49,XXXYY syndrome
MONDO:0016854
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.
Research intelligence
Directly mapped studies only · unique clinical trialsCurrent registry observations. Phase counts may overlap. Study start dates are not registry registration dates. Investigational interventions are not approved-treatment recommendations.
Medications under investigation
Verified disease and drug mappings that co-occur within the same study; not evidence of effectiveness.
MONDO disease family
Recruiting studies by city
Trial status
Trial phase
Study start year
Investigated drug interventions
XXXYY syndrome
XXXYY syndrome, also known as 49,XXXYY, is a chromosomal disorder in which a male has three copies of the X chromosome and two copies of the Y chromosome. XXXYY syndrome is exceptionally rare, with only eight recorded cases. Little is known about its presentation, but associated characteristics include intellectual disability, anomalies of the external genitalia, and characteristic physical and facial features. It is not caused by characteristics of the parents, but rather occurs via nondisjunction, a random event in gamete development. The karyotype observed in the syndrome is formally known as 49,XXXYY, which represents the 49 chromosomes observed in the disorder as compared to the 46 in normal human development. XXXYY syndrome was first recorded in 1963. Its long-term prognosis is poorly understood; while the condition as reported in the medical literature is relatively severe, it is unknown if there are milder cases that have not come to diagnostic attention.
Background only. Canonical identity remains MONDO; clinical-trial relationships come from ClinicalTrials.gov.Drugs being studied
Disease identity and terminology: MONDO. Trial relationships: ClinicalTrials.gov.