Refractory Rickets

Nutritional rickets, caused by vitamin D and/or calcium deficiency is by far the most common cause of rickets. In resource-limited settings, it is therefore not uncommon to treat rickets with vitamin D and calcium. If rickets fails to heal and/or if there is a family history of rickets, then refractory rickets should be considered as a differential diagnosis. Chronic low serum phosphate is the pathological hallmark of all forms of rickets as its low concentration in extracellular space leads to the failure of apoptosis of hypertrophic chondrocytes leading to defective mineralisation of the growth plate. Parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) control serum phosphate concentration by facilitating the excretion of phosphate in the urine through their action on the proximal renal tubules. An increase in PTH, as seen in nutritional rickets and genetic disorders of vitamin D-dependent rickets (VDDRs), leads to chronic low serum phosphate, causing rickets. Genetic conditions leading to an increase in FGF23 concentration cause chronic low serum phosphate concentration and rickets. Genetic conditions and syndromes associated with proximal renal tubulopathies can also lead to chronic low serum phosphate concentration by excess phosphate leak in urine, causing rickets. In this review, authors discuss an approach to the differential diagnosis and management of refractory rickets

Primer reporte en Argentina de variante patógena en DMP1 asociada a raquitismo hipofosfatémico autosómico recesivo / First report in Argentina of a pathogenic DMP1 variant associated with autosomal recessive hypophosphatemic rickets

El raquitismo hipofosfatémico hereditario es una condición genética asociada con una mineralización ósea alterada causada por la deficiencia de fosfato. Produce deformidad esquelética y retraso del crecimiento en la infancia. Se describen diferentes patrones de herencia según el locus involucrado. Dado el solapamiento de los fenotipos y la dificultad en analizar genealogías reducidas, los estudios moleculares son importantes para establecer la causa genética y realizar el abordaje familiar. La forma recesiva del raquitismo hipofosfatémico (ARHR, OMIM #241520) es una condición extremadamente poco frecuente reportada en familias de origen europeo y de Oriente Medio. Las mutaciones con pérdida de función del gen DMP1 (dentin matrix acidic phosphoprotein 1) se asocian al raquitismo hipofosfatémico hereditario tipo 1. En este artículo presentamos el primer reporte de una familia argentina con raquitismo hipofosfatémico hereditario por mutación en DMP1

Hereditary hypophosphatemic rickets is a genetic condition associated with impaired bone mineralization caused by phosphate deficiency. It results in skeletal deformity and growth retardation in early childhood. Different inheritance patterns have been described according to the locus involved. Given the phenotypic overlapping and the difficulty in analyzing reduced genealogies, molecular studies are important to establish the genetic cause and implement a family-centered approach. The autosomal recessive form of hypophosphatemic rickets (ARHR, OMIM 241520) is an extremely rare condition reported in families of European and Middle Eastern descent. Loss-of-function mutations in the DMP1 (dentin matrix acidic phosphoprotein 1) gene are associated with hereditary hypophosphatemic rickets type 1. In this article, we describe the first report of an Argentine family with hereditary hypophosphatemic rickets due to a mutation in the DMP1 gene.

Prevalence and Correlates of Vitamin D Deficiency Among Children and Adolescents From a Nationally Representative Survey in India

Objective: To evaluate the prevalence of vitamin D deficiency (VDD) and its correlates among apparently healthy children and adolescents. Methods: We carried out a secondary analysis of data of Comprehensive National Nutrition Survey 2016-18 to analyze the pre-valence and predictors of VDD among Indian children and adolescents. Results: The over-all prevalence of VDD in preschool children (1-4 years), school age (5-9 years) children, and adolescents (10-19 years) was 13.7%, 18.2%, and 23.9%, respectively. Age, living in urban area, and winter season were significantly associated with VDD. Vegetarian diet and high-income households were the main risk factors observed in 5-19 years age category. Female sex and less than three hour of physical activity/week were independent risk factors among adolescents. Conclusion: The prevalence and determinants of VDD across different age-groups are reported, and these should be interpreted and addressed to decrease the burden of VDD in India.

