XXXXY Syndrome

49,XXXXY syndrome, also sometimes known as Fraccaro Syndrome, is an extremely rare intersex trait in AMAB individuals in which they have three extra X chromosomes. It occurs in approximately 1 out of 85,000 - 100,000 AMAB individuals. Symptoms of 49,XXXXY syndrome can vary, but usually include learning difficulties/intellectual disabilities, low muscle tone, hypogonadism, infertility, delayed growth, distinctive facial features, and a variety of birth defects that may affect the heart, bones, brain and/or kidneys.

History
It was first diagnosed in 1960, and was named Fraccaro syndrome after the researcher.

Resources

 * https://en.wikipedia.org/wiki/49,XXXXY
 * https://medlineplus.gov/genetics/condition/49xxxxy-syndrome/
 * https://rarediseases.info.nih.gov/diseases/5679/49-xxxxy-syndrome