spinocerebellar ataxia type 21
Findings
No curated finding names spinocerebellar ataxia type 21 yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
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.
Definition from the Mondo Disease Ontology (MONDO:0011833), read 2026-09-29. CC BY 4.0.
- Inheritance
- Autosomal dominant inheritance
- Onset and course
- Middle age onset · Neonatal onset · Childhood onset
HPO, annotations 2026-09-02
Features
27 features
What the disease is reported to present with, and how often among people who have it — never how often a feature means the disease. HPO, annotations 2026-09-02.
- AtaxiaHPOHP:0001251
- 5 of 5 reported patients
- Gait ataxiaHPOHP:0002066
- 5 of 5 reported patients
- Very frequent (80% to 99% of cases)
- Abnormality of extrapyramidal motor functionHPOHP:0002071
- Very frequent (80% to 99% of cases)
- Intermittent microsaccadic pursuitsHPOHP:0007944
- Very frequent (80% to 99% of cases)
- Progressive cerebellar ataxiaHPOHP:0002073
- Very frequent (80% to 99% of cases)
- Cerebellar atrophyHPOHP:0001272
- 3 of 4 reported patients
Show the remaining 15
- Intellectual disabilityHPOHP:0001249
- 2 of 5 reported patients
- Frequent (30% to 79% of cases)
- Mental deteriorationHPOHP:0001268
- 3 of 5 reported patients
- NystagmusHPOHP:0000639
- 2 of 5 reported patients
- Frequent (30% to 79% of cases)
- Postural tremorHPOHP:0002174
- 3 of 5 reported patients
- RigidityHPOHP:0002063
- Frequent (30% to 79% of cases)
- TremorHPOHP:0001337
- Frequent (30% to 79% of cases)
Genes
1 gene
Germline variants in the gene encoding each protein, as classified by GenCC submitters, each in their own words. Limited, disputed and refuted submissions are listed too.
- TMEM240HGNC:25186
- Definitive · G2P · Autosomal dominant · 2021
- Strong · Genomics England PanelApp · Autosomal dominant · 2021
- Strong · Labcorp Genetics (formerly Invitae) · Autosomal dominant · 2022
- Strong · PanelApp Australia · Autosomal dominant · 2025
- Moderate · Ambry Genetics · Autosomal dominant · 2020
- Supportive · Orphanet · Autosomal dominant · 2021
Where it sits
Other names
1 name
Resolves to: spinocerebellar ataxia type 21
- Also called
- SCA21