Hexosaminidase-A deficiency presenting as atypical juvenile-onset spinal muscular atrophy
S. Parnes, G. Karpati, S. Carpenter, N. M. Kin, L. S. Wolfe and L. Suranyi
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 juvenile-onset 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.
