir de esto la resonancia magnética muscular ha emergido como una herramienta de gran utilidad para una mejor aproxima ción diagnóstica de ésta y otras patologías musculares. Esta revisión tiene como objetivo examinar las formas de presentación, características clínicas, estudio diagnóstico específico, diagnóstico dife rencial y manejo de una de las patologías musculares herediatarias más frecuentes, con énfasis en el aporte de la resonancia magnética muscular.

Abstract: Myopathies secondary to collagen VI mutations (COLVI-M) are the most frequent in the northern hemisphere, affecting the adult and pediatric population. There are no data on its prevalence in Latin America. They are characterized by a great clinical variability, from severe phenotypes, such as Ullrich congenital muscular dystrophy (UCMD), to intermediate and mild ones such as Bethlem myopathy (BM). Its onset is also variable and extends from the neonatal period to adulthood. Given the presence of joint hypermobility, the differential diagnosis should be made with various connective tissue diseases. The classical diagnostic algorithm in many patients has been insufficient to guide the genetic study in an adequate way, and from this the muscular magnetic resonance imaging has emerged as a very useful tool for a better diagnostic approach of this and other muscular pathologies. This ob jective of this review is to study the forms of presentation, clinical characteristics, specific diagnostic study, differential diagnosis and management of one of the most frequent hereditary muscular patho logies, with emphasis on the contribution of muscle magnetic resonance imaging.

McArdle's disease: an underestimated or underdiagnosed myopathy in rheumatologic practice? Cases series and literature review / Doença de mcardle: uma miopatias subestimada e subdiagnosticada na pratica reumatológica? série clínica e revisão de literatura

OBJECTIVE: McArdle's disease is a metabolic myopathy that manifests with varied clinical conditions and is often confounded with other diagnoses. Herein, the authors report a case series and carry out a literature review. METHODS: A cross-sectional single-center study evaluating 12 patients with McArdle's disease was conducted. RESULTS: Mean age at onset of symptoms was 28.0±17.4 years, while age at disease diagnosis was 39.0±14.8 years. History of intolerance to physical exercises was observed in 10 cases; muscle weakness in 9, second wind phenomenon in only 1 case. The presence of cramps, fatigue and myalgia was observed in 12, 11 and 9 of the cases respectively. Median creatine phosphokinase level was 5951U/L. Most of the patients (83.3%) were initially diagnosed with another condition (polymyositis, inclusion body myositis, fibromyalgia and/or muscular dystrophy), and approximately half had received glucocorticoids and/or immunosuppressants prior to definitive diagnosis. All patients underwent muscular biopsy, which revealed the presence of subsarcolemmal vacuoles characterized by glycogen deposits, and negative histochemical reaction for the myophosphorylase enzyme. CONCLUSION: The present study reinforces the presence of clinical variability among patients and shows that McArdle's disease should be considered one of the differential diagnoses of inflammatory myopathies and other rheumatic diseases.

OBJETIVO: A doença de McArdle é uma miopatia metabólica que se manifesta com condições clínicas variadas e muitas vezes é confundida com outros diagnósticos. Os autores relatam uma série de casos e realizam uma revisão de literatura. MÉTODOS: Estudo transversal de um único centro em que foram avaliados 12 pacientes com doença de McArdle. RESULTADOS: A média de idade no início dos sintomas foi de 28,0±17,4 anos, enquanto a idade no diagnóstico da doença foi de 39,0±14,8 anos. História de intolerância ao exercício físico foi observada em 10 dos casos; fraqueza muscular em 9; fenômeno do "second wind" em apenas 1 caso. A presença de câimbras, fadiga e mialgia foi observada, respectivamente, em 12, 11 e 9 dos casos. O nível mediano de creatinafosfoquinase foi de 5951U/L. Oito pacientes foram inicialmente diagnosticados com outra condição (polimiosite, miosite de corpos de inclusão, fibromialgia e/ou distrofia muscular), e aproximadamente metade havia recebido glicocorticoides e/ou imunossupressores antes do diagnóstico definitivo. Todos os pacientes foram submetidos à biópsia muscular, que revelou a presença de vacúolos subsarcolêmicos caracterizados por depósitos de glicogênio e reação histoquímica negativa para a enzima miofosforilase. CONCLUSÕES: O presente estudo reforça a presença de variabilidade clínica entre pacientes e mostra que a doença de McArdle deve ser considerada um dos diagnósticos diferenciais de miopatias inflamatórias e outras doenças reumáticas.