Raquitismo hipofosfatémico familiar ligado al cromosoma X: Reporte de Caso

El Fósforo es regulado por el riñón y el sistema óseo orquestado principalmente por la acción de la parathormona (PTH) y una molécula recientemente descrita como el factor de crecimiento fibroblástico 23 (FGF-23) . Presentamos los casos de dos pacientes madre-hijo con Raquitismo hipofosfatémico ligado al cromosoma X. Se realizó el estudio genético identificándose una mutación en el Gen PHEX: variante patogénica tipo splicing en hemicigosis: mutación previamente descrita como HGMD CS126536. El Raquitismo Hipofosfatémico forma parte de un grupo de tubulopatías caracterizadas hiperfosfaturia. La mutación del gen PHEX con pérdida de función conduce al aumento de FGF-23. PHEX degrada el FGF-23 en fragmentos inactivos, evitando la excreción excesiva de fosfatos y el desarrollo de hipofosfatemia. En un paciente con hipofosfatemia no dependiente de la hormona PTH o de la vitamina D y de presentación familiar debe considerarse el diagnóstico de Raquitismo hipofosfatémico ligado al cromosoma X.

Phosphate is regulated by the kidneys and the osseus system, mainly due to the action of parathyroid hormone (PTH) and a recently described molecule, fibroblast growth factor 23 (FGF-23). We present the cases of two patients, mother and son with X-chromosome linked hypophosphatemic rickets. The genetic study was performed, and a mutation in the PHEX gene was identified, a splicing type pathogenic variant in hemizygosis. This mutation was previously described as HGMD CS126536. Hypophosphatemic rickets belongs to a group of tubulopathies characterized by hyperphosphaturia. PHEX gene mutation with function loss leads to increased FGF-23 levels. PHEX degrades FGF-23 into inactive fragments, preventing excessive phosphate excretion and the development of hypophosphatemia. In patients with PTH or vitamin D non- dependent hypophosphatemia, a diagnosis of X-chromosome linked hypophosphatemic rickets should be considered.

Value of serum fibroblast growth factor 23 in diagnosis of hypophosphatemic rickets in children / 中国当代儿科杂志

OBJECTIVES@#To study the value of serum fibroblast growth factor 23 (FGF23) in the diagnosis of hypophosphatemic rickets in children.@*METHODS@#A total of 28 children who were diagnosed with hypophosphatemic rickets in Children's Hospital of Nanjing Medical University from January 2016 to June 2021 were included as the rickets group. Forty healthy children, matched for sex and age, who attended the Department of Child Healthcare of the hospital were included as the healthy control group. The serum level of FGF23 was compared between the two groups, and the correlations of the serum FGF23 level with clinical characteristics and laboratory test results were analyzed. The value of serum FGF23 in the diagnosis of hypophosphatemic rickets was assessed.@*RESULTS@#The rickets group had a significantly higher serum level of FGF23 than the healthy control group (P<0.05). In the rickets group, the serum FGF23 level was positively correlated with the serum alkaline phosphatase level (rs=0.38, P<0.05) and was negatively correlated with maximum renal tubular phosphorus uptake/glomerular filtration rate (rs=-0.64, P<0.05), while it was not correlated with age, height Z-score, sex, and parathyroid hormone (P>0.05). Serum FGF23 had a sensitivity of 0.821, a specificity of 0.925, an optimal cut-off value of 55.77 pg/mL, and an area under the curve of 0.874 in the diagnosis of hypophosphatemic rickets (P<0.05).@*CONCLUSIONS@#Serum FGF23 is of valuable in the diagnosis of hypophosphatemic rickets in children, which providing a theoretical basis for early diagnosis of this disease in clinical practice.

Sunlight Exposure vs Oral Vitamin D Supplementation for Prevention of Vitamin D Deficiency in Infancy: ARandomized Controlled Trial

