49,XXXYY syndrome
MONDO:001685449, 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.
Also known as: 49, XXXYY syndrome, XXXYY syndrome
6 clinical trials for this condition and its sub-types.
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New study aims to unlock mysteries of sex chromosome disorders in children
Knowledge-focused ENROLLING_BY_INVITATIONThis study follows 300 fetuses and children with sex chromosome disorders to track their growth, organ development, and overall health. Researchers will also look at genetic and gut microbiome factors. The goal is to better understand how these conditions affect children over tim…
Sponsor: University of Aarhus • Aim: Knowledge-focused
Last updated Jun 27, 2026 08:11 UTC
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Scientists probe genetic secrets of lost fetuses to unravel sex chromosome mysteries
Knowledge-focused ENROLLING_BY_INVITATIONThis study looks at fetuses with sex chromosome disorders (like extra or missing X or Y chromosomes) that were either miscarried or electively aborted. Researchers will analyze the placenta and fetal tissues to see how the chromosome changes affect gene activity and development. …
Sponsor: University of Aarhus • Aim: Knowledge-focused
Last updated Jun 27, 2026 08:09 UTC
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10,000 genomes scoured for clues to rare brain diseases
Knowledge-focused ENROLLING_BY_INVITATIONThis study will analyze DNA from 10,000 people with suspected rare genetic disorders affecting the brain. Researchers will map structural changes in chromosomes to find which genes cause disease. The goal is to improve genetic diagnosis and lay groundwork for future treatments.
Sponsor: Karolinska Institutet • Aim: Knowledge-focused
Last updated Jun 26, 2026 13:56 UTC