Pentasomy X

Pentasomy X or 49,XXXXX is an intersex trait in which an AFAB individual is born with five X chromosones. This is usually due to having older parents than the average parental age, in which their reproductive system is no longer fully working. This may also be caused from another abnormality or another form of failure in the parents reproductive system.

Some traits that typically come along with this condition includes a small head, decreased muscle tone, ear abnormalities, widely spaced eyes, a short neck, a broad nose with a depressed nasal bridge, hyperextension of the elbows, dental abnormalities and a cleft palate, deformities of the feet, heart defects, and an abnormally bent pinkie finger.

This intersex trait appears to be extremely uncommon, and only forty cases have been submitted since its discovery.

History
The syndrome was originally described in 1963 by Kesaree and Wooley.

Resources

 * https://en.wikipedia.org/wiki/Pentasomy_X#cite_note-NORD2003-2
 * https://rarediseases.org/rare-diseases/penta-x-syndrome/