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Disease Profile

Harding ataxia

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.

1-9 / 100 000

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)

Cerebellar ataxia early onset with retained tendon reflex; EOCA; Ataxia, harding type


Congenital and Genetic Diseases; Nervous System Diseases


The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 1177

Early onset cerebellar ataxia with retained reflexes (EOCARR) or Harding ataxia is a cerebellar ataxia characterized by the progressive association of a cerebellar and pyramidal syndrome with progressive cerebellar ataxia, brisk tendon reflexes, and sometimes profound sensory loss.

The prevalence of EOCARR ataxia has been estimated to be around 1/100,000, and the birth prevalence at 1/48,000 births in North-western Italy.

Clinical description
EOCARR is a progressive cerebellar ataxia, with disease onset occurring in childhood or in juveniles (ranging from 3 to 20 years with a mean age of 9 years). EOCARR is characterized by dysarthria, gait ataxia, nystagmus, brisk tendon reflexes in the upper and lower limbs, absent ankle reflexes, and discrete or absent deep sensory loss. The association of brisk jerks and absent ankle reflexes may occur. Oculomotor disturbances, dysphagia, tremor, scoliosis, pes cavus, extensor plantar response, and lower limb wasting and weakness may be observed while amyotrophy is rarely observed. Moreover, spasticity may become progressively severe.

The exact etiology of EOCARR is still unknown. However, molecular genetic analysis in a Tunisian family confirmed the genetic heterogeneity of this syndrome and mapped the gene locus to chromosome 13q11-12.

Diagnostic methods
Diagnosis relies on physical examination as well as on imaging findings (magnetic resonance imaging (MRI) or computed tomography (CT)) revealing cerebellar atrophy. Peripheral nerve conduction and nerve biopsy findings may show moderate to severe axonal sensory-motor neuropathy with axonal regeneration.

Differential diagnosis
Differential diagnosis includes Friedreich ataxia (FRDA; in contrast to EOCARR shows cardiomyopathy, diabetes mellitus, scoliosis, skeletal deformities or optic atrophy), autosomal dominant cerebellar ataxia (ADCA), autosomal recessive spastic ataxia of Charlevoix-Saguenay, ataxia with vitamin E deficiency (see these terms), and inherited metabolic disorders that may express ataxia.

Genetic counseling
Transmission is autosomal recessive. The parents of an affected child should be informed of the 25% chance of transmitting the disease to future offspring.

Management and treatment
Treatment is symptomatic, aimed towards the control of spasticity, and should include physiotherapy and pharmacotherapy (that may include spasmolytic drugs such as baclofen).

The period of latency before becoming wheelchair-bound is significantly longer in EOCARR than in FRDA, resulting in a better prognosis in patients with EOCARR than in those with FRDA.

Visit the Orphanet disease page for more resources.


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
Progressive cerebellar ataxia
30%-79% of people have these symptoms
Abnormal pyramidal sign
Difficulty articulating speech
Poor swallowing
Swallowing difficulties
Swallowing difficulty

[ more ]

Hyperactive patellar reflex
Overactive knee reflex
Hyperreflexia in upper limbs
Jerky ocular pursuit movements
Lower limb hypertonia
Involuntary, rapid, rhythmic eye movements
Progressive gait ataxia
Sensory impairment
5%-29% of people have these symptoms
Abnormal EKG
Abnormal ECG
Cognitive impairment
Abnormality of cognition
Cognitive abnormality
Cognitive defects
Cognitive deficits
Intellectual impairment
Mental impairment

[ more ]

Decreased/absent ankle reflexes
Generalized amyotrophy
Diffuse skeletal muscle wasting
Generalized muscle degeneration
Muscle atrophy, generalized

[ more ]

Impaired visuospatial constructive cognition
Lower limb muscle weakness
Lower extremity weakness
Lower limb weakness
Muscle weakness in lower limbs

[ more ]

Lower limb spasticity
Pes cavus
High-arched foot


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

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    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

    • 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 Harding ataxia. Click on the link to view a sample search on this topic.