[Phenotype-genotype correspondence in spinal muscular atrophy in a Moroccan family]

Spinal muscular atrophy (SMA) is an autosomal recessive disorder with a highly variable clinical course and prognosis. We report on the cases of three siblings with SMA. The weakness muscular observes at three siblings but more earlier and severe to the index case with a fast evolution towards respiratory distress syndrome resulting in its death at 5 years. The homozygous deletions of exons 7 and 8 of the telomeric SMN gene were found in all three siblings. No child showed deletion of NAIP gene. Muscular weakness and respiratory distress severity however were different among the siblings. The index patient died at the age of 5 because of respiratory insufficiency. Several molecular mechanisms may be involved in such phenotypic variability. The PCR-RFLP method allows to confirm clinical diagnosis of SMA in children, while avoiding more invasive methods such as EMG and muscular biopsy. However, this diagnostic tool does not allow yet the distinction between different clinical forms of SMA.