Application of DNA-based tests for diagnosis of spinal muscular atrophy in Saudi Arabia.

We examined the deletion of the survival motor neuron (SMN) and neuronal apoptosis inhibitory protein (NAIP) genes in patients with spinal muscular atrophy (SMA) using polymerase chain reaction followed by restriction site assay methods. The study included 16 Saudi patients (9 SMA type I and 7 SMA type II) and 6 healthy Saudi volunteers. The homozygous deletions of exons 7 and 8 of the telomeric SMN gene, and exon 5 of the NAIP gene were found in all SMA type I patients. Exons 7 and 8 of telomeric SMN were deleted in all SMA type II patients. However, exon 5 of NAIP was deleted in three of the seven cases. All control volunteers and all family members of the patients had normal SMN and NAIP. The incidence of NAIP deletion was higher in the more severe SMA cases and the dual deletion of the SMN and NAIP genes was more common in Saudi SMA type I patients compared with patients of other ethnic groups.