Contractures, continuous muscle discharges, and titubation

A mother and 2 children had abnormally fixed postures of the hands and feet at birth. At adolescence, intermittent attacks of shaking and titubation with dysarthria and, rarely, abnormal hand posturing developed in all 3. Electromyographically, there were continuous muscle discharges inhibited only by curare. Muscle biopsy in the younger child showed a distinct population of small fibers staining intensely with oxidative enzymes and myosin adenosine triphosphatase after acid preincubation. The mother's biopsy specimen contained similar cells, occasionally split or grouped. The electron microscopical findings were unremarkable. It appears likely that a single physiological abnormality underlies the abnormal central and peripheral nervous system discharges. A pool of low‐threshold neurons may account for the symptoms, with the abnormal discharge arising from the unusual muscle fibers seen on biopsy.