One in 400 males have an additional X or Y chromosome, however 86% of these individuals are not diagnosed.
This is according to a study – “Prevalence, Morbidity, and Mortality of Men With Sex Chromosome Aneuploidy in the Million Veteran Program Cohort” by Shanlee M. Davis, Craig Teerlink, Julie A. Lynch, et al – that was published in JAMA Network Open.
Men with an extra X chromosome, known as Klinefelter syndrome, or Y chromosome, also known as Jacobs syndrome, have an increased risk of delayed development, learning disabilities, type 2 diabetes, and cardiovascular disorders. Men with Klinefelter syndrome also have impaired testicular function associated with low testosterone and infertility. Unfortunately, all of the research on these conditions is from the <15% who are clinically diagnosed, and are almost entirely of Western European ancestry.
For this study, nearly 600,000 veterans in the Million Veteran Program (MVP) were involved. And through genetic analysis, extra X was found in 862 men and an extra Y in 747 men – similar rates to the general population.
Unexpectantly, this research revealed that white and Asian veterans had the highest prevalence of the syndromes with black and Hispanic veterans having the least. Most do not know about their extra X or Y, but those without a clinical diagnosis were similarly affected to those who were previously diagnosed.
Considering that the participants came from the military, the researchers noted that men with X and Y variations can successfully serve in the military “but experience many medical and psychiatric comorbidities that could potentially be prevented with appropriate diagnosis and care.”
“There’s still a lot we don’t know about these men who have gone years without a proper diagnosis,” Davis said. “Studying this aging population will allow us to learn the risks associated with extra X and Y chromosomes, even when we do not know about the genetic difference clinically. Early identification of these conditions, which is now often happening prenatally, gives us an opportunity to prevent some of the illnesses associated with Klinefelter and Jacobs syndromes.”
