XYYYY syndrome
XYYYY syndrome is a very rare genetic disorder. Males usually have one X chromosome and one Y chromosome, but people with this condition have three extra Y chromosomes. They have a total of 49 chromosomes instead of 46. Only twelve known cases of it have been diagnosed and it is believed to have a frequency of less than one in one million. Little is known about XYYYY syndrome.
| XYYYY syndrome | |
|---|---|
 | |
| Man with XYYYY syndrome | |
| Usual onset | Prenatal |
| Duration | Lifelong |
| Diagnostic method | Karyotype |
| Frequency | Less than 1 in 1,000,000 |
Symptoms
The symptoms of XYYYY syndrome largely vary. Physical traits include hypertelorism (wide-spaced eyes), low-set ears, radioulnar synostosis (fusion of the radius and ulna bones in the arm), and clinodactyly (curved finger, usually the fifth finger).[1] In other disorders that affect the Y chromosome, like XYY syndrome and XYYY syndrome, a tall height is common, but this is not true for XYYYY syndrome.[2][3] The genitalia in people with XYYYY is normal, but azoospermia is common. This means the person cannot produce sperm and is infertile.[4]
Mentally, mild to moderate intellectual disability has been found in every case.[3] Autism and attention-deficit hyperactivity disorder are also common.[5]
History
XYYYY syndrome was first found in 1968. This case was mosaic, meaning some cells had one X chromosome and four Y chromosomes but others did not. Mosaicism is common in this condition.[6] Of the twelve known cases, seven were not mosaic while the other five were.[5] Some of the other chromosomes that the mosaic cells had alongside XYYYY in some people with the condition are X0 and XYYY. The first non-mosaic case (meaning every cell had one X chromosome and four Y chromosomes) was found in a 14-month-old boy 1981.[6] When the boy was 7, a follow-up was done. This was the only long-term follow-up of XYYYY syndrome.[3]
Prevalence
It is estimated that less than one in one million males have XYYYY syndrome.[7]
References
- ↑ Linden, Mary C.. Sex Chromosome Tetrasomy and Pentasomy. Pediatrics 96 (4) (1995-10-01). p. 672–682. doi:10.1542/peds.96.4.672. Retrieved 2024-01-08.
- ↑ Bartholdi, Deborah. Y Polysomies, in Males (in en). Encyclopedia of Molecular Mechanisms of Disease (2009). Berlin, Heidelberg: Springer. p. 2265–2266. ISBN 978-3-540-29676-8. doi:10.1007/978-3-540-29676-8_1908. Retrieved 2025-01-08.
- ↑ 3.0 3.1 3.2 Frey-Mahn, Gabriele. Y chromosomal polysomy: A unique case of 49,XYYYY in amniotic fluid cells (in en). American Journal of Medical Genetics Part A 118A (2) (2003). p. 184–186. doi:10.1002/ajmg.a.10051. Retrieved 2024-01-08.
- ↑ Linden, Mary C.. Sex Chromosome Tetrasomy and Pentasomy. Pediatrics 96 (4) (1995-10-01). p. 672–682. doi:10.1542/peds.96.4.672.
- ↑ 5.0 5.1 Autism spectrum disorder associated with 49,XYYYY: case report and review of the literature. BMC Medical Genetics 18 (9) (2017). p. 9. doi:10.1186/s12881-017-0371-1.
- ↑ 6.0 6.1 Sirota, L.. 49, XYYYY. A case report (in en). Clinical Genetics 19 (2) (1981). p. 87–93. doi:10.1111/j.1399-0004.1981.tb00676.x. Retrieved 2025-01-08.
- ↑ Orphanet: 49,XYYYY syndrome. www.orpha.net. Retrieved 2025-01-08.