What Your Test Results Mean:

Carriers typically show no symptoms of this disorder; however, carriers are at an increased risk for having a child born with this condition. Risk for current or future pregnancies depends on the partner’s carrier status. Consultation with a genetic counselor is recommended.

Disease Explained:

Alkaptonuria is an inherited disorder caused by an enzyme deficiency that results in a build up of homogentisic acid in the body. Over time, this causes the connective tissues to darken. Homogentisic acid is also excreted in urine, which turns the urine black upon immediate exposure to air. This condition can also cause arthritis, heart problems, kidney stones, and prostate stones. Management is symptomatic and there are no treatments available.

How the Genetics Works:

Alkaptonuria is an autosomal recessive disorder caused by pathogenic variants in the HGD gene. In general, individuals have two copies of the HGD gene. Carriers of alkaptonuria have a single variant in one copy of the HGD gene while individuals with alkaptonuria have variants in both copies of their genes, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.