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Infantile-onset spinocerebellar ataxia (IOSCA) is a hereditary neurological disorder with early and severe involvement of both the peripheral and central nervous systems. It has only been described in Finnish families.
Features include always present findings: Encephalopathy, Low muscle tone (hypotonia), Sensory axonal neuropathy, and Epilepsia partialis continua and others; and common findings: Hearing loss (hearing impairment), Distal amyotrophy, Ataxia, and Fiber type grouping and others. 36 total HPO annotations.
Organ System | Phenotype Count | Example Features |
|---|---|---|
Brain and nerves | 17 | Encephalopathy, Cerebral cortical atrophy, Ataxia |
Muscles | 8 | Shrinkage of the cerebellum (cerebellar atrophy), Cerebral cortical atrophy, Low muscle tone (hypotonia) |
Lab test results | 2 | Elevated circulating alanine aminotransferase concentration, Elevated circulating aspartate aminotransferase concentration |
Eyes | 2 | Nystagmus, Damage to the optic nerve (optic atrophy) |
Digestive system | 2 | Difficulty swallowing (dysphagia), Vomiting |
Ears | 1 | Hearing loss (hearing impairment) |
Hormones | 1 | Hypergonadotropic hypogonadism |
TWNK function has not been fully characterized.
Mitochondrial DNA depletion syndrome 7 (hepatocerebral type) is associated with mutations in the TWNK gene on chromosome 10.
Genetic testing for TWNK is available. Testing is considered confirmatory for diagnosis.
Phenotype severity distribution: 12 always present features, 11 common features.
Estimated prevalence: <1 in 1,000,000 (VERY_RARE).
No clinical trials have been registered for mitochondrial DNA depletion syndrome 7 (hepatocerebral type).
2 publications have been identified in PubMed for mitochondrial DNA depletion syndrome 7 (hepatocerebral type). Research spans Review / Meta-Analysis (50%) and Epidemiology / Natural History (50%).
Bao S (2025). [PMID: 40556660](https://pubmed.ncbi.nlm.nih.gov/40556660/). *Frontiers in cardiovascular medicine*. [Review / Meta-Analysis]
Buianova AA (2024). [PMID: 39684270](https://pubmed.ncbi.nlm.nih.gov/39684270/). *International journal of molecular sciences*. [Epidemiology / Natural History]
Data assembled from 6 of 12 sources · Last updated Sep 20, 2026, 5:39 PM UTC
Online Mendelian Inheritance in Man
European rare disease database
Genetic and Rare Diseases Info Center