Analysis of sexual function of patients with dermatomyositis and polymyositis through self-administered questionnaires: a cross-sectional study / Análise da função sexual de pacientes com dermatomiosite e polimiosite através de questionários autoaplicados: um estudo transversal

Abstract Introduction: To date, there are no descriptions in the literature on gynecologic and sexual function evaluation in female patients with dermatomyositis (DM) and polymyositis (PM). Objective: To assess sexual function in female patients with DM/PM. Patients and methods: This is a monocentric, cross-sectional study in which 23 patients (16 DM and 7 PM), with ages between 18 and 40 years, were compared to 23 healthy women of the same age group. Characteristics on sexual function were obtained by applying the questionnaires Female Sexual Quotient (FSQ) and Female Sexual Function Index (FSFI) validated for the Brazilian Portuguese language. Results: The mean age of patients was comparable to controls (32.7 ± 5.3 vs. 31.7 ± 6.7 years), as well as the distribution of ethnicity and socioeconomic class. As for gynecological characteristics, patients and healthy controls did not differ with respect to age at menarche and percentages of dysmenorrhea, menorrhagia, premenstrual syndrome, pain at mid-cycle, mucocervical secretion, and vaginal discharge. The FSQ score, as well as all domains of the FSFI questionnaire (desire, arousal, lubrication, orgasm and satisfaction), were significantly decreased in patients vs. controls, with 60.9% of patients showing some degree of sexual dysfunction. Conclusions: This was the first study to identify sexual dysfunction in patients with DM/PM. Therefore, a multidisciplinary approach is essential for patients with idiopathic inflammatory myopathies, in order to provide prevention and care for their sexual life, providing a better quality of life, both for patients and their partners.

Resumo Introdução: Até o presente momento, não há descrições na literatura da avaliação ginecológica e da função sexual em pacientes do sexo feminino com dermatomiosite (DM) e polimiosite (PM). Objetivos: Avaliar a função sexual em pacientes do sexo feminino com DM/PM. Casuística e métodos: Estudo transversal unicêntrico em que 23 pacientes (16 DM e sete PM), entre 18 e 40 anos, foram comparadas com 23 mulheres saudáveis, com a mesma faixa etária. As características sobre a função sexual foram obtidas por meio da aplicação dos questionários Female Sexual Quotient (FSQ) e Female Sexual Function Index (FSFI) validados para a língua portuguesa do Brasil. Resultados: A média de idade das pacientes foi comparável à dos controles (32,7 ± 5,3 vs. 31,7 ± 6,7 anos), assim como a distribuição de etnia e da classe socioeconômica. Quanto às características ginecológicas, pacientes e controles saudáveis não apresentaram diferenças em relação à idade na menarca e às porcentagens de dismenorreia, menorragia, síndrome pré-menstrual, dor no meio do ciclo, secreção mucocervical e corrimento vaginal. O escore de pontuação do FSQ, assim como todos os domínios do questionário do FSFI (desejo, excitação, lubrificação, orgasmo e satisfação), estavam significantemente diminuídos nas pacientes comparativamente com os controles, 60,9% das pacientes apresentavam algum grau de disfunção sexual. Conclusões: Este foi o primeiro estudo que identificou disfunção sexual nas pacientes com DM/PM. Assim, uma abordagem multidisciplinar é essencial para pacientes com miopatias inflamatórias idiopáticas para fornecer medidas de prevenção e cuidados para sua vida sexual e propiciar uma melhor qualidade de vida das pacientes e de seus parceiros.

Miopatías inflamatorias con evolución recidivante / Relapses in inflammatory myopathies

La mayoría de los estudios de tratamiento de las miopatías inflamatorias son de corte y no permiten establecer su eficacia en largo plazo. En este trabajo, describimos el seguimiento de siete pacientes con miopatías inflamatorias, 5 polimiositis y 2 dermatomiositis. Determinamos su presentación, su seguimiento clínico mediante el examen físico, las enzimas musculares y la respuesta al tratamiento. Esta última la definimos como cursos de tratamiento, donde cada curso termina al aumentar los corticoides o al colocar una nueva medicación inmunosupresora debido al empeoramiento clínico o aumento sostenido de las enzimas musculares. El tratamiento instaurado puede remitir, controlar parcialmente, o fracasar en controlar la enfermedad en cuanto se normalicen, estabilicen, o no modifiquen respectivamente tanto la clínica como las enzimas musculares. Se analizaron 20 ciclos, en 14 se logró la remisión, en cinco se controló parcialmente y en uno fracasó el tratamiento. La remisión se logró en un tiempo promedio de 139 ± 98 días y el control en un promedio de 160 ± 100 días. Excepto en una ocasión, todos los ciclos de tratamiento, independientemente del que fuera, remitieron o controlaron los síntomas, pero en el tiempo todos los pacientes recidivaron en su enfermedad.

