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.

 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). 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. The genitalia in people with XYYYY is normal, but azoospermia is common. This means the person cannot produce sperm and is infertile.

Mentally, mild to moderate intellectual disability has been found in every case. Autism and attention-deficit hyperactivity disorder are also common. 

 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. Of the twelve known cases, seven were not mosaic while the other five were. 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. When the boy was 7, a follow-up was done. This was the only long-term follow-up of XYYYY syndrome.

 Prevalence 
It is estimated that less than one in one million males have XYYYY syndrome.

 References 

Category:Genetic disorders