[PS17-3A-3 ] Dystrophinopathy and differential diagnoses in Iran
Duchenne (DMD) and Becker muscular dystrophies are the most frequent neuromuscular diseases in children and caused by mutations in dystrophin gene. Multiplex ligation-dependent probe amplification (MLPA) is the initial diagnostic test of choice. Muscle biopsy is recommended for Duchenne phenotype patients with negative genetic study. Immunohistochemistry is essential to show loss of dystrophin expression. The majority of dystrophin-positive children presenting with Duchenne-like phenotype are suffering from sarcoglycanopathy in Iran. The sarcoglycanopathies are a family of autosomal-recessive limb-girdle muscular dystrophy (LGMD). The phenotype varies from Duchenne-like to milder forms. The most common type of Sarcoglycanopathy in Iran is beta sarcoglycanopathy followed by gamma sarcoglycanopathy, this is different from what has been reported from other countries. The other LGMDs with duchenne-like or Becker-like phenotypes are Calpainopathy (LGMD 2A) and LGMD type 2I. The clinical picture in the juvenile onset cases of acid maltase deficiency is variable. Some cases may present with respiratory failure, and some may resemble Becker or limb-girdle muscular dystrophy. Spinal muscular atrophy (SMA) type III is the mildest form of SMA in which onset is later and ambulation is achieved. Weakness is mainly confined to the proximal muscles of the lower limbs and clinically it is very similar to a LGMD. Lipid storage disease with myopathy may present in childhood or adolescence as slowly progressive muscle weakness. Muscle weakness in juvenile dermatomyositis may be proximal and symmetrical, as in DMD or LGMDs. Occasionally patients have no pain or skin rash and only muscle biopsy leads to a correct diagnosis.