Objective: Present a novel case of PRRT2 positive PKD presenting with paroxysmal dystonia that responded to treatment with carbidopa levodopa. First report in the literature.

Background: Paroxysmal Kinesigenic Dyskinesia (PKD) is an autosomal dominantly inherited movement disorder classically characterized by dyskinesia with recurrent attacks of brief involuntary movement triggered by initiation of voluntary movement. Treatment with carbamazepine has been found to decrease symptoms. Diagnosis of PKD can be supported by genetic testing that demonstrates a pathogenic variant of the PRRT2 gene.  To our knowledge, levodopa has not been used in prior published studies.

Method: A retrospective review of the patient’s clinical presentation, diagnostic workup, and treatment response was conducted and compared with findings from a literature review of PRRT2 positive PKD cases.

Results: A 33-year-old active-duty service member who presented with an episode of dystonia with involuntary muscle spasms of the left hemi-body following administration of prochlorperazine for migraines earlier that day. Prior history includes episodes of transient lower extremity ankle forced flexion that resolved in 20 seconds to 5 minutes with rubbing his calf. Dystonic symptoms improved in the emergency department with diazepam and methocarbamol. Patient followed up with neurology two months later where he reported a history of facial and lower extremity muscle spasms lasting 1-3 seconds, resolving with rest, and had a neurological exam with increased left ankle tension and difficulty with finger tap. EEG and Brain MRI were unremarkable. Genetic testing confirmed a heterozygous PRRT2 variant. Carbidopa levodopa was started before genetic results obtained given the patients history of dystonic symptoms. In follow up appointments, patient reported positive symptom response to carbidopa levodopa with no recurrence of dystonic or dyskinetic movements.

Conclusion: PRRT2 PKD is classically treated with carbamazepine. In this novel case, a patient with PKD developed overt hemi-dystonia after treatment with prochlorperazine. This is a novel presentation and is postulated to have unmasked episodic dystonic symptoms. Given his history of dystonia, treatment with carbidopa-levodopa was started and dyskinesia resolved, suggesting the ability to use carbidopa-levodopa as a treatment in  specific phenotypes of PKD.

References: Landolfi A, Barone P, Erro R. The Spectrum of PRRT2-Associated Disorders: Update on Clinical Features and Pathophysiology. Front Neurol. 2021 Mar 4;12:629747. doi: 10.3389/fneur.2021.629747. PMID: 33746883; PMCID: PMC7969989.

Yang K, Quiroz V, Ebrahimi-Fakhari D. PRRT2-Related Disorder. 2018 Jan 11 [Updated 2024 Jul 4]. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2025. Available from: https://www.ncbi.nlm.nih.gov/books/NBK475803/

Disclaimer:
1. “The views expressed herein are those of the author(s) and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the U.S. Government.”

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MDS Abstracts - https://www.mdsabstracts.org/abstract/novel-presentation-of-prrt2-with-paroxysmal-dystonia-and-responsive-to-carbidopa-levodopa/