The Rare Intersection of HI and Turner Syndrome

Sometimes rare and super rare genetic conditions occur within the same child. That’s the case for Turner syndrome, which has an incidence rate of about 1 in 2,500 female births, and congenital hyperinsulinism, which happens about once in 50,000 births.

The risk of hyperinsulinism in girls with Turner syndrome is about 50-fold higher compared to the general population estimates. Turner syndrome is a genetic disorder resulting in short stature and lack of puberty, along with several other medical issues.

“Overall, it isn’t that common,” says Vicki Sanders, MS, LCGC, the genetic counselor for CHOP’s Congenital Hyperinsulinism Center. “But the overlap happens 48 times more frequently than it would by chance alone.”

Typically, a female has two X chromosomes. Turner syndrome (TS) results when a girl is missing all or part of one of the X chromosomes. The severity of symptoms of Turner syndrome can vary greatly, and sometimes a girl isn’t diagnosed until she reaches adolescence and fails to go through puberty. However, some children are diagnosed before they’re born (through prenatal genetic testing either with chorionic villus sampling, amniocentesis or blood tests). Others are diagnosed shortly after birth if they show some of the physical features, such as puffy feet or a webbed neck.

If a baby who is being evaluated for hyperinsulinism also has features suspicious for TS, she may have genetic testing that could indicate she has TS, too.

Girls with TS are at higher risk for problems with their kidneys, heart and thyroid. There are no common symptoms between HI and TS, however children who undergo a near-pancreatectomy for HI and girls with TS may both develop diabetes.

Researchers at Children’s Hospital of Philadelphia studied the medical records of girls with both TS and HI treated at the hospital between 1997 and 2017. Half of the dual diagnosed patients were responsive to diazoxide and had their HI medically managed. Of those that didn’t respond, half had pancreatectomies and half were managed with tube feedings and/or frequent feedings by mouth.

At CHOP, girls with TS and HI have the benefit of seeing experts in both conditions at the Turner Syndrome Program and the Congenital Hyperinsulinism Center.