ring chromosome 20
Findings
No curated finding names ring chromosome 20 yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
Ring chromosome 20 syndrome is marked by a characteristic seizure phenotype. Depending on the amount of chromosomal loss and associated mosaicism, ring(20) can be associated with macrocephaly, mild to moderate intellectual deficit, or behavioral problems. In rare cases, brain, kidney or heart malformations may be present.
Definition from the Mondo Disease Ontology (MONDO:0015436), read 2026-09-29. CC BY 4.0.
Features
12 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.
- EEG abnormalityHPOHP:0002353
- Very frequent (80% to 99% of cases)
- Non-convulsive status epilepticus without comaHPOHP:0032671
- Very frequent (80% to 99% of cases)
- Atypical behaviorHPOHP:0000708
- Frequent (30% to 79% of cases)
- Epileptic encephalopathyHPOHP:0200134
- Frequent (30% to 79% of cases)
- Focal motor seizureHPOHP:0011153
- Frequent (30% to 79% of cases)
- Mental deteriorationHPOHP:0001268
- Frequent (30% to 79% of cases)
- Nocturnal seizuresHPOHP:0031951
- Frequent (30% to 79% of cases)
- Growth delayHPOHP:0001510
- Occasional (5% to 29% of cases)
- Intellectual disabilityHPOHP:0001249
- Occasional (5% to 29% of cases)
- Neurodevelopmental delayHPOHP:0012758
- Occasional (5% to 29% of cases)
- Short attention spanHPOHP:0000736
- Occasional (5% to 29% of cases)
- Specific learning disabilityHPOHP:0001328
- Occasional (5% to 29% of cases)
Where it sits
Other names
2 names
Resolves to: ring chromosome 20
- Also called
- ring chromosome 20 syndromering chromosome type 20