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.
Orphadata: Free access data from Orphanet. © INSERM 1999. Available on http: //www.orphadata.org. Data version September 2023.
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