Diagnostic Test Developed for Hereditary Children's Disease

Researchers have developed a diagnostic test to successfully diagnose Idiopathic Infantile Hypercalcemia (IIH), a hereditary childhood disease which is estimated to affect over 6,000 Americans.

IIH is one of the top ten most commonly inherited diseases; it blocks the body from breaking down vitamin D, which results in an excess of calcium in the blood. Children suffering from IIH endure calcifications and hardening tissue throughout their bodies, along with calcification of the kidneys and renal failure.

Researchers have previously estimated that it effects one in every 47,000 people—roughly 6,000 Americans. Until a recent breakthrough in genetic research, however, there was never a way to confirm this estimation.

The breakthrough has led to the discovery of the defect behind IIH, and as such, researchers have been able to develop the first genetic and biochemical test which positively identifies IIH in individuals.

“Developing a positive diagnostic test for IIH is a major step in understanding this disease,” reported co-lead researcher Glenville Jones, a professor in the Department of Biomedical and Molecular Sciences.

The researchers studied six children from four families with suspected autosomal recessive inheritance of the condition. Four of the children studied presented with symptoms after receiving oral vitamin D supplementation—500 IU every day since birth—while two siblings were asymptomatic.

Further, four more patients were genotyped when they developed severe hypercalcemia within weeks of receiving a regiment of 600,000 IU prophylactic bolus of vitamin D₂.

The researchers reported that that their findings indicated a mutation in an enzyme—CYP24A1—which is responsible for encoding the key enzyme of vitamin D₃ degradation may be the cause of IIH. This mutation was recorded in both familial cases and in infants who developed severe hypercalcemia after bolus vitamin D prophylaxis, according to Martin Konrad, MD, of University Children's Hospital in Muenster, Germany.

"I think this is going to lead to a better diagnosis for the patients with this condition," Jones said. "We will be able to tell them apart from the general population at an earlier stage."

As with most diseases, early detection of IIH is the key to disease management. Detection and diagnosis of the disease, which has been very difficult to do in the past, will greatly improve the care children with IIH will receive.

The researchers now hope to see the tests get developed commercially.

The study was published in the New England Journal of Medicine.