Objective: We present a young woman with myoclonic dystonia due to a novel mutation in SCL2A1 gene.

Background: Mutations in the SCL2A1 gene can cause non epileptic GLUT-1 deficiency with paroxysmal myoclonus-dystonia. Typically there are no seizures. It is associated with paroxysmal dyskinesias including intermittent ataxia, choreoathetosis, dystonia and alternating hemiplegia. It is triggered by exercise, anxiety and stress. DYT 18 (paroxysmal exercise induced dyskinesia and epilepsy) and DYT 9 (paroxysmal choreoathetosis and spasticity) have been reclassified under GLUT-1 deficiency. Treatment is usually with the ketogenic diet.

Methods: Case report.

Results: A 22 year old woman had a tremor from the age of 12. The tremor was constant but variable in severity and occurred at rest and on action. She also had intermittent jerks, affecting her left more than right arm, which were worse if she was tired, stressed or felt hot. She sustained a number of injuries due to the sudden jerks. She had also noticed nausea and tremulousness with exercise. There was no difference with fasting. She also had a history of migraine. She noticed some cramping of her hand with writing. Her father had episodic cramping and clawing of his right hand and died of colon cancer at 58. Relevant findings on examination included dystonic posturing of her right hand with dystonic spasms of her hand during writing, postural jerky tremor (right more than left), kinetic tremor (left more than right) and difficulty with tandem gait. MRI brain and DAT scan were normal. Genetic testing for DYT 1 and sarcoglycan epsilon were negative. Dystonia gene panel testing revealed a heterozygous mutation in exon 10 of the SCL2A1 gene (c. 1366A>G predicted to result in the p.Lys456Glu protein change) consistent with a diagnosis of paroxysmal exertion induced dyskinesia 2, however this patient has persistent symptoms which worsen intermittently.

Conclusions: This is a novel mutation and has not previously been reported in the literature. The increasing availability of next generation sequencing will expand the phenotype of many genetic conditions. We report a novel SCL2A1 mutation and expand the phenotype to include persistent but fluctuating myoclonic dystonia.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/persistent-myoclonic-dystonia-due-to-scl2a1-mutation/