Proximal spinal muscular atrophy (SMA) is a common fatal autosomal recessive disorder caused by deletion or mutation of the survival of motor neuron 1 (SMN1). Here, the authors studied SMA molecular pathology in 653 Chinese patients and found approximately 88.2% with homozygous SMN1 exon 7 deletion and 6.3% with heterozygous exon 7 loss using multiplex ligation-dependent probe amplification. SMN1 variants were detected in 34 patients with heterozygous SMN1 loss by clone sequencing. In 27 of them, 15 variants were identified, five of which were unreported novel variants. This study could facilitate early diagnosis for SMA patients in mutation detection and revealed the specific mutation spectrum of SMN1 in Chinese SMA and high genetic heterogeneity in subtle variants observed between patients from China and Caucasians.
