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Alkaptonuria

What are the causes?

Alkaptonuria is caused by the deficiency of an enzyme known as homogentisic acid oxidase (HGAO). Normally, this enzyme performs a crucial step in a metabolic pathway by converting a chemical, homogentisic acid (HGA), into another form to meet the body's needs. As normal amounts of the HGAO enzyme are missing, HGA is not broken-down and accumulates in the body. Some is eliminated in the urine, and the rest is deposited in body tissues where it is harmful. The result is a blue-black discolouration of connective tissue including bone, cartilage and skin (otherwise known as ochronosis).

The build-up of HGA leads to premature progressive degeneration in the joints. Chronic joint pain is one of the first symptoms of Alkaptonuria. Arthritis of the spine, knees and hips causes symptoms of stiffness, pain, swelling and limited motion. Males tend to have an earlier onset of arthritic symptoms with a greater degree of severity than females. Deposits of pigment may cause cartilage to become brittle and eventually to fragment. 

View What are the symptoms? What are the symptoms?  |  How is it treated? View How is it treated?

Medical text written September 2003 by Contact a Family. Approved September 2003 by Dr L Ranganath, Consultant Physician in Clinical Chemistry, Liverpool University Medical School, Liverpool, UK.

 

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