Mitochondrial disorders: Challenges in diagnosis & treatment.

Mitochondrial dysfunctions are known to be responsible for a number of heterogenous clinical presentations with multi-systemic involvement. Impaired oxidative phosphorylation leading to a decrease in cellular energy (ATP) production is the most important cause underlying these disorders. Despite significant progress made in the field of mitochondrial medicine during the last two decades, the molecular mechanisms underlying these disorders are not fully understood. Since the identification of first mitochondrial DNA (mtDNA) mutation in 1988, there has been an exponential rise in the identification of mtDNA and nuclear DNA mutations that are responsible for mitochondrial dysfunction and disease. Genetic complexity together with ever widening clinical spectrum associated with mitochondrial dysfunction poses a major challenge in diagnosis and treatment. Effective therapy has remained elusive till date and is mostly efficient in relieving symptoms. In this review, we discuss the important clinical and genetic features of mitochondrials disorders with special emphasis on diagnosis and treatment.

Espectro clínico de pacientes con hallazgos histopatológicos y/o moleculares compatibles con enfermedad mitochondrial / Clinical spectrum of patients with histopathological and/or molecular findings compatible with mitochondrial disease

Objetivo: Describir el espectro clínico de pacientes con diagnóstico definitivo de Enfermedad Mitocondrial, y su correlación con hallazgos bioquímicos, neuroimagenológicos, neuropatológicos, y moleculares. Método: Se revisaron las historias clínicas de pacientes con Enfermedad Mitocondrial evaluados durante el período 1990-2011. Resultados: Se incluyeron 41 pacientes, con una edad media inicial de 3,7 años. Identificamos cuatro grupos:1) Síndromes clásicos (65%): a) MELAS del inglés “Mitochondrial encephalomyopathy, lacticacidosis, and stroke-like episodes”, (diez), b) Síndrome de Leigh (diez) c) Síndrome de Kearns –Sayre (cinco), d) PEO del inglés “Progressive External Ophthalmoplegia” plus (OEP plus) (dos), 2) Miopatía: nueve (21,5%) 3) Encefalomiopatías inespecíficas: cinco (12%). Se realizó biopsia muscular en 37 pacientes. Un 70% evidenció fibras rojo rasgadas, cuatro (10,5%) fibras citocromo oxidasa negativas y ocho (14,7%) incremento de la actividad oxidativa subsarcolemal y en la microscopia electrónica alteraciones del tamaño y número de mitocondrias. En 14 se completaron estudios moleculares: Siete presentaron una mutación puntual A3243G en el ADN mitocondrial (MELAS), un paciente una mutación en el ADN mitocondrial A1351G (Síndrome de Leigh) y un paciente una deleción del ADN mitocondrial (OEP plus). Conclusiones: Se pudo corroborar la existencia en nuestro medio de síndromes asociados a patología mitocondrial tradicionalmente reconocidos. Un grupo de pacientes con encefalomiopatías denominadas inespecíficas presentaron un cuadro clínico variable, hallazgos de laboratorio y de imágenes poco orientadores y fue la sospecha de una enfermedad mitocondrial lo que nos llevó a realizar la biopsia que finalmente fue diagnóstica. Es posible que este grupo sea más numeroso y las limitaciones que implica realizar una biopsia muscular se facilite con los estudios moleculares.

Pediatric-Onset Dystonia Associated with Bilateral Striatal Necrosis and G14459A Mutation in a Korean Family: A Case Report

We describe a Korean family presenting with pediatric-onset, progressive, generalized dystonia with bilateral striatal necrosis and the homoplasmic G14459A mutation in the mitochondrial ND6 gene. The G14459A mutation has been reported in families presenting with Leber hereditary optic neuropathy (LHON) alone, LHON plus dystonia, or pediatric-onset dystonia. The proband had shown dysarthria, progressive generalized dystonia, and spasticity at 5 yr. Brain MRI demonstrated bilateral striatal necrosis. Additional investigation of family members revealed the presence of homoplasmic G14459A mutation in asymptomatic individuals. The clinical manifestation of the homoplasmic G14459A mtDNA mutation within the same family showed asymptomatic or pediatric-onset dystonia, without optic neuropathy. This study reemphasizes that the G14459A mutation is a candidate mutation for maternally inherited dystonia, regardless of optic neuropathy, and supports the hypothesis that nuclear genes may play a role in modifying the clinical expression of mitochondrial disease.

Primary Pulmonary Hypertension as a Manifestation of Adult Multi-System Mitochondrial Disorder

No abstract available.

Neuroftalmología de las Enfermedades Mitocondriales / Neurophthalmology of Mitochondrial Diseases

Se realiza una revisión del tema: Neuroftalmología de las enfermedades mitocondriales con el objetivo de analizar las alteraciones neuroftalmológicas que con mayor frecuencia aparecen en estas entidades que no son más que la expresión de una mutación en el ADN mitocondrial, así como abordar el comportamiento genético de las mismas. Para ello nos auxiliamos de diversos trabajos publicados por doctores cubanos y extranjeros que ayudan a arribar a la conclusión que la neuropatía óptica debe ser considerada un marcador de la enfermedad mitocondrial, que debemos pensar en ella cuando estamos ante un paciente con retinopatía pigmentaria asociada a una enfermedad sistémica o neurológica indefinida y que una mutación puntual en el ADN mitocondrial será heredada de forma materna y defectos en el ADN nuclear, aún afectando éstos a la mitocondria, serán trasmitidos por la clásica herencia Mendeliana.

