{"orpha":96055,"name":"Tetrasomy 21 syndrome","type":"Malformation syndrome","group":"Disorder","status":"active","flags":[],"synonyms":["Isochromosome 21"],"definition":"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.","note":null,"url":"https://raremap.alftech.space/d/ORPHA-96055/","orphanet_url":"https://www.orpha.net/en/disease/detail/96055","names":{"fr":{"name":"Syndrome de tétrasomie 21","synonyms":["Isochromosome 21"],"definition":"Une anomalie autosomique extrêmement rare causée par la présence de quatre copies du chromosome 21. Elle se caractérise par les signes cliniques de la trisomie 21 (incluant un retard de développement/déficit intellectuel, une hypotonie musculaire, un cou court avec une peau redondante, une brachycéphalie, une microcéphalie, un visage plat, un épicanthus, des fentes palpébrales obliques en haut et en dehors, de petites oreilles, une langue protrusive, un unique sillon palmaire transversal, une brachydactylie, des ailes iliaques hypoplasiques), associés à des signes additionnels, tels qu'un retard de croissance intra-utérine, une prématurité, un front haut et large, et un hypertélorisme. Des tumeurs malignes hématologiques sont aussi associées, et peuvent survenir plus tôt que dans la trisomie 21."},"de":{"name":"Tetrasomie 21","synonyms":["Isochromosom 21"],"definition":"Tetrasomie 21 ist eine extrem seltene autosomale Anomalie, die aus dem Vorhandensein von 4 Kopien des Chromosoms 21 resultiert und durch Merkmale der Trisomie 21 gekennzeichnet ist, einschließlich Entwicklungsverzögerung/Intelligenzminderung, muskuläre Hypotonie, kurzer Hals mit überflüssiger Haut, Brachyzephalie, Mikrozephalie, flaches Gesicht, Epikanthus, aufsteigende Lidachsen, kleine Ohren, herausstehende Zunge, einzelne transversale Palmarfalte, Brachydaktylie, hypoplastische Beckenflügel, zusammen mit zusätzlichen Merkmalen wie Frühgeburtlichkeit, intrauterine Wachstumsretardierung, hohe und breite Stirn sowie Hypertelorismus. Hämatologische Malignome sind ebenfalls assoziiert und können früher als bei Trisomie 21 auftreten."},"es":{"name":"Síndrome de tetrasomía 21","synonyms":["Isocromosoma 21"],"definition":"La tetrasomía 21 es una anomalía autosómica muy poco frecuente resultante de la presencia de 4 copias del cromosoma 21, caracterizada por los rasgos de la trisomía 21 incluyendo retraso del desarrollo / discapacidad intelectual, hipotonía muscular, cuello corto con piel redundante, braquicefalia, microcefalia, cara plana, epicanto, fisuras palpebrales inclinadas hacia arriba, orejas pequeñas, lengua protuberante, pliegue palmar transversal único, braquidactilia, alas ilíacas hipoplásicas, junto con características adicionales como prematuridad, retraso del crecimiento intrauterino, frente alta y ancha e hipertelorismo. También están asociadas neoplasias hematológicas que pueden desarrollarse antes que en la trisomía 21."},"it":{"name":"Sindrome tetrasomia 21","synonyms":["Isocromosoma 21"],"definition":"La tetrasomia 21 è un'anomalia autosomica molto rara, causata dalla presenza di quattro copie del cromosoma 21. È caratterizzata dai segni clinici della trisomia 21 (ritardo dello sviluppo/disabilità intellettiva, ipotonia muscolare, collo corto con cute ridondante, brachicefalia, microcefalia, viso piatto, epicanto, rime palpebrali oblique verso l'alto, orecchie piccole, lingua prominente, piega palmare trasversale unica, brachidattilia, ipoplasia delle creste iliache) associate a prematurità, ritardo della crescita prenatale, fronte alta e ampia e ipertelorismo. Possono associarsi tumori ematologici maligni, che esordiscono più precocemente rispetto alla trisomia 21."