ring chromosome 21
Findings
No curated finding names ring chromosome 21 yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
Ring chromosome 21 syndrome is an autosomal anomaly characterized by variable clinical features, most commonly including growth retardation, developmental delay, intellectual disability, epilepsy, microcephaly, short stature, dysmorphic features, hypogammaglobulinemia, thrombocytopenia and unspecific skeletal anomalies (hemivertebrae, clinodactyly, syndactyly). In rare cases, it has been described in phenotypically normal individuals.
Definition from the Mondo Disease Ontology (MONDO:0015437), read 2026-09-29. CC BY 4.0.
Features
30 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.
- Abnormal facial shapeHPOHP:0001999
- Very frequent (80% to 99% of cases)
- AmenorrheaHPOHP:0000141
- Frequent (30% to 79% of cases)
- EEG abnormalityHPOHP:0002353
- Frequent (30% to 79% of cases)
- Global developmental delayHPOHP:0001263
- Frequent (30% to 79% of cases)
- InfertilityHPOHP:0000789
- Frequent (30% to 79% of cases)
- Intellectual disabilityHPOHP:0001249
- Frequent (30% to 79% of cases)
- MicrocephalyHPO
Show the remaining 18
- ClinodactylyHPOHP:0030084
- Occasional (5% to 29% of cases)
- Cutaneous photosensitivityHPOHP:0000992
- Occasional (5% to 29% of cases)
- Decreased circulating immunoglobulin concentrationHPOHP:0004313
- Occasional (5% to 29% of cases)
- Delayed speech and language developmentHPOHP:0000750
- Occasional (5% to 29% of cases)
- Diabetes insipidusHPOHP:0000873
- Occasional (5% to 29% of cases)
- Fused thoracic vertebraeHPOHP:0030039
- Occasional (5% to 29% of cases)
Where it sits
Other names
3 names
Resolves to: ring chromosome 21
- Also called
- chromosome 21 en anneauChromosome 21 RingRing chromosome type 21