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Disease Profile

Cerebellar ataxia, areflexia, pes cavus, optic atrophy and sensorinural hearing loss

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

<1 / 1 000 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

CAPOS; CAPOS syndrome; Cerebellar ataxia areflexia pes cavus optic atrophy sensorineural hearing loss;


Congenital and Genetic Diseases; Ear, Nose, and Throat Diseases; Eye diseases;


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:[1][2][3]

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.[1][2] Pregnancy and delivery may also trigger episodes.[3] Most people with CAPOS syndrome have one to three episodes during their lifetime.[2] 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.[1][2][3] Long-term management may include physical therapy, hearing and vision aids, and regular exams to check for changes in vision, hearing, and muscle coordination.[1] 


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Absent tendon reflexes
Muscle weakness
Muscular weakness
Optic atrophy
Sensorineural hearing impairment
5%-29% of people have these symptoms
Abnormality of eye movement
Abnormal eye movement
Abnormal eye movements
Eye movement abnormalities
Eye movement issue

[ more ]

Autistic behavior
Cognitive impairment
Abnormality of cognition
Cognitive abnormality
Cognitive defects
Cognitive deficits
Intellectual impairment
Mental impairment

[ more ]

Poor swallowing
Swallowing difficulties
Swallowing difficulty

[ more ]

Pes cavus
High-arched foot
Percent of people who have these symptoms is not available through HPO
Autosomal dominant inheritance
Difficulty articulating speech
Lack of coordination of movement
Episodic generalized hypotonia
Gait ataxia
Inability to coordinate movements when walking
Weakness of one side of body
Difficulties in coordination
Incoordination of limb movements
Limb incoordination

[ more ]

Involuntary, rapid, rhythmic eye movements
Progressive sensorineural hearing impairment
Progressive visual loss
Progressive loss of vision
Progressive vision loss
Progressive visual impairment
Slowly progressive visual loss
Vision loss, progressive
Visual loss, progressive

[ more ]

Truncal ataxia
Instability or lack of coordination of central trunk muscles


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.[1][2][3]

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).[1][3] In some cases the signs and symptoms of these syndromes may overlap.[3]

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

In-Depth Information

  • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Cerebellar ataxia, areflexia, pes cavus, optic atrophy and sensorinural hearing loss. Click on the link to view a sample search on this topic.


  1. Brashear A, Sweadner KJ, Cook JF, et al. ATP1A3-Related Neurologic Disorders. GeneReviews. November 6, 2014; https://www.ncbi.nlm.nih.gov/books/NBK1115/.
  2. Chang IJ, Adam MP, Jayadev S, Bird TD, Natarajan N, Glass IA. Novel pregnancy-triggered episodes of CAPOS syndrome. Am J Med Genet. November 1, 2017; https://www.ncbi.nlm.nih.gov/pubmed/29090527.
  3. Duat Rodriguez A, Prochazkova M, Santos Santos S, Rubio Cabezas O, Cantarin Extremera V, Gonzalez-Gutierrez-Solana L. Early Diagnosis of CAPOS Syndrome Before Acute-Onset Ataxia-Review of the Literature and a New Family. Pediatr Neurol. June, 2017; 7160-64:https://www.ncbi.nlm.nih.gov/pubmed/28483396.

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