There has been done a revision of the topic: Neurophthalmology of mitochondrial disease with the purpose to analize the neurophthalmological alterations that appear with more frequency in these entities that are the expression a mutation in mitochondrial DNA, as well as to tackle the genetic behaviour of it. To do this we consulted different published papers of Cuban and foreign doctors that help us to arrive to the conclusion that optic neuropathy should be consider as a of mitochondrial disease, that we have to think about it when having a patient with pigmentary retinopathy associated to a indefinite sistemic or neurological disease and that because of a punctual mutation in the mitochondrial DNA will be inherited maternally and defects in the nuclear DNA, even affecting it to the mitochondrion, will be transmitted by classic Mendelian heredity.

Síndrome psicótica evoluindo com demência como manifestação clinica de deleção do DNA mitocondrial / Psycothic syndrome developing into dementia as a clinical manifestation of mitochondrial DNA deletion

As manifestações das doenças mitocondriais são variadas, acometendo, mais freqüentemente, órgãos com alto metabolismo aeróbico em que são mais abundantes, como, por exemplo, o sistema nervoso. O início dos sintomas em geral é observado na infância havendo relatos de início na idade adulta. Apresentamos caso atípico de doença mitocondrial associada à deleção do DNA mitocondrial em um homem de 39 anos com sintomas psiquiátricos configuraram quadro clínico inicial e somente 12 anos após o início dos sintomas surgiram alterações neurológicas. O diagnóstico da doença mitocondrial foi confirmado por biópsia de músculo sendo documentada deleção do DNA mitocondrial.

The manifestations of mitochondrial disease are variable, affecting more frequently the organs with high aerobic metabolism in which they are more abundant, for example the nervous system. The beginning of symptoms in general is observed at chilhood, but some patients presented on adult age. We present an atypical case associated with mitochondrial DNA deletion. A 39-years-old man with psychiatric symptoms that configured initial clinical picture and only after 12 years of the beginning of symptoms neurological alterations became noticeable. The diagnosis of mitochondrial illness was confirmed by muscle biopsy being documented mitochondrial DNA deletion.

Liver mitochondrial dysfunction and oxidative stress in the pathogenesis of experimental nonalcoholic fatty liver disease

Oxidative stress and hepatic mitochondria play a role in the pathogenesis of nonalcoholic fatty liver disease. The aim of the present study was to evaluate the role of hepatic mitochondrial dysfunction and oxidative stress in the pathogenesis of the disease. Fatty liver was induced in Wistar rats with a choline-deficient diet (CD; N = 7) or a high-fat diet enriched with PUFAs-omega-3 (H; N = 7) for 4 weeks. The control group (N = 7) was fed a standard diet. Liver mitochondrial oxidation and phosphorylation were measured polarographically and oxidative stress was estimated on the basis of malondialdehyde and glutathione concentrations. Moderate macrovacuolar liver steatosis was observed in the CD group and mild liver steatosis was observed in the periportal area in the H group. There was an increase in the oxygen consumption rate by liver mitochondria in respiratory state 4 (S4) and a decrease in respiratory control rate (RCR) in the CD group (S4: 32.70 ± 3.35; RCR: 2.55 ± 0.15 ng atoms of O2 min-1 mg protein-1) when compared to the H and control groups (S4: 23.09 ± 1.53, 17.04 ± 2.03, RCR: 3.15 ± 0.15, 3.68 ± 0.15 ng atoms of O2 min-1 mg protein-1, respectively), P < 0.05. Hepatic lipoperoxide concentrations were significantly increased and the concentration of reduced glutathione was significantly reduced in the CD group. A choline-deficient diet causes moderate steatosis with disruption of liver mitochondrial function and increased oxidative stress. These data suggest that lipid peroxidation products can impair the flow of electrons along the respiratory chain, causing overreduction of respiratory chain components and enhanced mitochondrial reactive oxygen species. These findings are important in the pathogenesis of nonalcoholic fatty liver disease.

Compromiso multisistémico: ¿y si fuera una enfermedad mitocondrial / Multisystemic involvement: and if it was a mitochondrial disease?

Las mitocondrias como organelos subcelulares claves en la generación de la energía son esenciales para la supervivencia de la vida humana. Sus alteraciones conocidas en la actualidad como enfermedades o citopatías mitocondriales se han constituido en la última década en un área de acelerado desarrollo que involucra a todas las especialidades de la medicina. Focos de estudio de especial interés son la herencia "no tradicional" de estos trastornos con un doble control genético (nuclear y mitocondrial); la expresión variable de estas enfermedades en distintos tejidos (multisistémicas o multitisulares) y el creciente diagnóstico de estos cuadros que parecen ser más frecuentes.