ABSTRACT
Spinal muscular atrophy (SMA) is a neuromuscular disorder characterized by progressive anterior horn cell degeneration leading to motor weakness, muscular atrophy and denervation. Recently, the genes responsible for proximal muscular atrophy have been identified and named as survivor motor neuron (SMN) and neuronal apoptosis inhibitory protein genes. The clinical symptoms, courses and evaluation findings of proximal SMA type III are similar to those of distal SMA and proximal muscle myopathies such as limb gir-dle muscular dystrophy and fascioscapulohumeral muscular dystrophy. It cannot be diagnosed with muscle biopsy and electromyographic findings exclusively. In our case, the patient showed similar clinical manifestations of distal SMA. So we couldn't diagnose this case as SMA type III until we detected SMN 1 gene deletion. This case could be a good model for diagnostic approach to SMA type III and differential diagnosis to similar diseases.