Early onset dystonia decreasing with development. Case report of two children with familial myoclonic dystonia.

Two related girls had the onset of unilateral leg dystonia in the neonatal period and at 13 months, respectively. The dystonic signs subsided with motor development and resolved completely in one of the girls by the age of 5 years. There was no response to L-dopa. From 2-3 years of age segmental myoclonus with a shoulder girdle distribution appeared. Family investigation results were compatible with autosomal dominant myoclonic dystonia responsive to alcohol. The onset and resolution of dystonia have not been described previously. This disorder is genetically separate from torsion dystonia. No linkage has been found to the dopamine beta-hydroxylase gene locus. Genetically determined disorders of neurotransmission may add to our knowledge of the normal development of motor control and thus merit further study.