Ochronosis

As ochronosis ( from the ancient Greek ὠχρός, bright, light brown) is the brown-black pigmentation indicated by deposition of homogentisic acid polymer in the skin, connective tissue and cartilage. It is a consequence of the autosomal recessive alkaptonuria due to a genetic deficiency of homogentisate dioxygenase in liver and kidney.

Homogentisic acid is an intermediate of the phenylalanine and tyrosine metabolism, wherein the reduction results in a mangelhaftem Alkaptonuria. Homogentisic is excreted through the kidneys, which then oxidizes in air and urine - especially if this is alkaline - then brown-black colored ( " Schwarzharn 's disease "). The body itself is a polymeric quinoid dye formed in oversupply of homogentisic which penetrates well in collagen- rich tissues and leads to dark brown discoloration and degeneration. These collagen- rich tissues include:

• Sclera: not clinically disturbing, but a cosmetic problem
• Tendons
• Cartilage: Osteoarthritis ( osteoarthrosis deformans alcaptonurica )
• Vascular intima: atherosclerosis, high blood pressure, arterial occlusive disease, coronary heart disease, stroke
• Ossicles: hearing loss

• Metabolic disease