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December 1985

Hexosaminidase-A Deficiency Presenting as Atypical Juvenile-onset Spinal Muscular Atrophy

Author Affiliations

From the Department of Neurology and Neurosurgery, McGill University, Montreal, and the Montreal Neurological Institute (Drs Parnes, Karpati, Carpenter, Kin, and Wolfe); Dr Suranyi is in private in Cornwall, Ontario, Canada.

Arch Neurol. 1985;42(12):1176-1180. doi:10.1001/archneur.1985.04060110058016

• Three patients from two families had an unusual phenotypical variant of late-onset hexosaminidase-A deficiency. The clinical picture was dominated by spinal motor neuron involvement mimicking juvenile-onset spinal muscular atrophy. Atypical features included prominent muscle cramps, postural and action tremor, recurrent psychosis, incoordination, corticospinal and corticobulbar involvement, and dysarthria. The presence of these atypical features in patients whose lower motor neuron involvement would otherwise be consistent with juvenileonset spinal muscular atrophy should raise the suspicion of the presence of hexosaminidase-A deficiency and GM2 gangliosidosis that can be proved by appropriate enzyme assays.