The HGD gene, also known as the homogentisate 1,2-dioxygenase gene, is the gene associated with alkaptonuria. Alkaptonuria is a rare inherited metabolic disorder characterized by the body’s inability to break down certain amino acids properly.
The HGD gene provides instructions for producing an enzyme called homogentisate 1,2-dioxygenase. This enzyme plays a crucial role in the breakdown of an amino acid called phenylalanine and the metabolism of another compound called tyrosine. Mutations in the HGD gene can lead to a deficiency or complete absence of the homogentisate 1,2-dioxygenase enzyme, resulting in the accumulation of homogentisic acid.
In individuals with alkaptonuria, the lack of functional homogentisate 1,2-dioxygenase enzyme causes homogentisic acid to accumulate in the body. This excess acid is excreted in the urine and can also be deposited in connective tissues, leading to a variety of symptoms, including darkening of urine when exposed to air, dark pigmentation of the skin, and progressive joint and cartilage damage.
Alkaptonuria is inherited in an autosomal recessive manner, which means that both copies of the HGD gene must be mutated to develop the disorder. Genetic testing can be used to identify mutations in the HGD gene and confirm a diagnosis of alkaptonuria.
