[Frequency of 5q spinal muscular atrophy in adults with unspecified neuromuscular diseases]

To assess the prevalence of 5q spinal muscular atrophy (SMA) among adult patients with undifferentiated neuromuscular disorders.

Prospective study of 50 patients (19-78 years) presenting ≥1 feature of 5q SMA: areflexia, proximal weakness, fasciculations, neurogenic EMG changes, atrophy, calf hypertrophy, or elevated creatine kinase (CK). Molecular testing (MLPA/melting curve analysis of SMN1/SMN2) was performed.

5q SMA was confirmed in one female patient (2% [95% CI 0.05-10.6]), who was found to have a homozygous deletion of exons 7-8 in the SMN1 gene. Her clinical presentation included proximal lower limb weakness and neurogenic EMG changes, but she lacked areflexia and had normal CK levels. For 29 years, she had been misdiagnosed with «unspecified myopathy»(G72.9).

The findings highlight the need to include 5q SMA in the differential diagnosis of adult patients with undifferentiated neuromuscular disorders. Optimizing diagnostic algorithms and enhancing epidemiological monitoring in this age group are essential to reduce diagnostic delays.