What happens when you expect an extra X or Y . chromosome

Katie and her husband, Simon, had never heard of XXY, and their obstetrician wasn’t much help either. Also known as Klinefelter syndrome, XXY is an inherited condition that can cause infertility and other health problems; it occurs when a child, usually designated as male at birth, is born with an extra X chromosome in addition to the usual X and Y.

Sex chromosome variants, in which those with an extra or missing X or Y, are the most common chromosomal condition, occurring in one in 400 births. However, the majority of those affected don’t even know they have the disease. That’s because these conditions can fly under the radar; they’re not life-threatening or even necessarily life-limiting, and don’t usually have narrative features that get you red flags. However, the diagnosis can be distressing.

As many parents-to-be opt for non-invasive prenatal testing in the hope of ruling out serious conditions, many of them are surprised to discover that their unborn baby has a less serious condition. more – but less well known. Because so many sex-chromosomal variants have historically gone undiagnosed, many pregnant women are unfamiliar with these conditions, leaving families to find out for themselves the unexpected news. Many people seek information from advocacy organizations, genetic counselors, even Instagram as they figure out their next steps..

The information landscape has changed dramatically since the advent of noninvasive prenatal screening (NIPS) a decade ago. The increasingly popular first-trimester blood tests launched in 2011 to detect Down syndrome have, over time, added a wide range of conditions to their table, including chromosomal anomalies. count – the medical name of an atypical chromosome number.

“The scariest part here is that this diagnosis is based on a test that we don’t really understand.”

In 2020, the American College of Obstetricians and Gynecologists endorsed NIPS in all ages, effectively making blood testing a routine part of pregnancy care. Parents often use these tests to rule out Down syndrome or more serious conditions, only to find out in many cases about something they don’t even realize their child is being screened for. filter. “The scariest part here is that this diagnosis is based on a test that we don’t really understand,” says Simon. Katie added: “We assumed the test would only detect very serious things.”

To add complexity, NIPS is not as reliable for sex-chromosomal aneuploidies as it is for Down syndrome, underscoring the importance of confirming a positive screening result in pregnancy through amniocentesis. amniocentesis or chorionic villus sampling (testing of placental tissue) or with a blood sample after the baby is born. However, the data shows that “some women chose to have an abortion solely on the basis of [noninvasive prenatal screening] results, potentially unaffected abortion,” according to a 2016 article in the journal Prenatal Diagnosi.S.

Nicole Tartaglia, a global expert on sex chromosome variants, says about 40% of men with XXY are diagnosed during their lifetime, often when they experience fertility problems when mature. People with XXY may have learning difficulties and social challenges, along with physical characteristics such as small testicles, less muscular body, and less facial and body hair. But most people with Klinefelter syndrome grow up to live healthy and productive lives.

Meanwhile, only 10% of people with XXX or XYY are aware of their condition. But these numbers are growing as genetic testing grows in popularity. “Judging by the number of calls we receive, the percentage of people going undiagnosed is decreasing,” she said.

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