Cerebellar ataxia-areflexia-pes cavus-optic atrophy-sensorineural hearing loss syndrome

Cerebellar ataxia-areflexia-pes cavus-optic atrophy-sensorineural hearing loss syndrome (also known as CAPOS syndrome) is a rare neurological disorder characterized by episodes of ataxia (impaired coordination and balance due to cerebellar dysfunction) triggered by febrile illness, typically beginning in early childhood. The syndrome is caused by mutations in the ATP1A3 gene, which encodes the alpha-3 subunit of the sodium-potassium ATPase pump, a critical enzyme for neuronal function. The acronym CAPOS stands for its cardinal features: Cerebellar ataxia, Areflexia (absence of reflexes), Pes cavus (high-arched feet), Optic atrophy (degeneration of the optic nerve leading to visual impairment), and Sensorineural hearing loss. The condition primarily affects the nervous system, including the cerebellum, peripheral nerves, auditory system, and optic nerves. During febrile episodes, patients typically experience acute onset of ataxia and hypotonia, which may partially resolve between episodes but often leaves progressive residual neurological deficits. Over time, patients may develop progressive sensorineural hearing loss and optic atrophy, leading to significant sensory impairment. Areflexia and pes cavus reflect peripheral nerve involvement. The severity and progression of symptoms can vary among affected individuals. There is currently no cure or disease-specific treatment for CAPOS syndrome. Management is supportive and multidisciplinary, focusing on physical therapy and rehabilitation for motor difficulties, hearing aids or cochlear implants for hearing loss, low-vision aids for optic atrophy, and orthopedic interventions for pes cavus. Prompt management of febrile illnesses may help reduce the severity of acute ataxic episodes. Genetic counseling is recommended for affected families.

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