Limb-Girdle muscular dystrophy in Brazilian children: clinical, histological and molecular characterization

Introdução: As distrofias de cinturas representam um grupo de miopatias progressivas, geneticamente determinadas, envolvendo 16 formas de herança autossômica recessiva e oito dominantes, sendo as formas recessivas mais comuns, particularmente em crianças. Caracterizam-se por fraqueza muscular progressiva de predomínio proximal em cinturas escapular e pélvica, existindo desde formas graves de início na infância a formas leves de início em adultos. A biópsia muscular, com estudo histológico e imunoistoquímico, é fundamental para o diagnóstico, porém o exame molecular é o teste padrão ouro para o diagnóstico de certeza. Objetivos: Determinar a freqüência dos diferentes subtipos de distrofia de cinturas em crianças na nossa população, descrevendo os aspectos clínicos, histológicos e moleculares. Resultados: Fizeram parte deste estudo 39 crianças provenientes do ambulatório de doenças neuromusculares do HC-FMUSP, sendo a proporção entre o sexo feminino e masculino de 3:1. A idade de início da doença variou de dois a 13 anos, com média de 7,5 anos. Os sinais e sintomas na apresentação clínica incluíram: quedas frequentes (22 casos), dificuldades em subir escadas (13 casos), marcha digitigrada (2 casos) e dificuldades para se levantar do chão (2 casos). Os níveis de CK foram elevados em todos os pacientes, sendo maiores naqueles com diferlinopatia e algumas formas de sarcoglicanopatias. Dentre os 39 pacientes, 37 foram classificados como LGMD. Destes, 15 (40,5%) receberam o diagnóstico de sarcoglicanopatia (LGMD2C-F), cinco (13,5%) de disferlinopatia (LGMD2B), cinco (13,5%) de calpainopatia, dois (5,5%) de LGMD1B, dois (5,5%) de LGMD2I, um (2,5%) de caveolinopatia (LGMD1A), e em sete (19%) não foi possível identificar o subtipo específico. A biópsia muscular mostrou um padrão distrófico em todos os casos, sendo mais acentuado nas sarcoglicanopatias e na LGMD2I. A presença de inflamação foi incomum na LGMD2B, e a presença de fibras lobuladas foi um achado marcante na LGMD2A. Conclusões: O diagnóstico do subtipo específico de LGMD em crianças é um desafio. Este estudo em crianças brasileiras provenientes de um centro de doenças neuromusculares de um grande hospital da rede pública mostrou alta frequência de sarcoglicanopatias, seguida por LGMD2A e LGMD2B. Já a LGMD2I parece ser incomum no BrasilBackground: Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of genetic muscular dystrophies, involving 16 autosomal recessive subtypes and eight autosomal dominant subtypes. Autosomal recessive dystrophy is far more common than autosomal dominant dystrophy, particularly in children. The clinical course in this group is characterized by progressive proximal weakness, initially in pelvic and after in shoulder-girdle musculature, varying from very mild to severe degree. Significant overlap of clinical phenotypes, with genetic and clinical heterogeneity, constitutes the rule for this group of diseases. Muscle biopsies are useful for histopathologic and immunolabeling studies, and DNA analysis is the gold standard to establish the specific form of muscular dystrophy. Objectives: The aim of this study was to characterize the clinical, histological and molecular aspects in children with LGMD who attend a big public neuromuscular centre in our country to determine the frequency of different forms. Results: Thirty seven patients were classified as LGMD and included in this analysis. The study period extended from 2009-2012. The female to male ratio was 3:1. The age of onset ranged from two to 13 years, mean 7,5 years. Onset in the first decade was seen in 90%. The initial clinical signs included: frequent falls (22 cases), difficulty in climbing stairs (13 cases), walk on tip toes (2 cases), difficulty in rising from the floor (2 cases) and difficulty on walking (1 case). The serum CK levels were high in all cases. Among the 37 patients, 15 (40,5%) were classified as sarcoglycanopathies (LGMD2C-F), five (13,5%) as dysferlinopathy (LGMD2B), five (13,5%) as calpainopathy (LGMD2A). Mutations in LMNA gene (LGMD1B), FKRP gene (LGMDI) and caveolin gene (LGMD 1C) were identified in two (5,5%), two (5,5%) and one patient (2,5%), respectively. In seven of 37 cases (19%) it was impossible to determine specific diagnosis. Calf hypertrophy, scapular winging and scoliosis were the most characteristic signs in sarcoglycanopathies. In LGMD2I calf hypertrophy is also observed. Atrophy of posterior compartment of thighs is frequent in children with LGMD2B and could suggest the diagnosis. In LGMD2A winging of scapulae and contractures in Achilles tendons were important findings. Muscle biopsy showed a dystrophic pattern in all cases, more intense in sarcoglycanopathies and LGMD2I. Differently from adult\'s patients, inflammation changes in dysferlinopaties were uncommon. Lobuled fibers were characteristic changes in calpainopathies in children. Conclusions: A definitive diagnosis among various subtypes of LGMD in children is challenging. Our series was a large study on LGMD in Brazilian children and showed high frequency of sarcoglycanopathies followed by LGMD2A, LGMD2B, LGMD2I, LGMD1B and LGMD1