Metabolic disorders cause developmental impairment in children more often than had been expected. Over the past five years, researchers at the Sylvia Tóth Center at University Medical Center (UMC) Utrecht were able to find the cause of mental impairment in 59 out of 433 children; in 12 cases the reason for the impairment was a metabolic disorder. The results were recently published online in the medical journal Annals of Neurology.
Patients come to the Sylvia Tóth Center when the general practitioner and pediatrician are unable to find out why a child is lagging behind mentally. In the end, the specialists at UMC Utrecht were able to arrive at a diagnosis for 59 of the 433 children who had been referred to the center. In 35 cases the cause was genetic. For the other 24 children there was an external cause involving such things as parenting problems or problems during childbirth. The average age of the children was just over four and a half.
Although most of the children had already been tested for metabolic disorders, for 12 of them, metabolic disorders turned out to be what was causing their mental impairment. This amounts to 2.8 percent, and is much higher than what had been anticipated based on earlier research. According to pediatrician Dr. Gepke Visser, final author of the article, “What this says is that, if you look hard enough, it’s still possible to find diseases in a group that has already been screened.” At the Sylvia Tóth Center, doctors examine things like blood and urine for indications of a defective metabolism.
This yields a high number of diagnoses, says Visser. “It may not seem like much, but the group of children in question had already undergone a lot of testing and no cause had been found. The fact that we were nonetheless able to make a diagnosis in 59 of the children is very important. Sometimes a special diet or enzyme therapy can make it possible to treat a metabolic disorder.”
Heel-prick screening was expanded in January of 2007 in the Netherlands, and newborns are now tested for sixteen different diseases. But there are around a thousand different metabolic disorders, and some of these can be treated. For this reason, Visser says that even after heel-prick screening has taken place, metabolic disorders should still be considered as a possible cause of mental retardation.