Spinal muscular atrophy Sample Clauses

Spinal muscular atrophy. The childhood spinal muscular atrophies (SMA) share many features in common with ALS, and linkage to an area of chromosome 5q13 has now been shown. This is an extremely difficult area to analyse as there are inverted duplications and pseudogenes. There is no consensus map of the order of genes and markers in this region, but the 2 common interpretations are shown above and below the diagram (Figure 1-1) respectively. Two groups published results of mutation studies of 2 genes within this region simultaneously. Deletions of exons 7 and 8 of the telomeric copy of the survival motor neuron (SMN) gene were found in more than 98% of cases, with point mutations in the remainder but homozygous deletions were found in some controls (Xxxxxxxx et al. 1995). Conversely, deletions of exons 5 and 6 of the telomeric copy of neuronal apoptosis inhibitory protein (NAIP) were found in 45% of type 1 SMA, and in 18% of types 2 and 3. They were also found in 2% of carriers but in none of more than 1400 controls (Xxx et al. 1995). In other words, all patients with SMA have deletions or point mutations of SMN(tel) and all those with deletions of NAIP(tel) have SMA or are carriers. A study of SMN and NAIP deletions in 154 patients with ALS, of whom 18 had pure lower motor neuron features, found none with SMN deletions and one with homozygous deletion of NAIP exon 5 (Xxxxxxx et al. 1996). The patient had El Escorial definite ALS, onset aged 63 and died 2 years later. His features were those of typical ALS with upper and lower motor neuron signs and no added findings such as sensory signs or dementing illness. Deletions responsible for SMA are therefore unlikely to be important factors in the pathogenesis of ALS. 7,8 SMN NAIP NAIP SMN NAIP SMN SMN NAIP Figure 1-1. Chromosome 5q13 genes.