Clinical and Genetic Study of Algerian Patients with Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is the second most common lethal autosomal recessive disorder. It is divided into the acute Werdnig-Hoffmann disease (type I), the intermediate form (type II), the Kugelberg-Welander disease (type III), and the adult form (type IV). The gene involved in all four forms ofSMA, the so-called survival motor neuron (SMN) gene, is duplicated, with a telomeric (telSMNorSMN1) and a centromeric copy (centSMNorSMN2).SMN1 is homozygously deleted in over 95% ofSMApatients. Another candidate gene inSMAis the neuronal apoptosis inhibitory protein (NAIP) gene; it shows homozygous deletions in 45–67% of type I and 20–42% of type II/type III patients. Here we studied theSMNandNAIPgenes in 92 AlgerianSMApatients (20 type I, 16 type II, 53 type III, and 3 type IV) from 57 unrelated families, using a semiquantitative PCR approach. Homozygous deletions ofSMN1 exons 7 and/or 8 were found in 75% of the families. Deletions of exon 4 and/or 5 of theNAIPgene were found in around 25%. Conversely, the quantitative analysis ofSMN2 copies showed a significant correlation betweenSMN2 copy number and the type ofSMA.