What is the definition of CAPOS Syndrome?
Cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS) syndrome is a neurological disorder. The syndrome gets its name from the different parts of the body it usually affects:
- Cerebellar ataxia: inflammation of the cerebellum, the part of the brain that helps control the coordination of muscle movement
- Areflexia: loss of reflexes
- Pes cavus: high arch in foot
- Optic atrophy: damage to the optic nerve of the eye
- Sensorinural hearing loss: damage to the nerves involved in hearing
CAPOS syndrome typically begins after a fever-related illness with a sudden episode of ataxia, such as having a hard time walking or coordinating leg or arm movements. The ataxia is usually associated with generalized weakness and/or inflammation of the brain (encephalopathy). The first episode most often happens between the ages of 6 months and 5 years. Pregnancy and delivery may also trigger episodes. Most people with CAPOS syndrome have one to three episodes during their lifetime. Other signs and symptoms during an episode may include low muscle tone, unusual eye movements (nystagmus or strabismus), problems with speech (dysarthria), difficulty swallowing (dysphagia), reduced or absent reflexes, and hearing loss. Some people may lose consciousness or go into a coma during an episode. Though many of the signs and symptoms of CAPOS syndrome get better as the fever and illness improve, some symptoms, including movement problems, may continue. Vision changes (optic atrophy) and sensorineural hearing loss tend to worsen over time, although the severity and rate of progression varies. Long-term management may include physical therapy, hearing and vision aids, and regular exams to check for changes in vision, hearing, and muscle coordination.
What are the alternative names for CAPOS Syndrome?
- CAPOS syndrome
- Cerebellar ataxia - areflexia - pes cavus - optic atrophy - sensorineural hearing loss
- Cerebellar ataxia-areflexia-pes cavus-optic atrophy-sensorineural hearing loss syndrome
What are the causes for CAPOS Syndrome?
CAPOS syndrome is caused by specific changes (mutations) in the ATP1A3 gene. These changes can be inherited in an autosomal dominant manner or may happen by mistake during the formation of the egg or the sperm (de novo). Diagnosis is usually suspected based on symptoms and the results of a brain MRI and muscle and nerve tests (EMG evaluations). Testing to evaluate changes in the optic nerve and nerves involved in hearing may offer additional support. The diagnosis of CAPOS syndrome is confirmed by genetic testing.
Other syndromes that may also be caused by different changes or mutations in the ATP1A3 gene include rapid-onset dystonia-parkinsonism (RDP) and alternating hemiplegia of childhood (AHC). In some cases the signs and symptoms of these syndromes may overlap.