Objective: To describe an unusual co-occurrence of disorders involving dopaminergic dysregulation.

Background: TD and RLS result from opposing abnormalities in dopaminergic transmission pathways in the brain. We present a case of comorbid TD and RLS, highlighting management challenges and reviewing their interacting pathophysiology.

Method: A 51-year-old woman with depression treated with aripiprazole and duloxetine for 7 years and family history of RLS presented with involuntary movements. 3 years prior, she had developed an urge to move her legs at night relieved by walking, diagnosed as RLS. Neither low ferritin repletion nor a brief trial of ropinirole were helpful symptomatically. Several months after onset of her leg movements, she developed involuntary oral movements. Due to concern for TD, aripiprazole was stopped abruptly and she was started on valbenazine. There were mild changes in her oral movements but her RLS worsened especially with uptitration of valbenazine.

Results: At our initial visit, exam was notable for intermittent mild puckering and smacking of the lips consistent with TD. Brain MRI, TSH, ceruloplasmin, and electrolytes were normal. She was started on gabapentin to treat RLS which led to modest improvement. We discontinued her valbenazine, and she reported more mouth movements and extra movements in the legs without urgency or discomfort, which felt distinct from her typical RLS. Gabapentin was uptitrated and she was started on deutetrabenazine (later switched to tetrabenazine due to worsening depression) for the TD. On her current regimen of tetrabenazine 12.5 mg twice daily and gabapentin 600 mg three times daily, her involuntary movements have improved and RLS is well-controlled.

Conclusion: To our knowledge, this is the first case report of comorbid TD and RLS. Reduced dopaminergic signaling is implicated in RLS. TD is thought to arise from dopamine hypersensitivity in the nigrostriatal pathway due to long-term neuroleptic use. In this case, RLS arose in the setting of chronic dopamine blockade, low iron stores, and likely genetic susceptibility. With dopamine depletion using a VMAT2 inhibitor, our patient experienced worsening of RLS. Downtitration of this agent was associated with involuntary oral and leg movements different from typical RLS symptoms, concerning for TD in the limbs. Treatment required a delicate balance of dopamine blockade for TD while avoiding dopamine depletion that would worsen RLS.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/comorbid-tardive-dyskinesia-td-and-restless-leg-syndrome-rls/