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Spinocerebellar Ataxia with Axonal Neuropathy, Autosomal Recessive.


GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2017.
2007 Oct 22 [updated 2012 Dec 20].

Author information

Department of Medical Genetics, University of British Columbia, Vancouver, Canada
Division of Pediatric Neurology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
Provincial Medical Genetics Program, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, Canada



Spinocerebellar ataxia with axonal neuropathy (SCAN1) is characterized by late-childhood-onset slowly progressive cerebellar ataxia, followed by areflexia and signs of peripheral neuropathy. Gaze nystagmus and cerebellar dysarthria usually develop after the onset of ataxic gait. As the disease advances, pain and touch sensation become impaired in the hands and legs; vibration sense disappears in hands and lower thigh. Individuals with advanced disease develop a steppage gait and pes cavus and eventually become wheelchair dependent.


Diagnosis is based on clinical findings, family history, MRI, and nerve conduction studies (NCS)/EMG. TDP1 is the only gene in which mutation is known to cause SCAN1.


Treatment of manifestations: Prostheses, walking aids, and wheelchairs help mobility; physical therapy may help maintain a more active lifestyle. Surveillance: Routine visits to the neurologist. Agents/circumstances to avoid: Because TDP1 codes for a DNA repair enzyme, genotoxic anti-cancer drugs such as camptothecins (e.g., irinotecan and topotecan) and bleomycin are likely to be extremely harmful and possibly fatal; exposure to radiation is likely to be extremely harmful and possibly fatal.


SCAN1 is inherited in an autosomal recessive manner. The parents of an affected child are obligate heterozygotes and therefore carry one mutant allele. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Once an at-risk sib is known to be unaffected, the risk of his/her being a carrier is 2/3. Carrier testing for at-risk family members is possible if the pathogenic variants in the family have been identified. Prenatal testing for pregnancies at increased risk is possible through laboratories offering either testing for the gene of interest or custom testing.

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