Objective: To compare the efficacy of sunlight exposure and oral vitamin D3 supplementation to achieve vitamin D sufficiency in infants at 6 months of age. Design: Open-label randomized controlled trial. Setting: Public hospital in Northern India (28.7°N). Participant: Breastfed infants at 6-8 weeks of age. Intervention: Randomized to receive sunlight exposure (40% body surface area for a minimum of 30 minutes/week) or oral vitamin D3 supplementation (400 IU/day) till 6 months of age. Outcome: Primary - proportion of infants having vitamin D sufficiency (>20 ng/mL). Secondary - proportion of infants developing vitamin D deficiency (<12ng/mL) and rickets in both the groups at 6 months of age. Results: Eighty (40 in each group) infants with mean (SD) age 47.8 (4.5) days were enrolled. The proportion of infants with vitamin D sufficiency increased after intervention in the vitamin D group from 10.8% to 35.1% (P=0.01) but remained the same in sunlight group (13.9%) and was significant on comparison between both groups (P=0.037). The mean (SD) compliance rate was 72.9 (3.4)% and 59.7 (23.6)% in the vitamin D and sunlight group, respectively (P=0.01). The geometric mean (95% CI) serum 25(OH) D levels in the vitamin D and sunlight group were 16.23 (13.58-19.40) and 11.89 (9.93-14.23) ng/mL, respectively; (P=0.02), after adjusting baseline serum 25(OH)D with a geometric mean ratio of 1.36 (1.06-1.76). Two infants in sunlight group developed rickets. Conclusion: Oral vitamin D3 supplementation is more efficacious than sunlight in achieving vitamin D sufficiency in breastfed infants during the first 6 months of life due to better compliance.

New treatments for rare bone diseases: hypophosphatemic rickets/osteomalacia

Abstract Phosphorus is one of the most abundant minerals in the human body; it is required to maintain bone integrity and mineralization, in addition to other biological processes. Phosphorus is regulated by parathyroid hormone, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and fibroblast growth factor 23 (FGF-23) in a complex set of processes that occur in the gut, skeleton, and kidneys. Different molecular mechanisms - overproduction of FGF-23 by tumors responsible for oncogenic osteomalacia, generation of an FGF-23 mutant that is resistant to cleavage by enzymes, and impaired FGF-23 degradation due to a reduction in or loss of the PHEX gene - can lead to FGF-23-stimulating activity and the consequent waste of urinary phosphate and low levels of 1,25(OH)2D3. Conventional treatment consists of multiple daily doses of oral phosphate salts and vitamin D analogs, which may improve radiographic rickets but do not normalize growth. Complications of the conventional long-term treatment consist of hypercalcemia, hypercalciuria, nephrolithiasis, nephrocalcinosis, impaired renal function, and potentially chronic kidney disease. Recently, burosumab, an antibody against FGF-23, was approved as a novel therapy for children and adults with X-linked hypophosphatemia and patients with tumor-induced osteomalacia. Burosumab showed good performance in different trials in children and adults. It increased and sustained the serum phosphorus levels, decreased the rickets severity and pain scores, and improved mineralization. It offers a new perspective on the treatment of chronic and disabling diseases. Arch Endocrinol Metab. 2022;66(5):658-65

Dental and Endodontic Management in a Patient with Familial X-Linked Hypophosphatemic Rickets

ABSTRACT: The term rickets refers to insufficient or retarded mineralization of the osteoide matrix. X-linked hypophosphatemic (XLH) rickets is a rare genetic disorder characterized by biochemical changes in bone mineralization due to inactivation of the phosphate regulating gene and primary defect of the osteoblasts. The aim of this article was to report a clinical case of XLH, its oral manifestations, periapical changes and dental management. A 31-year old woman female patient was referred to the school of dentistry with pain and sensitivity in the teeth. She had a childhood history of rickets, hypophosphatemia and alteration in Vitamin D. In the oral exam, enamel hypoplasia, microdontia, fistula, caries and periapical lesions and periodontal disease were diagnosed. The radiographic and tomographic exams exhibited the presence of periapical lesions involving various teeth with radiolucent images, suggestive of granuloma or periapical cysts. The treatme nt prioritized the urgency of eliminating pain and removing the foci of infection. Endodontic treatment began in the teeth that had fistula or periapical lesions and in parallel, oral hygiene guidance was provided and periodontal treatment was performed. There was an improvement in the clinical condition with reduction in inflammation and mobility of the teeth. Dentists and health professionals must evaluate the patient as a whole, considering the relations between systemic and oral health. Knowledge of systemic diseases associated with rickets and their characteristics is essential for making a correct oral diagnosis and planning the dental treatment.

