Clinical phenotypes of spinal muscular atrophy patients with hybrid SMN gene

Background Spinal muscular atrophy (SMA) is a neuromuscular disease caused by homozygous deletion of SMN1 exons 7 and 8. However, exon 8 is retained in some cases, where SMN2 exon 7 recombines with SMN1 exon 8, forming a hybrid SMN gene. It remains unknown how the hybrid SMN gene contribute to the SMA phenotype. Method We analyzed 515 patients with clinical suspicion for SMA. SMN1 exons 7 and 8 deletion was detected by PCR followed by enzyme...