Further characterization of CAPOS/CAOS syndrome with the Glu818Lys mutation in the ATP1A3 gene: A case report.

A 38-year-old female patient experienced recurrent episodes of neurological deterioration during febrile illness at the age of 7 and 8 months, and 2, 4, and 37 years. Acute symptoms comprised unconsciousness, headache, abnormal ocular movements, flaccid paralysis with areflexia, ataxia, dysphagia, and movement disorders. Each episode of neurological deterioration was followed by partial recovery with residual symptoms of progressive disturbance of visual acuity with optic atrophy and hearing loss, moderate intellectual disability, strabismus, ophthalmoplegia, as well as fluctuating degree of gait ataxia, chorea, tremor, and myoclonus. In addition, electrocardiography revealed incomplete right bundle branch block. The genetic testing revealed a de novo heterozygous mutation of c.2452G > A (p.Glu818Lys) in the ATP1A3 gene, which was compatible with the clinical phenotype of CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss)/CAOS syndrome. Here we discuss the significance of clinical features of a patient, overlapping with those of alternating hemiplegia of childhood, along with a literature review.