RESUMEN: El término raquitismo se refiere a la mineralización insuficiente o retardada de la matriz osteoide. El raquitismo hipofosfatémico ligado al cromosoma X (XLH) es un trastorno genético caracterizado por cambios bioquímicos en la mineralización ósea debido a la inactivación del gen regulador del fosfato y al defecto primario de los osteoblastos. El objetivo de este artículo fue reportar un caso clínico de XLH, sus manifestaciones orales, cambios periapicales y manejo dental. La paciente, una mujer de 31 años, acudió a la Clínica de Semiología de la UFPR con dolor y sensibilidad en varios dientes. Tenía antecedentes infantiles de raquitismo, hipofosfatemia y alteración de la vitamina D. En el examen oral se diagnosticó hipoplasia del esmalte, microdoontia, fístula, caries y lesiones periapicales y enfermedad periodontal. Los exámenes radiográficos y tomográficos mostraron la presencia de lesiones periapicales en varios dientes con imágenes radiolúcidas, sugestivas de granuloma o quistes periapicales. El tratamiento priorizó la urgencia de eliminar el dolor y remover los focos de infección. Se inició tratamiento de endodoncia en los dientes que presentaban fístula o lesiones periapicales y paralelamente se brindó orientación de higiene oral y se realizó tratamiento periodontal. Hubo una mejoría en la condición clínica con reducción de la inflamación y movilidad de los dientes. Los odontólogos y profesionales de la salud deben evaluar al paciente como un todo, teniendo en cuenta las relaciones entre salud sistémica y oral. El conocimiento de las enfermedades sistémicas asociadas al raquitismo y sus características es fundamental para realizar un correcto diagnóstico oral y planificar el tratamiento odontológico.

La accidentada historia del descubrimiento de la vitamina D, en su primer centenario / The checkered history of the discovery of vitamin D, in its first centenary

El año 2022 marca el primer centenario del descubrimiento de la vitamina D, hallazgo que recompensó la prolongada búsqueda de la causa del raquitismo, su prevención y tratamiento. Al mismo tiempo puso en marcha importantes investigaciones relaciona-das con su biotransformación y el mecanismo de su acción antirraquítica, además de estudios sobre diversos efectos biológicos sin relación directa con su papel en la salud ósea. Esta breve revisión se limitará a delinear la prehistoria de la vitamina D y los diversos estudios, básicos y clínicos, que condujeron a su descubrimiento y caracterización química. (AU)

The year 2022 marks the centenary of the discovery of vitamin D, a breakthrough that rewarded the long search for the cause of rickets, its prevention and treatment. At the same time, it launched important investigations related to its biotransformation and the mechanism of its antirachitic action, as well as studies on various biological effects without direct relation to its role in bone health. This brief review will be limited to an outline of the prehistory of vitamin D and the various basic and clinical studies that led to its discovery and chemical characterization. (AU)

Guideline for the diagnosis and management of hypophosphatemic rickets/osteomalacia / 中华内分泌代谢杂志

Hypophosphatemic rickets/osteomalacia is a group of rare chronic metabolic bone diseases, which has detrimental impact on the growth, mobility, and life quality of the patients. Because of its rarity, the public awareness remains low, so does in general physician, which leads to delayed diagnosis and treatment. With a vision to standardize the diagnosis and treatment of hypophosphatemic rickets/osteomalacia, Chinese Society of Endocrinology and Chinese Society of Osteoporosis and Bone Mineral Research convened a national group of experts to compose this guideline based on current evidence, which covered the pathogenesis, diagnosis, treatment and management of hypophosphatemic rickets/osteomalacia. In summary, this work outlines recommendations for clinicians, aiming to improve the management of hypophosphatemic rickets/osteomalacia in China.

