An unusual form of metachromatic leukodystrophy in three siblings.

An unusual form of Metachromatic Leukodystrophy (MLD) has been described in three siblings who are the sole children of related parents of Iranian origin. Clinical progression in the three siblings was insidious and protracted, the hallmark of the condition being a dystonia mainly induced by intention and manifested by dysarthria and torsion spasm of the neck, spine and extremities. The dysarthria sometimes culminated in apparent choreoathetosis. Laboratory studies included positive sural nerve biopsies, prolonged nerve conduction times and a marked deficiency of arylsulfatase A in the urine, leukocytes and fibroblasts. The parents presented no clinical manifestations, but the arylsulfatase A activity in both was reduced by 50%.