[Genotypic and clinical features of spinal muscular atrophy type 3]

To explore the genotypic and clinical features and laboratory examinations of spinal muscular atrophy type 3 (SMA III).

Results of genetic testing and laboratory exams of 18 SMA III patients were collected and analyzed.

The average age of onset of patients was 6.1 years, with the course of disease lasting from 13 months to 28 years. All patients became symptomatic with lower extremity muscle weakness. The symptoms gradually aggregated, with proximal lower limb muscle becoming atrophic and proximal upper limb muscle becoming weak. Genetic testing indicated that all subjects possessed homozygous deletions of SMN1 gene. Electromyography (EMG) of 15 subjects indicated neurogenic damage. Whilst younger patients had normal level of creatine kinase (CK), elder patients had higher level of CK, though no linear correlation was found.

Full understanding of Clinical, especially the growth features of SMA III, in combination with genetic testing, can facilitate diagnosis and early intervention of the disease.