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Spinocerebellar ataxia with axonal neuropathy type 1 is a rare, genetic neurological disorder characterized by a late childhood onset of slowly progressive cerebellar ataxia. Initial manifestations include weakness and atrophy of distal limb muscles, areflexia and loss of pain, vibration and touch sensations in upper and lower extremities. Gaze nystagmus, cerebellar dysarthria, peripheral neuropathy, stepagge gait and pes cavus develop as disease progresses. Cerebellar atrophy (especially of the vermis) is present in all affected individuals. Additional reported manifestations include seizures, mild brain atrophy, mild hypercholesterolemia and borderline hypoalbuminemia.
Features include always present findings: Shrinkage of the cerebellum (cerebellar atrophy), Dysarthria, Impaired vibratory sensation, and Decreased number of peripheral myelinated nerve fibers and others; and common findings: Brain shrinkage (cerebral atrophy), Decreased motor nerve conduction velocity, Impaired distal proprioception, and Steppage gait and others. 29 total HPO annotations.
Organ System | Phenotype Count | Example Features |
|---|---|---|
Brain and nerves | 12 | Peripheral axonal neuropathy, Brain shrinkage (cerebral atrophy), Steppage gait |
Muscles | 5 | Brain shrinkage (cerebral atrophy), Shrinkage of the cerebellum (cerebellar atrophy), Global brain atrophy |
Arms and legs | 2 | Impaired vibration sensation in the lower limbs, Distal lower limb muscle weakness |
Eyes | 1 | Gaze-evoked nystagmus |
Spinocerebellar ataxia with axonal neuropathy type 1 (SCAN1) is characterized by progressive ataxia, cerebellar atrophy, and distal sensorimotor axonal neuropathy based on findings in three persons in a consanguineous family from Saudi Arabia and four affected individuals from two apparently unrelated consanguineous families from Oman . The following description of the phenotypic features associated with this condition is based on these two reports. Cerebellar ataxia. Ataxic gait appears in the second decade of life between ages 13 and 15 years. The ataxia progresses slowly, initially manifesting as mild incoordination of the upper limbs and lower limbs and then progressing to inability to walk.
Source: GeneReviews — "Spinocerebellar Ataxia with Axonal Neuropathy Type 1"
TDP1 function has not been fully characterized.
Spinocerebellar ataxia, autosomal recessive, with axonal neuropathy 1 is associated with mutations in the TDP1 gene on chromosome 14.
No genotype-phenotype correlations are known as the data available are too limited .
Source: GeneReviews — "Spinocerebellar Ataxia with Axonal Neuropathy Type 1"
No consensus clinical diagnostic criteria for spinocerebellar ataxia with axonal neuropathy type 1 (SCAN1) have been published.
SCAN1 is suspected in individuals with the following clinical findings, electrophysiologic studies, laboratory findings, brain imaging, and family history .
Clinical findings
Slowly progressive disorder beginning in late childhood to early adulthood (ages 13-27 years)
Cerebellar ataxia manifesting initially as gait ataxia and subsequently as dysarthria
Distal sensorimotor neuropathy manifesting initially as areflexia and subsequently as weakness and loss of sensation
Cognitive dysfunction in some, manifesting as mild intellectual disability and poor executive function
Absence of:
Oculomotor apraxia
Extraneurologic findings
Source: GeneReviews — "Spinocerebellar Ataxia with Axonal Neuropathy Type 1"
Table 2. Genes of Interest in the Differential Diagnosis of Spinocerebellar Ataxia with Axonal Neuropathy Type 1
Gene | Disorder | MOI | Phenotype |
|---|---|---|---|
ABHD12 | Polyneuropathy, hearing loss, ataxia, RP, cataract (OMIM 612674) | AR | Pes cavus; Achilles tendon contractures; RP; ataxic /or spastic gait; progressive sensorimotor peripheral neuropathy |
APTX | Ataxia w/oculomotor apraxia type 1 (AOA1) (OMIM 208920) |
Genetic testing for TDP1 is available. Testing is considered confirmatory for diagnosis.
No approved treatments are currently available for spinocerebellar ataxia, autosomal recessive, with axonal neuropathy 1. The disease remains an area of unmet medical need.
No clinical practice guidelines for spinocerebellar ataxia with axonal neuropathy type 1 (SCAN1) have been published.
To establish the extent of disease and needs in an individual diagnosed with SCAN1, the evaluations summarized in this section (if not performed as part of the evaluation that led to the diagnosis) are recommended:
Complete neurologic examination including use of the Scale for the Assessment and Rating of Ataxia (SARA) and assessment of muscle strength, reflexes, and sensation
Assessment by specialists in rehabilitation medicine, occupational therapy, and physical therapy regarding gross motor skills, fine motor skills, and need for adaptive equipment such as prostheses, walking aids, and/or wheelchairs
Assessment by a speech-language pathologist for evidence of dysarthria and need for ongoing speech-language therapy
Consultation with a medical geneticist, certified genetic counselor, or certified advanced genetic nurse to inform affected individuals and their families about the nature, mode of inheritance, and implications of SCAN1 in order to facilitate medical and personal decision making
To support the family of an individual diagnosed with SCAN1, review of the following options is recommended:
Source: GeneReviews — "Spinocerebellar Ataxia with Axonal Neuropathy Type 1"
Likely to be extremely harmful and possibly fatal:
Exposure to genotoxic anti-cancer drugs such as camptothecins (e.g., irinotecan and topotecan) and bleomycin
Exposure to radiation
Source: GeneReviews — "Spinocerebellar Ataxia with Axonal Neuropathy Type 1"
Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.
