Histidinemia is an inherited condition characterized by elevated levels of histidine in blood, urine, and the fluid that surrounds the brain and spinal cord (cerebrospinal fluid). Histidine is an amino acid that acts as a building block for many different proteins.

Histidinemia is caused by variants (also called mutations) in the HAL gene, which provides instructions for making an enzyme called histidase. Histidase breaks down histidine that the body gets from food. Histidase is active (expressed) primarily in the liver and the skin.

Since many people who have histidinemia do not have signs and symptoms, it is hard to know exactly how many people have the condition. The condition appears to be more common among people of Japanese descent and among the French Canadian population in Quebec, Canada.

This condition is typically inherited in an autosomal recessive pattern, which means both copies of the gene in each cell must have a variant to cause the disorder. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene.

Published Date: June 03, 2024
Published By: National Institutes of Health