XXYY Syndrome

XXYY or 48,XXYY syndrome or 48,XXYY is a rare CTM intersex trait occurring in approximately 1 in 18,000 to 1 in 40,000 people assigned male at birth. It is a chromosomal condition that causes them to have an extra X and an extra Y chromosome (XXYY). It may be considered a variant of Klinefelter syndrome.

Those with the the condition typically have small testes that do not produce enough testosterone, which can lead to reduced facial and body hair, poor muscle development, breast growth, and infertility. Other common symptoms can include increased height, dental problems, problems with blood vessels in the legs, difficulty with language development, delayed development of motor skills, tremors that typically start in adolescence and increase with age, and an increased likelihood of several other physical and neurological conditions. They typically also have AMAB hypogonadism, and might also be classified under aromatase excess syndrome.

History
The first published report of an individual with a 48,XXYY karyotype was an AMAB individual by Sylfest Muldal and Charles H. Ockey in Manchester, England in 1960. It was described in a 15-year-old mentally challenged boy who showed signs of Klinefelter syndrome; however, chromosome testing revealed 48,XXYY instead of the 47, XXY arrangement known to cause Klinefelter syndrome. Because of this, 48,XXYY syndrome was originally considered a variation of Klinefelter syndrome.

Flag
The flag was coined by Deviantart user Pride-Flags on January 16th of 2017. It has no confirmed meaning.

The second flag was coined by Cryptocrew, specifically Adora, on May 4th of 2021. It uses some of the same colors of the original flag, but with added meaning. Dark blue represents being assigned male, light blue represents masculinity, white represents community and diversity, purple represents the intersex spectrum, light pink represents a lack of testosterone production, and dark pink represents feminine and androgynous traits. The design is made up of two X's and two Y's to represent the condition as a whole.