X-linked hypophosphatemic rickets: a new mutation / Raquitismo hipofosfatêmico ligado ao X: uma nova mutação

Abstract Phosphopenic rickets may be caused by mutations in the PHEX gene (phosphate regulating endopeptidase homolog X-linked). Presently, more than 500 mutations in the PHEX gene have been found to cause hypophosphatemic rickets. The authors report a clinical case of a 4-year-old girl with unremarkable family history, who presented with failure to thrive and bowing of the legs. Laboratory tests showed hypophosphatemia, elevated alkaline phosphatase, normal calcium, mildly elevated PTH and normal levels of 25(OH)D and 1.25(OH)D. The radiological study showed bone deformities of the radius and femur. Clinical diagnosis of phosphopenic rickets was made and the genetic study detected a heterozygous likely pathogenic variant of the PHEX gene: c.767_768del (p.Thr256Serfs*7). This variant was not previously described in the literature or databases. Knowledge about new mutations can improve patient's outcome. Genetic analysis can help to establish a genotype-phenotype correlation.

Resumo O raquitismo fosfopênico pode ser causado por mutações no gene PHEX (ligado ao X do homólogo da endopeptidase que regula o fosfato). Atualmente, mais de 500 mutações no gene PHEX causam raquitismo hipofosfatêmico. Os autores relatam um caso clínico de uma menina de 4 anos com histórico familiar sem relevância, que apresentou falha no crescimento e arqueamento das pernas. Os exames laboratoriais mostraram hipofosfatemia, fosfatase alcalina elevada, cálcio normal, PTH levemente elevado e níveis normais de 25(OH)D e 1,25(OH)D. O estudo radiológico mostrou deformidades ósseas no rádio e no fêmur. O diagnóstico clínico do raquitismo fosfopênico foi realizado e o estudo genético detectou uma provável variante patogênica heterozigótica do gene PHEX: c.767_768del (p.Thr256Serfs*7). Esta variante não foi descrita anteriormente na literatura ou nas bases de dados. O conhecimento sobre novas mutações pode melhorar o desfecho de pacientes. A análise genética pode ajudar a estabelecer uma correlação genótipo-fenótipo.

Deficiencia de vitamina D asociada a hiperfosfatemia en niños / Vitamin D deficiency associated with hyperphosphatemia in children

RESUMEN Los niños con deficiencia de vitamina D pueden tener fósforo normal o alto a pesar de tener una prueba de hormona paratiroidea (PTH) elevada. El pseudohipoparatiroidismo (PHP) se caracteriza por cursar con hiperfosfatemia. La similitud que puede ocurrir entre la deficiencia de vitamina D asociada a hiperfosfatemia y el PHP hace importante revisar reportes de casos de deficiencia de vitamina D asociada a hiperfosfatemia para entender por qué puede ocurrir esta asociación y cuál es la relevancia de estudiar el nivel de vitamina D en niños con sospecha de PHP. El objetivo de esta revisión fue identificar reportes de niños con deficiencia de vitamina D asociada a hiperfosfatemia y discutir los mecanismos de esta asociación. Se identificaron reportes de 7 casos en niños. La deficiencia de vitamina D reduciría la respuesta fosfatúrica ante una PTH elevada. Se concluye que es importante descartar deficiencia de vitamina D en todo niño con sospecha de PHP.

ABSTRACT Children with vitamin D deficiency can have normal or high phosphorus despite having a high parathyroid hormone test (PTH). Pseudohypoparathyroidism (PHP) is characterized by hyperphosphatemia. The similarity that can occur between vitamin D deficiency associated with hyperphosphatemia and PHP makes it important to review case reports of vitamin D deficiency associated with hyperphosphatemia to understand why this association may occur and what is the relevance of studying the vitamin D level in children with suspected PHP. The aim of this review was to identify reports of children with vitamin D deficiency associated with hyperphosphatemia and to discuss the mechanisms of this association. Reports of 7 children cases were identified. Vitamin D deficiency could reduce the phosphaturic response to elevated PTH. It is concluded that it is important to rule out vitamin D deficiency in all children with suspected PHP.

