CAPOS Syndrome with Fluctuating Symptoms

We report a patient with CAPOS syndrome (Cerebellar ataxia, Areflexia, Pes cavus, Optic atrophy, and Sensorineural hearing loss) with classic features who also exhibited fluctuating vestibulocochlear symptoms that met the criteria for Meniere’s disease. A male patient was initially symptomatic at 13 months of age with ataxia and loss of deep tendon reflexes in the setting of fever. This was followed by the development of baseline ataxia with superimposed spells of vertigo and ataxia, progressive hearing loss with episodic fluctuations, optic atrophy, pes cavus, and areflexia. Spells lasted minutes to hours and were frequently triggered by ambient heat and fever. He was diagnosed with a de novo pathogenic variant p.Glu818Lys mutation in ATP1A3. We provide detailed clinical features of this case, a summary of CAPOS cases reported to date, and an overview of allelically related syndromes.