Source: GeneReviews — "Spinocerebellar Ataxia with Axonal Neuropathy Type 1"
1 trial found
Routine follow up as determined by treating specialists is recommended to monitor the response to supportive care and to assess for changes in existing manifestations and/or emergence of new manifestations.
Source: GeneReviews — "Spinocerebellar Ataxia with Axonal Neuropathy Type 1"
Phenotype severity distribution: 5 always present features, 20 common features.
Estimated prevalence: <1 in 1,000,000 (VERY_RARE).
1 clinical trial registered, 1 recruiting. Interventions under study include other interventions. Research is primarily sponsored by academic and government institutions.
9 publications have been identified in PubMed for spinocerebellar ataxia, autosomal recessive, with axonal neuropathy 1. Research spans Case Report / Case Series (44%), Review / Meta-Analysis (22%), and Basic Science / Preclinical (22%).
Fogel BL (2025). [PMID: 40464291](https://pubmed.ncbi.nlm.nih.gov/40464291/). *Ann Neurol*. [Review / Meta-Analysis]
Rubio-Contreras D (2025). [PMID: 41315253](https://pubmed.ncbi.nlm.nih.gov/41315253/). *Cell Death Dis*. [Basic Science / Preclinical]
Rusecka JM (2025). [PMID: 40830689](https://pubmed.ncbi.nlm.nih.gov/40830689/). *J Appl Genet*. [Case Report / Case Series]
Mohammadi M (2025). [PMID: 39848142](https://pubmed.ncbi.nlm.nih.gov/39848142/). *Pediatr Neurol*. [Review / Meta-Analysis]
Aloisio S (2025). [PMID: 40824590](https://pubmed.ncbi.nlm.nih.gov/40824590/). *Neurol Sci*. [Case Report / Case Series]
Liampas A (2024). [PMID: 38683245](https://pubmed.ncbi.nlm.nih.gov/38683245/). *Mol Biol Rep*. [Case Report / Case Series]
Yahia A (2024). [PMID: 37012327](https://pubmed.ncbi.nlm.nih.gov/37012327/). *Eur J Hum Genet*. [Epidemiology / Natural History]
Kneer K (2024). [PMID: 38261029](https://pubmed.ncbi.nlm.nih.gov/38261029/). *J Neurol*. [Basic Science / Preclinical]
Ahmad R (2024). [PMID: 39576382](https://pubmed.ncbi.nlm.nih.gov/39576382/). *Mol Biol Rep*. [Case Report / Case Series]
Data assembled from 8 of 12 sources · Last updated Sep 20, 2026, 4:39 PM UTC
Online Mendelian Inheritance in Man
European rare disease database
Genetic and Rare Diseases Info Center
Early-onset cerebellar ataxia; axonal neuropathy; oculomotor apraxia; chorea or dystonia; serum concentration of albumin total cholesterol. AOA1 can be distinguished from SCAN1 by presence of oculomotor apraxia (80% of persons w/AOA1), but this sign is not obvious in the early stages of disease. ATM |
Ataxia-telangiectasia | AR | Telangiectasia; ataxia; cerebellar degeneration | — |
COA7 | Spinocerebellar ataxia w/axonal neuropathy 3 (OMIM 618387) | AR | Childhood onset; axonal motor sensory neuropathy; cerebellar ataxia cerebellum atrophy on MRI. Clinically similar to SCAN1. CYP27A1 |
Cerebrotendinous xanthomatosis | AR | Symmetric distal sensory loss weakness; cerebellar ataxia; upper motor signs; enlarged tendons | — |
ERCC4 | ERCC4-related xeroderma pigmentosum | AR | Freckle-like lesions, xerosis, poikiloderma on sun-exposed skin; ocular abnormalities; in 25% of affected persons, progressive neurologic abnormalities |
ERCC6 | ERCC6-related Cockayne syndrome | AR | ID; demyelinating neuropathy; retinopathy; congenital cataracts; joint contractures; prominent nasal bridge; sensorineural hearing loss; severe motor dysfunction |
FXN | Friedreich ataxia (FRDA) | AR | Slowly progressive ataxia; depressed tendon reflexes; dysarthria; muscle weakness; lower-limb spasticity; optic nerve atrophy; scoliosis; bladder dysfunction; loss of position vibration senses; onset age usually 25 yrs |
MRE11 | Ataxia-telangiectasia-like disorder (OMIM 604391) | AR | Similar to ataxia-telangiectasia; cerebellar degeneration; normal intellect |
PHYH | PHYH-related Refsum disease | AR | Childhood to adult onset; night blindness; demyelinating neuropathy; anosmia; ataxia; RP |
PNKP | Ataxia w/oculomotor apraxia type 4 (OMIM 616267) | AR | Childhood onset; dystonia; ataxia; oculomotor apraxia; cognitive impairment |
POLG | POLG-related ataxia neuropathy spectrum1 (See POLG-Related Disorders.) | AR | Adolescent to adult onset; sensory loss; ataxia; ophthalmoplegia SACS |
ARSACS | AR | Neuropathy; ataxia; spasticity; ID; prominent myelinated nerve fibers | — |
SETX | Ataxia w/oculomotor apraxia type 2 (AOA2) | AR | Early-onset cerebellar ataxia; axonal neuropathy; oculomotor apraxia; chorea or dystonia; serum alpha-fetoprotein (AFP) level |
SLC52A2 | SLC52A2-related riboflavin transporter deficiency | AR | Progressive bulbar palsy; childhood-onset sensorineural deafness; childhood-onset neuronopathy that is more prominent as upper... |
Source: GeneReviews — "Spinocerebellar Ataxia with Axonal Neuropathy Type 1"