Raquitismo vinculado al uso de fórmulas elementales: Reporte de caso / Rickets associated to the use of elemental formula: A case report

El raquitismo afecta la diferenciación y mineralización del cartílago de crecimiento como consecuencia, en última instancia, de una alteración en los niveles de fósforo y/o calcio. El secundario a la deficiencia de vitamina D es la forma más frecuente (raquitismo carencial). Las manifestaciones clínicas durante los primeros años de vida suelen comprometer en forma más marcada las epífisis de los huesos.Se describe el caso de un lactante de 8 meses con diagnóstico de alergia a la proteína de la leche de vaca que presentó múltiples fracturas patológicas mientras se encontraba bajo tratamiento con fórmulas lácteas a base de aminoácidos. Se efectuó el diagnóstico de raquitismo hipofosfatémico por deficiencia de fósforo y, tras 3 meses de tratamiento con sales de fosfato, calcio, calcitriol, el abandono paulatino de la leche elemental y el descenso gradual de la medicación antiácida, el paciente evolucionó con curación clínico-radiológica del cuadro

The rickets is a disease that affects the differentiation and mineralization of the growth cartilage, as an ultimate consequence of a balance loss in calcium and phosphate levels. Vitamin D deficiency is the most common cause of the rickets (nutritional rickets). Its clinical manifestation during the first years of life involves long bones epiphysis in a more severe way.We report an 8-month-old infant who was diagnosed with cow ́s milk protein allergy and suffered from multiple fractures while receiving elemental formula as part of his treatment. The final etiology was hypophosphatemic rickets secondary to phosphate deficiency, and after 3 months of phosphate, calcium and calcitriol supplementation, in addition to the gradually reduction of the proportion of elemental formula intake and the decline of the antacid doses, clinical and radiological heal was achieved.

Arte, historia y endocrinología / Art, history and endocrinology

Las enfermedades han sido representadas en el arte desde tiempos remotos. Las obras pictóricas muchas veces nos muestran trastornos que aún no se constituían como una entidad. Observar estos cuadros a la luz de la historia de las enfermedades nos da una perspectiva enriquecedora que nos ayuda a entender mejor dichas patologías. Se comenta un caso clínico endocrinológico pediátrico, la historia probable y su descripción física. Se revisa la historia de cómo se llegó a dilucidar la enfermedad y las claves de su tratamiento.

Diseases have been represented in art since ancient times. Paintings often show us disorders that had not yet been described as a pathological entity. Looking at these pictures in the light of the history of the diseases gives us an enriching perspective that helps us to better understand those pathologies. On this background a pediatric endocrinological clinical case, the most probable history and the features of the physical examination are discussed. The history of how the disease was uncovered and the keys of its treatment are reviewed.

Autosomal recessive hypophosphatemic rickets 1 caused by DMP1 mutation: one pedigree study / 中华内分泌代谢杂志

In the present study, the clinical features of a patient with autosomal recessive hypophosphatemic rickets 1 caused by dentin matrix protein 1(DMP1)gene mutation and her family members were investigated. DMP1 gene from peripheral blood was sequenced by Sanger sequencing, and the known mutation was verified among her family members and 250 healthy populations. The proband was a 42-year-old female with bone deformity of both lower limbs, bone pain, and short stature. The results of X-rays and laboratory examination were consistent with the hypophosphatemic rickets reported before. A homozygous mutation(c.2T> C)in DMP1 was identified by Sanger sequencing in the proband, her son and daughter were heterozygous for c. 2T> C.

Relationship of serum vitamin D with liver disease severity and bone abnormalities in cholestatic children

@#<p style="text-align: justify;"><strong>Background:</strong> Vitamin D deficiency occurs in 10% to 36% of children with cholestasis. The relationship between serum vitamin D levels, severity of liver disease and bone abnormalities in children has not been extensively investigated.</p><p style="text-align: justify;"><strong>Objective:</strong> To determine serum vitamin D levels and its association with liver disease severity and presence of radiographic rickets in children with cholestasis.</p><p style="text-align: justify;"><strong>Methods:</strong> Children aged 0-10 years with cholestasis underwent serum 25-hydroxyvitamin D levels (25-[OH]D) determination, radiographs of wrists and knees and liver function tests. Liver disease severity was evaluated using the Child-Pugh score. Radiographs were assessed using Thacher Rickets Severity Score. Data were analyzed using odds ratio and Spearman's correlation coefficient.</p><p style="text-align: justify;"><strong>Results:</strong> We included 51 children [Mean (SD) age: 5 (6) months, 63% are males], mostly with biliary atresia (51%). Forty-seven (92%) had serum 25-(OH)D deficiency and four (8%) had insufficiency. Radiologic bone abnormalities were observed in 22 (43%) cases; specifically, rickets in 16 (31%). No association was observed with vitamin D levels and liver disease severity (OR 1.27, 95% CI 0.12-13.31) nor with rickets score (OR 0.07, 95% CI 0.004-1.37).</p><p style="text-align: justify;"><strong>Conclusion:</strong> Majority of the children with cholestasis had vitamin D deficiency, with a third having radiographic findings of rickets. Serum vitamin D levels were not associated with liver disease severity or with rickets score.</p><p style="text-align: justify;"><strong>Key Words:</strong> Vitamin D, rickets, cholestasis, bone disease, bone abnormalities</p>

