From enigmatic to problematic

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Abstract
The genetics of SMA has been stunningly complex. Two groups of researchers looking for the SMA gene have reported evidence that supports unrelated but neighboring candidate genes, either of which, if discovered by itself, would have been hailed as a strong candidate. Each fulfills the criterion that has been useful in identifying candidate genes for other disorders: the close association between disabling mutations of the gene and the disease. But each of these reports harbors inconsistencies that require unconventional explanations to preserve the candidacy status of their gene--a suspension of disbelief that most investigators would be willing to grant were it not for the other group's findings. Some of the confusion surrounding the molecular genetics of SMA is no doubt due to our present incomplete understanding, but the very complexity of the SMA-containing region of chromosome 5 itself is responsible for many of the pathogenic mutations. Genetic complexity is thus at once the reason for our present confusion, the spur for further research, and a major cause of the disease.