A New Familial Syndrome with Dystonia and Lower Limb Action Myoclonus

Background: Myoclonus-dystonia (M-D) is genetic and clinically heterogeneous. Identification and description of rare M-D syndromes may contribute to gene identification. Results: Here, we describe a new, autosomal dominant M-D syndrome in a 3-generation pedigree showing anticipation. Patients have progressive action-induced multifocal dystonia and generalized myoclonus. A remarkable feature of the syndrome is action myoclonus in the lower extremities triggered by upright posture, causing instability. Electrophysiological characterization shows a 12-Hz peak in the EMG autospectrum and corticomuscular and intermuscular coherences. Conclusions: A new familial M-D syndrome with progressive action myoclonus and dystonia is described. (C) 2011 Movement Disorder Society