Tetrasomy 21
Synonyms: Isochromosome 21
Tetrasomy 21 is an extremely rare autosomal anomaly resulting from the presence of 4 copies of chromosome 21 characterized by features of trisomy 21 including developmental delay/intellectual disability muscular hypotonia short neck with redundant skin brachycephaly microcephaly flat face epicanthus upslanted palpebral fissures small ears protruding tongue single transverse palmar crease brachydactyly hypoplastic iliac wings together with additional features such as prematurity intrauterine growth retardation high and broad forehead hypertelorism. Haematological malignancies are also associated and may occur earlier than in trisomy 21.
Data from Orphanet are used to provide information on a disease's name, synonym(s), and overview.
Reference: Access aggregated data from Orphanet at Orphadata.
Orphadata: Free access data from Orphanet. © INSERM 1999. Available on http: //www.orphadata.org. Data version September 2023.
Newly diagnosed with
Tetrasomy 21?
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Advocacy Organizations
Rare Chromosome Disorder Support Group – Unique
To inform, support and alleviate the isolation of anyone affected by a rare chromosome or single gene disorder and to raise public awareness.
Syndromes Without A Name (SWAN) Australia
Provide information, support and advocacy to families caring for a child with an undiagnosed or rare genetic condition.
Clinical Trials
For a list of clinical trials in this disease area, please click here.