One in 500 men carry extra sex chromosome, research suggests

According to the researchers, twice as many men have an extra sex chromosomes as previously thought.

One in 500 men in the general population has an extra X or Y chromosomes, double the number found in earlier work, according to research on more than 200,000 men who have joined the UK Biobank.

While most men have one X and one Y chromosomes, some are born with two, putting them at increased risk of health issues such as type 2 diabetes, blocked blood vessels and COPD.

A senior author on the study said they were surprised at how common it is. It had been thought to be uncommon.

The Cambridge team looked at the genetics of over 200,000 men from 40 to 70 years of age. There are 231 men with an extra X and 73 men with an extra Y. One in 500 men in the general population carry an extra X or Y chromosomes, according to the scientists.

There was little awareness of the condition among the men who were flagged up in the study.

Men with an extra X chromosome are more likely to be diagnosed with puberty and fertility related issues, as well as higher body fat, cognitive problems and personality disorders. There was a threefold greater risk of delayed puberty and a fourfold greater risk of being childless in the study. The effects of an extra Y are unknown. Men with X chromosomes tend to be taller than boys and have normal reproductive function.

According to previous research, about 1 in 1,000 women carry an additional X chromosomes, which can lead to similar effects, such as slower growth until puberty, delayed language development and reduced IQ.

The risk of several medical conditions was found in the analysis of the men's health records. Carrying an extra sex chromosomes tripled the risk of type 2 diabetes, blocked blood vessels in the lungs, and raised the risk of blocked veins compared to XY men, according to a study. It's not clear why the extra chromosomes have an impact and why it's the same regardless of the duplicated chromosomes.

Delayed puberty and infertility, as well as some men presenting with diabetes and clotting problems, should be the focus of more genetic testing. Doctors probably aren't looking for genetic tests for some of these conditions. Patients with these conditions should be encouraged to have genetic tests.