Lisdexamfetamine Therapy in Paroxysmal Non‐kinesigenic Dyskinesia Associated with the KCNMA1‐N999S Variant

BACKGROUND: KCNMA1‐linked channelopathy is a rare movement disorder first reported in 2005. Paroxysmal non‐kinesigenic dyskinesia (PNKD) in KCNMA1‐linked channelopathy is the most common symptom in patients harboring the KCNMA1‐N999S mutation. PNKD episodes occur up to hundreds of times daily with significant morbidity and limited treatment options, often in the context of epilepsy. CASES: We report 6 cases with the KCNMA1‐N999S variant treated with lisdexamfetamine (0.7–1.25 mg/kg/day), a pro‐drug of dextroamphetamine. Data were collected retrospectively from interviews and chart review. Parent‐reported daily PNKD episode counts were reduced under treatment, ranging from a 10‐fold decrease to complete resolution. CONCLUSION: Our findings suggest that lisdexamfetamine is an effective therapy for PNKD3 (KCNMA1‐associated PNKD). Treatment produced dramatic reductions in debilitating dyskinesia episodes, without provocation or exacerbation of other KCNMA1‐associated symptoms such as seizures.