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Complete trisomy 20 syndrome

MedGen UID:
Concept ID:
Cell or Molecular Dysfunction
Synonyms: Chromosome 20 duplication; Chromosome 20, trisomy; Trisomy 20; Trisomy 20 mosaicism
SNOMED CT: Mosaic trisomy chromosome 20 (764624003); Trisomy 20 mosaicism (764624003); Mosaic trisomy 20 syndrome (764624003); Complete trisomy 20 syndrome (53346000)
Monarch Initiative: MONDO:0022757


A rare chromosomal anomaly syndrome with a highly variable phenotype ranging from normal (in the majority of cases) to a mild, subtle phenotype. Principal characteristics are spinal abnormalities (stenosis, vertebral fusion, and kyphosis), hypotonia, lifelong constipation, sloped shoulders, skin pigmentation abnormalities (linear and whorled naevoid hypermelanosis) and significant learning disabilities despite normal intelligence. More severe phenotypes, with patients presenting psychomotor and speech delay, mild facial dysmorphism, cardiac (ventricular septal defect, dysplastic tricuspid mitral valve) and renal anomalies (horseshoe kidneys) have also been reported. [from SNOMEDCT_US]

Recent clinical studies


Holzgreve W, Golabi M, Bradley J
Clin Genet 1986 Apr;29(4):342-4. doi: 10.1111/j.1399-0004.1986.tb01265.x. PMID: 2424648

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