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.