Acute onset spinal muscular atrophy in siblings.

We describe two sisters who each presented in infancy with acute, severe, generalised weakness and are-flexia in association with an intercurrent infection. The clinical picture resembled acute polyneuritis, but EMG findings and the later clinical features were consistent with a diagnosis of spinal muscular atrophy. Although symptoms in SMA may be exacerbated by infection, immunisation or trauma, this unusual presentation of the condition in siblings suggests that this may constitute a genetically distinct subgroup of the disorder.