49,XXXYY syndrome https://github.com/monarch-initiative/mondo/issues/4272 https://rarediseases.info.nih.gov/diseases/10922/49-xxxyy-syndrome https://www.malacards.org/card/49xxxyy_syndrome MONDO:0016854 XXXYY syndrome Orphanet:261534 49, XXXYY syndrome is a chromosome abnormality that occurs when a male inherits two extra copies of the X chromosome and one extra copy of the Y chromosome. The condition is extremely rare with only a handful of cases reported in the medical literature. Signs and symptoms associated with these cases include severe intellectual disability, distinctive facial features, normal to tall stature, gynecomastia, hypogonadism, and behavioral abnormalities. 49, XXXYY syndrome is likely caused by a mistake (called nondisjunction) that occurs at conception or during the formation of the sperm and/or egg. Treatment is based on the signs and symptoms present in each person. GARD:0010922 49, XXXYY syndrome MEDGEN:1667231 UMLS:C4749586 chromosome X disorder chromosome Y disorder aneuploidy