Late onset dopa-responsive dystonia with tremor, gait freezing and behavioural disturbance and a normal dopamine transporter scan.

A 79-year-old woman presented with dystonic posturing of the right leg while walking and an action tremor of her hands, both of which were levodopa responsive. She subsequently developed gait freezing. However, there was neither generalised bradykinesia nor rigidity. Structural imaging showed no significant changes, and a dopamine transporter scan was normal. She subsequently required rapidly escalating doses of levodopa in order to achieve symptom control, raising concerns over the possible development of a dopamine dysregulation syndrome. Issues raised included the difficulties of managing patients with a rare diagnosis and the role of dopaminergic medication with the potential for abuse.