Differential Diagnosis between Duchenne Muscular Dystrophy and Limb Girdle Muscular Dystrophy 2a.

Abstract

Limb Girdle Muscular Dystrophy 2A (LGMD 2A) is the most common form of limb girdle muscular dystrophies caused by mutations in the calpain-3 gene (CAPN-3). The pattern of LGMD 2A can be clinically indistinguishable from that of Duchenne Muscular Dystrophy (DMD). We report a case of a 14-year-old boy which has the initial diagnosed as DMD at 6 years old, based on clinical features and very elevated serum creatine kinase levels. A muscle biopsy at the age of 10 showed atypical features which suggested a histiocytosis or neural damage. An MRI conducted 2 years later revealed fatty degeneration predominantly in the posterior region of the thigh and led the diagnosis to LGMD 2A, as well as the necessity to repeat the biopsy. Immunohistochemical analysis was normal for dystrophin, but the Western Blott showed a normal/borderline amount of calpain-3 in the muscle. We also performed a molecular analysis that identified a compound heterozygous mutation of the calpain 3 gene (CAPN 3). LGMD 2A was often misdiagnosed as DMD due to the similarities in clinical manifestations and technique limitations; the immunohistochemical examination, the magnetic resonance imaging examination and the molecular analysis are an essential tool for establishing a right diagnosis.