What is Alkaptonuria?
Alkaptonuria is a genetic disease that happens when a person's body does not have the enzyme homogentisic dioxygenase (HGD). This enzyme helps break down a toxic compound called homogentisic acid, or HGA. When a person cannot break down HGA, it accumulates in the body and leads to a variety of health complications, many of which are not present until adulthood.
There are three main symptoms of Alkaptonuria. The first is HGA in the urine. This causes the urine to turn dark when it is exposed to air. However, darkening may not occur until several hours later. Many people with Alkaptonuria never notice this type of abnormal color to their urine. This may be the only sign of Alkaptonuria in children.
The second symptom is called ochronosis. This is a term that means a person's connective tissue has a bluish-black color. This color is caused by a buildup of HGA in connective tissue. People can see this coloring in the white parts of their eyes, ear cartilage, and on the skin of their hands from underlying tendons. People with Alkaptonuria may also see this coloring in their ear wax and in their sweat.
The last symptom is arthritis. People with Alkaptonuria typically have arthritis in their spine and in their large joints from the buildup of HGA.
Introne WJ, Perry MB, Troendle J, Tsilou E, Kayser MA, Suwannarat P, O'Brien KE, Bryant J, Sachdev V, Reynolds JC, Moylan E, Bernardini I, Gahl WA. A 3-year randomized therapeutic trial of nitisinone in alkaptonuria. Mol Genet Metab. 2011;103:307?14.
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