[Dopa-responsive dystonia--a hereditary dystonia easy to treat]

Dopa-responsive dystonia is a genetically determined disorder with early onset. The dystonia usually manifests as a disturbance of gait with fatigue and may be confused with spasticity. The diagnosis is based on clinical recognition and response to l-dopa, which is usually complete and long lasting. The most common genetic defect involves the gene for GTP cyclohydroxylase I.

We describe a Norwegian family in which three generations are affected.

All those affected had gait disturbance from childhood; the disturbance became worse during the day and after exercise. Clinical examination revealed reduced fine motor skills and brisk tendon reflexes. Dystonic posturing of one or both legs could be seen during walking. All patients were treated with l-dopa with excellent effect.

Though uncommon, this disorder is an important differential diagnosis in children with gait disturbance, particularly in those suspected as having spastic paraparesis.