Objective: To report a case of KCNA2 mutation variant with tics.

Background: Mutations in the KCNA2 gene impact the function of a voltage-gated potassium channel and may cause a spectrum of epileptic encephalopathies with additional clinical features.  Most often, symptoms present during infancy or childhood with epilepsy, developmental delay, hypotonia, ataxia, speech difficulty, and cerebral atrophy seen on MRI. Pathologic variants can cause a wide spectrum of autosomal dominant neurological phenotypes. Tremors and myoclonus have been reported in some cases. To our knowledge, tics have not been reported in this disorder.

Method: Case report and review of literature.

Results: We present the case of a 9-year-old female with developmental delay, hypotonia, and Lennox-Gastaut syndrome who presented to the movement disorder clinic for a wide range of motor and vocal tics. She had an uncomplicated birth, but seizure onset at 6 months, and severe delay of speech and motor milestones. She began having blinking, eye deviation, and hand shaking around age 4yo. Over time, she added arrhythmic facial contractions, humming, and compulsively touching the elbow. She had more complex sequences including chin protrusion-head nodding-body shivering, and stirring movements of the arms followed by throwing back the flexed forearms in rapid succession. She also experienced significant irregular, jerky tremors of the limbs that interfered with activities. She had severe spastic dysarthria as well as vocal tremor. She had a wide-based, spastic and ataxic gait with marked anteropulsion. (Video is presented). Behaviorally, she had compulsive tendencies of lining up all of her stuffed animals in a particular way and demanding that game sequences repeat the same pattern as the last time played. Work-up included an MRI with cerebellar, especially vermal atrophy. Chromosomal microarray, fragile X testing, and epilepsy gene panel were negative. Whole exome sequencing found her to be heterozygote for KCNA2 mutation (autosomal dominant), R297Q variant with specific mutation c.890G>A.

Conclusion: KCNA2 mutation variants can have wide phenotypic spectrum with seizures, developmental delay, and movement disorder features. Some cases have reported OCD and ADHD, but our case demonstrates that tics may be a newly recognized feature of the spectrum. The reported cases in the literature will be summarized in table form.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/expanding-the-phenotype-of-kcna2-mutation-tics-and-stereotypies/