Spinal muscular atrophy in black South Africans: concordance with the universal SMN1 genotype.

Only one study has reported on the genetic basis of spinal muscular atrophy (SMA) in South African subjects. This was conducted in the Johannesburg region and has suggested that black South Africans only (indigenous Africans) differ from the norm. We have explored this further by DNA studies in 30 unrelated and racially diverse patients who reside in the Western Cape, and who were assessed as SMA subjects according to the internationally accepted inclusion criteria for SMA. These subjects were seen at the neurology clinic at Red Cross Children's Hospital in Cape Town during the period 1980-2001. Four had the type 1 form of SMA, 16 had type 2 and 10 had type 3. All patients were found to be homozygous for the loss of either exon 7 or exons 7 and 8 of the SMN1 gene. Six additional patients had anterior horn cell disease but were negative for the SMN1 gene deletion. All six had exclusion features listed in the international guidelines. This study shows that all patients from the Western Cape, which included 12 black South Africans, are no different genetically or phenotypically from the internationally recognized form of typical SMA.