Stiff man-like syndrome and generalized myokymia in spinocerebellar ataxia type 3

We describe the novel association of spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) phenotype combining classical clinical presentation and semeiology mimicking stiff man syndrome (SMS). The studied pedigree comprises seven affected members in three generations. Their clinical picture consisted of cerebellar ataxia, pyramidal signs, facial myokymia, and ophthalmoplegia. The proband was a 39-year-old man in whom such a clinical picture, 5 years after onset at age 29, evolved to severe SMS and widespread myokymia. Electrophysiological study revealed continuous muscle activity in proximal limb muscles. Molecular study demonstrated the MJD gene mutation in all four examined patients with 73 to 76 CAG repeats in the expanded allele. We conclude that an excess of motor unit activity including stiff man-like syndrome and widespread myokymia may be an integral part of the SCA3 clinical spectrum.