Alkaptonuria

Alkaptonuria is a rare, usually autosomal recessive pathological change of tyrosine metabolism due to a defect or deficiency of the enzyme homogentisate dioxygenase ( EC 1.13.11.5 number ). This leads to increased formation of the degradation product homogentisate. Alkapton denotes the oxidized, black-brown form of Homogentisats, including in the urine, therefore alkaptonuria.

Disease

By damming of degradation products of tyrosine metabolism leads to crystal deposition in joints with gout -like arthritis and blackening of the cartilage ( ochronosis ). In the sclera of the eye caused dark spots. Furthermore, the disease can lead to kidney stones and calcification of the aortic valves.

Diagnostics

The urine color on addition of bases, such as NaOH, black.

Treatment

A method of treatment of the disease can be cured, is not known. Symptomatic treatment phenylalanine and tyrosine diet in combination with high doses of ascorbic acid (vitamin C) is recommended. However, this only has an effect if started in childhood. In later life they can change anything on the course.