},"nl":{"name":"Tetrasomie 21-syndroom","synonyms":["Isochromosoom 21"],"definition":"Tetrasomie 21 is een uiterst zeldzame autosomale anomalie als gevolg van de aanwezigheid van 4 kopieën van chromosoom 21, en wordt gekarakteriseerd door kenmerken van trisomie 21, waaronder ontwikkelingsachterstand/intellectuele achterstand, spierhypotonie, korte hals met overtollige huid, brachycefalie, microcefalie, plat gelaat, epicanthus, opwaartse ooglidspleten, kleine oren, uitstekende tong, één enkele dwarse handlijn over de handpalm, brachydactylie, en hypoplastische bekkenvleugels, in combinatie met bijkomende kenmerken zoals vroeggeboorte, intra-uteriene groeiretardatie, hoog en breed voorhoofd, en hypertelorisme. Hematologische maligniteiten zijn ook geassocieerd en kunnen vroeger voorkomen dan bij trisomie 21."},"pt":{"name":"Tetrassomia 21"},"pl":{"name":"Zespół tetrasomii chromosomu 21","synonyms":["Izochromosom 21"]},"cs":{"name":"Tetrazomie 21","synonyms":["Izochromozom 21"]},"uk":{"name":"Тетрасомія 21","synonyms":["Ізохромосома 21"],"definition":"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."},"zh":{"name":"21四体","synonyms":["21号等臂染色体"],"definition":"21号染色体四体是一种极为罕见的常染色体异常，由4条21号染色体的存在所致，临床表现与21三体综合征相似，包括发育迟缓/智力障碍、肌张力减退、颈短伴蹼颈、短头畸形、小头畸形、扁平脸、内眦赘皮、上睑裂，小耳朵、舌头突出、通贯掌、短指/趾畸形、髂骨翼发育不良，以及其他一些附加特征，如早产、宫内发育迟缓、额头高而宽、眼间距过宽。可合并血液系统恶性肿瘤，并且可能比21三体综合征更早发生。"},"tr":{"name":"Tetrazomi 21","synonyms":["İzokromozom 21"]}},"xrefs":[{"source":"ICD-10","code":"Q99.8","qualifier":"NTBT","icd_relation":"attributed","validated":true},{"source":"ICD-11","code":"LD7Y","qualifier":"NTBT","icd_relation":"index","validated":true,"icd11_uri":"1246904243"},{"source":"MONDO","code":"0019864","qualifier":"E","icd_relation":null,"validated":true},{"source":"UMLS","code":"C4707057","qualifier":"E","icd_relation":null,"validated":true},{"source":"GARD","code":"12480","qualifier":"E","icd_relation":null,"validated":true}],"associations":[],"incoming_associations":[],"preferential_parent":{"orpha":93890,"name":"Rare developmental defect during embryogenesis"},"parents":[{"orpha":98132,"name":"Partial autosomal duplication/triplication syndrome","classifications":[147,156]}],"children":[],"genes":[],"genes_via_subtypes":[],"inheritance":[],"onset":["Antenatal","Infancy","Neonatal"],"prevalence":[{"type":"Cases/families","qualification":"Case(s)","class":null,"value":13.0,"area":"Worldwide","status":"Validated","source":"18372039[PMID]"},{"type":"Point prevalence","qualification":"Class only","class":"<1 / 1 000 000","value":0.0,"area":"Worldwide","status":"Validated","source":"ORPHANET_18372039[PMID]"}],"phenotypes":{"validation_status":"y","online":"y","validation_date":"2025-09-02","source":"31493343[PMID]_34472202[PMID]_3161017[PMID]","terms":[{"hpo":"HP:0000248","label":"Brachycephaly","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0001156","label":"Brachydactyly","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0001263","label":"Global developmental delay","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0001252","label":"Hypotonia","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0001249","label":"Intellectual disability","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0000252","label":"Microcephaly","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0010808","label":"Protruding tongue","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0000311","label":"Round face","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0000954","label":"Single transverse palmar crease","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0000474","label":"Thickened nuchal skin fold","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0000582","label":"Upslanted palpebral fissure","frequency":"Frequent (79-30%)","criteria":null},{"hpo":"HP:0001674","label":"Complete atrioventricular canal defect","frequency":"Occasional (29-5%)","criteria":null},{"hpo":"HP:0005280","label":"Depressed nasal bridge","frequency":"Occasional (29-5%)","criteria":null},{"hpo":"HP:0000316","label":"Hypertelorism","frequency":"Occasional (29-5%)","criteria":null},{"hpo":"HP:0000158","label":"Macroglossia","frequency":"Occasional (29-5%)","criteria":null},{"hpo":"HP:0001852","label":"Sandal gap","frequency":"Occasional (29-5%)","criteria":null},{"hpo":"HP:0005534","label":"Transient myeloproliferative syndrome","frequency":"Occasional (29-5%)","criteria":null}]}}