Thousands of men may face increased risk of blood clotting diseases because they unknowingly carry an extra sex chromosome, British researchers have reported.
A new estimate of the proportion of men who carry an extra X or Y chromosome puts it at 1 in 500 – about seven times as many as who have been clinically diagnosed.
The finding comes from a study of the UK Biobank led by researchers at the universities of Cambridge and Exeter. In the study of more than 200,000 men of European ancestry aged 40 to 70, 213 were found to carry an extra X and 143 an extra Y. About 23% of the XXY men had already been diagnosed but only one of the XYY men.
Men with XXY chromosomes (known as Klinefelter syndrome) are already known to suffer from delayed puberty and infertility. The study confirmed this, but also found that the men with extra chromosomes faced a six times increased risk of suffering venous thrombosis and a three times increased risk of suffering from a pulmonary embolism.
They are also four times as likely as other men to suffer from chronic obstructive pulmonary disease and faced a three times increased risk of developing type 2 diabetes, according to the research, published in the journal Genetics in Medicine.
The researchers say they do not know why the extra chromosomes are linked to these increased risks. Body mass index, deprivation and smoking habits provided only a “partial” explanation, they report.
First author of the study Yajie Zhao said: “Even though a significant number of men carry an extra sex chromosome, very few of them are likely to be aware of this. This extra chromosome means that they have substantially higher risks of a number of common metabolic, vascular, and respiratory diseases – diseases that may be preventable.”
Prof Anna Murray from the University of Exeter, who co-supervised this work with Prof Ken Ong from Cambridge, said: “Our study is important because it starts from the genetics and tells us about the potential health impacts of having an extra sex chromosome in an older population, without being biased by only testing men with certain features as has often been done in the past.”
Source: Zhao Y, Gardner EJ, Tuke MA, Zhang H, Pietzner M, Koprulu M, Jia RY, Ruth KS, Wood AR, Beaumont RN, Tyrrell J, Jones SE, Lango Allen H, Day FR, Langenberg C, Frayling TM, Weedon MN, Perry JRB, Ong KK, Murray A. (2022) “Detection and characterisation of male sex chromosome abnormalities in the UK Biobank study.” Genetics in Medicine, doi: 10.1016/j.gim.2022.05.011
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