Most studies about treatment of inflammatory myopathies consist of cross-sectional analyses that do not assess long-term efficacy. In the present study we describe the follow-up of seven patients with inflammatory myopathies, 5 polymyositis and 2 dermatomyositis. We describe their clinical features, follow-up, muscle enzyme levels, and treatment responses. We define the latter as treatment cycles, every one of which end when steroid doses need to be increased or a new immunosuppressive drug has to be added because of clinical worsening or sustained increases in muscle enzyme levels. Treatment can cause remission, partially control, or fail in achieving myositis improvement when it normalizes, stabilizes, or does not affect muscle enzymes or clinical features, respectively. We analyzed 20 cycles, in which remission was achieved in 14 cases, partial control in 5 instances, and treatment failure in one case. Remission occurred after an average of 139 ± 98 days, whereas partial control took place in 160 ± 100 days. Except in one case, all treatment cycles controlled or remitted the symptoms. However, in all patients the illness recurred with time.

The Newcastle Pediatric Mitochondrial Disease Scale: translation and cultural adaptation for use in Brazil / Escala Pediátrica de Doença Mitocondrial de Newcastle: tradução e adaptação cultural para uso no Brasil

ABSTRACT Objective The aim of this study was to translate and adapt the Newcastle Paediatric Mitochondrial Disease Scale (NPMDS) to Portuguese for use in Brazil. Methods The scale was applied in 20 pediatric patients with mitochondrial disease, in three groups: myopathy (n = 4); Leigh syndrome (n = 8); and encephalomyopathy (n = 8). Scores were obtained for the various dimensions of the NPMDS, and comparisons were drawn between the groups. Results There was a statistically significant difference between the myopathy group and the Leigh syndrome group (p = 0.0085), as well as between the myopathy and encephalomyopathy groups (p = 0.01). Conclusions The translation of the NPMDS, and its adaptation to the socioeconomic and cultural conditions in Brazil, make the NPMDS score useful as an additional parameter in the evaluation and monitoring of pediatric patients with MD in Brazil.

RESUMO Objetivo O objetivo do presente estudo foi realizar a tradução e adaptação da escala NPMDS para a população brasileira. Métodos A escala foi aplicada em 20 crianças e adolescentes com doença mitocondrial (DM) divididos em três grupos: miopatia (n=4), síndrome de Leigh (n=8) e encefalomiopatia (n=8). Obteve-se os escores separados das dimensões da escala NPMDS, foram realizadas comparações entre os escores da NPMDS nos diferentes grupos. Conclusão A tradução da escala NPMDS e sua adequação as condições socioeconômicas e culturais de nossa população tornam este instrumento um parâmetro adicional na avaliação e acompanhamento de pacientes pediátricos com DM.

Polimiositis secundaria a tuberculosis en un niño de 11 años / Polymyositis secondary to tuberculosis in an 11-year-old boy

Resumen:La polimiositis es una de las miopatías inflamatorias idiopáticas. Tiene una incidencia mundial estimada en 4 casos por cada millón de habitantes al año. Es considerada un diagnóstico de exclusión y se ha establecido una asociación con la infección por micobacterias. Se reporta el caso de un niño de 11 años de edad con polimiositis secundaria a tuberculosis. La polimiositis tuvo una adecuada respuesta a los corticosteroides, pero estos no fueron necesarios después del diagnóstico de una infección pulmonar por Mycobacterium tuberculosis. El tratamiento antifímico, sin la terapia con esteroides, permitió una resolución de ambas patologías y la evolución favorable del paciente.

Abstract:Polymyositis is one of the idiopathic inflammatory myopathies. It has an estimated worldwide incidence of 4 cases per million population per year. It is considered an exclusion diagnosis and a relationship with mycobacterial infection has been established. This article reports the case of an 11-year-old boy with polymyositis secondary to tuberculosis. Polymyositis had an adequate response to corticosteroids, but these were not needed after the diagnosis of a Mycobacterium tuberculosis lung infection. Anti-tuberculosis treatment without steroid therapy, allowed a resolution of both conditions and the favorable outcome of the patient.

Electrocardiographic changes in dermatomyositis and polymyositis / Alterações eletrocardiográficas em dermatomiosite e polimiosite

ABSTRACT Introduction: Cardiac involvement is frequent in inflammatory myopathies. Electrocardiogram (ECG) may show evidence of this involvement and its changes should be well-known and described. Objectives: Due to the lack of studies in the literature, we conducted an analysis of the ECG findings in patients with dermatomyositis (DM) and polymyositis (PM), comparing them with a control group. Methods: This cross-sectional study compared the ECG of 86 individuals with no rheumatic disorders (controls) with 112 patients (78 DM and 34 PM), during 2010 to 2013. The ECG findings between DM and PM were also compared. Results: Demographic characteristics, comorbidities and ECG abnormalities were similar between controls and patients (p > 0.05), except for a higher frequency of left ventricular hypertrophy (LVH) in patients (10.7% vs. 1.2%, p = 0.008). Demographic characteristics, comorbidities, clinical and laboratory manifestations, were also similar between the groups PM and DM, except for the presence of cutaneous lesions only in DM. One third of the patients had ECG abnormalities, which were more prevalent in PM than DM (50% vs. 24.4%, p = 0.008). LVH, left atrial enlargement, rhythm and conduction abnormalities were more frequent in PM than DM (p < 0.05 for all), especially the left anterior fascicular block. Conclusions: We showed distinct ECG changes between DM and PM and a higher frequency of LVH in patients compared to controls. Investigation of cardiac involvement should be considered even in asymptomatic patients, especially PM. Further studies are necessary in order to determine the correlation of ECG findings with other complementary tests, clinical manifestations, disease activity and progression to other cardiac diseases.

