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spinocerebellar ataxia type 21 (SCA21) - Clinical Profile, Genes & Research | Kisho | Kisho

Rare Disease

spinocerebellar ataxia type 21

MONDO:0011833

Also known as:SCA21spinocerebellar ataxia 21

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Overview

Spinocerebellar ataxia type 21 (SCA21) is a very rare subtype of type I autosomal dominant cerebellar ataxia (ADCA type I). It is characterized by slowly progressive cerebellar ataxia, mild cognitive impairment, postural and/or resting tremor, bradykinesia, and rigidity.

GeneticsAutosomal dominant · TMEM240 (chr 1)

Clinical Trials1 registered · 1 recruiting

ResearchLimited published research (2 articles)

Clinical Presentation

Built from Human Phenotype Ontology (HPO) phenotype annotations and GeneReviews clinical descriptions. Features represent findings documented across known cases — not an exhaustive list of possible symptoms.

Features include always present findings: Gait ataxia and Ataxia; and common findings: Shrinkage of the cerebellum (cerebellar atrophy), Intention tremor, Nystagmus, and Mental deterioration and others. 30 total HPO annotations.

Organ System	Phenotype Count	Example Features
Brain and nerves	19	Scanning speech, Dystonia, Gait ataxia

Genetic Landscape

TMEM240 function has not been fully characterized.

Spinocerebellar ataxia type 21 is associated with mutations in the TMEM240 gene on chromosome 1.

Diagnosis

Genetic testing for TMEM240 is available. Testing is considered confirmatory for diagnosis.

Prognosis

Phenotype severity distribution: 2 always present features, 9 common features.

Estimated prevalence: <1 in 1,000,000 (VERY_RARE).

Research Landscape

Sourced from ClinicalTrials.gov and PubMed. Publication types are classified using NLM-curated article metadata; research type breakdowns reflect the nature of published work for this disease.

1 clinical trial registered, 1 recruiting. Interventions under study include other interventions. Research is primarily sponsored by academic and government institutions.

3 publications have been identified in PubMed for spinocerebellar ataxia type 21. Kisho has analyzed 2 by research type. Research spans Case Report / Case Series (100%).

Recent Publications

Mastrangelo M (2025). [PMID: 40602760](https://pubmed.ncbi.nlm.nih.gov/40602760/). *Neuropediatrics*. [Case Report / Case Series]
Yahya V (2024). [PMID: 39340213](https://pubmed.ncbi.nlm.nih.gov/39340213/). *Mov Disord Clin Pract*. [Case Report / Case Series]

Data assembled from 7 of 12 sources · Last updated Sep 18, 2026, 11:31 PM UTC

MONDOHPOClinicalTrials.govFDAPubMedHGNCClinVarClinGenGeneReviewsOrphanetOMIMRUSP

Medical References

External Resources

OMIM

Online Mendelian Inheritance in Man

OMIM:607454

Orphanet

European rare disease database

Orphanet:98773

GARD

Genetic and Rare Diseases Info Center

GARD:9999

Questions for Your Care Team

→Are any of the 1 active clinical trial a good fit for my situation?
→Should I pursue genetic testing for TMEM240, and what would the results mean for my family?
→Are there specialists or centers of excellence for this condition in my area?
→Is there a patient registry I should consider joining?

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spinocerebellar ataxia type 21

Overview

Clinical Presentation

Genetic Landscape

Diagnosis

Prognosis

Research Landscape

Recent Publications

Medical References

External Resources

OMIM

Orphanet

GARD

Related Diseases

Questions for Your Care Team

Questions for Your Care Team

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