Dopamine dysregulation syndrome in a patient with restless legs syndrome

A middle-aged architect, suffering from familial, idiopathic, levodopa-responsive restless legs syndrome (RLS) progressively abused levodopa for 10 years, to the point of taking 20 tablets/day (4000 mg/day) for 6 months. Such abuse (possibly linked to the rewarding effect of dopamine) has been recently monitored in the context of Parkinson's disease (PD) (the "dopamine dysregulation syndrome"). Physicians who now routinely treat RLS patients with dopaminergic agents should be aware of this abuse potential. This case also constitutes an experimental model. As levodopa abuse has only been described in patients with PD, it was suspected to be promoted by central dopamine depletion (with consequent sensitization of dopamine receptors). This idea should be revised because functional imaging showed that this RLS patient had no dopamine depletion. Later, he had no impulse disorders (no gambling, hypersexuality, excessive shopping), which occur with dopamine agonists, suggesting that levodopa abuse and impulse disorders can result through different mechanisms.