Clinical Manifestation in Females with X-linked Metabolic Disorders: Genetic and Pathophysiological Considerations

Abstract Inborn errors of metabolism are predominantly autosomal-recessive disorders, but several follow an X-linked pattern of inheritance. They are called X-linked recessive, if the female carriers are asymptomatic, and are called X-linked dominant disorders, if almost all females are affected. Conditions, in which some females have symptoms while others are asymptomatic lifelong are simply referred to as X-linked. The aim of this review is to point out the variability in clinical manifestation of affected females in some X-linked metabolic disorders and to discuss on the basis of these examples possible mechanisms that may explain the broad phenotypic spectrum, such as the type of the underlying mutation, the issue of autonomous versus non-autonomous gene expression and the degree of skewing of X-inactivation. The use of the terms "X-linked dominant" and "X-linked recessive" will be discussed.

Vitamin D-dependent rickets (VDDR) type 1: case series of two siblings with a CYP27B1 mutation and review of the literature / Raquitismo dependente de vitamina D: tipo 1: série de casos de dois irmãos com mutação CYP27B1 e revisão da literatura

Abstract Two siblings presented with clinical and biochemical features of rickets, initially suspected as hypophosphatemic rickets. There was no improvement initially, hence the siblings were reinvestigated and later diagnosed as having vitamin D-dependent rickets (VDDR) type 1 due to a rare mutation in the CYP27B1 gene encoding the 1α-hydroxylase enzyme. Both siblings improved with calcitriol supplementation. The initial presentation of VDDR is often confusing and algorithmic evaluation helps in diagnosis. We also present a brief review of the literature, including genetics.

Resumo Dois irmãos apresentaram características clínicas e bioquímicas do raquitismo, com suspeita clínica inicial de raquitismo hipofosfatêmico. Não houve melhora no início, portanto os irmãos foram reavaliados e, posteriormente, diagnosticados com raquitismo dependente de vitamina D (VDDR) tipo 1 devido a uma rara mutação no gene CYP27B1, que codifica a enzima 1a-hidroxilase. Ambos os irmãos melhoraram com a suplementação de calcitriol. A apresentação inicial do VDDR geralmente é confusa e a avaliação algorítmica ajuda no diagnóstico. Também apresentamos uma breve revisão da literatura, incluindo genética.

Prevalence and clinical characteristics of X-linked hypophosphatemia in Paraná, southern Brazil

ABSTRACT Objective: The aim of this cross-sectional study was to estimate the prevalence of XLH in Paraná, a state in southern Brazil, and report the clinical features and complications of the disease. Materials and methods: We invited all endocrinologists (n = 205), nephrologists (n = 221), orthopedic surgeons (n = 1020), and pediatricians (n = 1000) in Paraná to fill out an electronic survey with information on patients with X-linked hypophosphatemia (XLH), and searched the records of the state's health department for all calcitriol prescriptions in 2018. Results: In all, 244 (10%) specialists responded to the email, of whom 18 (7.4%) reported to be taking care of patients with XLH and answered the online survey. A total of 57 patients with XLH were identified (prevalence 5 per million inhabitants). The median age at diagnosis was 22 years, and 42.2% were children and adolescents. Fifteen patients had genetic testing showing a PHEX mutation. Overall, 91.2% had bone deformities, 30.8% had a history of fragility fractures, and 22.4% had renal complications. Conclusion: This study demonstrated a prevalence of XLH of 5 cases per million inhabitants in the state of Paraná, a rate lower than the one reported in other countries. Manifestations of renal calcification and bone fragility were frequent among the patients. This is the first epidemiological study evaluating the prevalence and clinical presentation of XLH in Latin America.