RESUMO Introdução: Acometimento cardíaco nas miopatias inflamatórias é frequente. Eletrocardiograma (ECG) pode mostrar indícios desse acometimento e suas alterações devem ser bem conhecidas e descritas. Objetivos: Devido à escassez de trabalhos na literatura, analisamos as alterações de ECG em pacientes com dermatomiosite (DM) e polimiosite (PM) e as comparamos com um grupo controle. Métodos: Este estudo transversal comparou ECGs de 86 indivíduos sem doenças reumatológicas (controles) com 112 pacientes (78 DM e 34 PM), de 2010 a 2013. Também comparamos os ECGs entre DM e PM. Resultados: Características demográficas, comorbidades e alterações de ECG foram semelhantes entre controles e pacientes (p > 0,05), exceto pela maior frequência de sobrecarga de ventrículo esquerdo (SVE) nos pacientes (10,7% vs. 1,2%; p = 0,008). Características demográficas, comorbidades, manifestações clínicas e laboratoriais também foram semelhantes entre os grupos PM e DM, exceto por lesões cutâneas apenas em pacientes com DM. Um terço dos pacientes apresentou alterações de ECG, que foram mais prevalentes em PM do que em DM (50% vs. 24,4%, p = 0,008). Sobrecarga de câmaras esquerdas (SCE), distúrbios do ritmo e da condução foram mais encontrados em PM do que em DM (p < 0,05 para todos), sobretudo o bloqueio divisional do ramo anterossuperior. Conclusões: Encontramos alterações distintas de ECG entre PM e DM e frequência aumentada de SVE em pacientes quando comparados com controles. Investigação do acometimento cardíaco nessas doenças deve ser considerada mesmo em pacientes assintomáticos, especialmente em se tratando de PM. Mais estudos são necessários para correlacionar os achados de ECG com outros exames complementares, manifestações clínicas, atividade das miopatias e evolução para outras doenças cardíacas.

Variabilidad en la determinación de fracción grasa muscular en resonancia magnética utilizando la técnica de Dixon / Variability in magnetic resonance quantification of muscle fat fraction using Dixon's technique

Abstract. Muscle MRI has emerged as a valuable tool in the diagnosis of neuromuscular-disorders. The Dixon fat-water separation technique allows objective intra-muscular fat quantification. There are few reports concerning measurement standardisation with Dixon technique. The objective of this study was to evaluate the variability in fat quantification using Dixon's technique in a cohort of patients with congenital myopathies, by analysing intra-segment, intra-muscle, and inter-muscle variability of 60 muscles in each patient. Whole body MRI was performed on 31 patients, 23 with congenital myopathies and 8 healthy controls, aged between 10 months and 35 years old, from January 2014 to June 2016. The mean fat-fraction in healthy patients was around 5%, with less than 2% intra-muscle variability. An intra-muscle variability between 3.1-7.8% was estimated in patients with congenital myopathies. It may be concluded that there is high intra- and inter-muscle fat-fraction variability among patients with congenital myopathies, and this is an observation that should be incorporated in the analysis of fat replacement.

Resumen. La resonancia magnética muscular ha emergido como una valiosa herramienta de apoyo diagnóstico en enfermedades neuromusculares. La técnica de Dixon permite objetivar la fracción grasa muscular, pero no existe consenso sobre la estandarización de estas mediciones. El objetivo de este estudio fue evaluar la variabilidad en la determinación de fracción grasa utilizando la técnica de Dixon, estudiando la variabilidad intrasegmentaria, intramuscular e intermuscular en 60 músculos por paciente. Se realizó RM de cuerpo completo a 31 pacientes: 23 con miopatía congénita y 8 controles, entre 10 meses y 35 años de edad, desde enero del 2014 a junio del 2016. En pacientes sanos se estimó una fracción grasa promedio cercana al 5%, con una variabilidad intramuscular inferior al 2%. En pacientes con miopatías congénitas existe una variabilidad entre el 3,1-7,8%. El estudio permite concluir que existe una alta variabilidad intra e intermuscular en pacientes miopáticos, que no se observa en pacientes sanos.