ochronosis

A rare, autosomal recessive disease characterized by alkapton uria with pigmentation of the cartilages and sometimes tissues such as muscle, epithelial cells, and dense connective tissue; may affect also the sclera, mucous membrane of the lips, and skin of the ears, face, and hands, and cause standing urine to be dark-colored and contain pigmented casts; pigmentation is thought to result from oxidized homogentisic acid, and cartilage degeneration results in osteoarthritis, particularly of the spine. [G. ochros, pale yellow, + nosos, disease]

- exogenous o. pigmentation of the skin of the face and elsewhere from prolonged topical exposure to hydroquinone-containing bleaching creams.

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ochro·no·sis .ō-krə-'nō-səs n, pl -no·ses -.sēz a condition often associated with alkaptonuria and marked by pigment deposits in cartilages, ligaments, and tendons

ochro·not·ic -'nät-ik adj

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n.

the presence of brown-black pigment in the skin, cartilage, and other tissues due to the abnormal accumulation of homogentisic acid that occurs in the metabolic disease alcaptonuria.

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ochro·no·sis (o″krə-noґsis) [Gr. ōchros pale + nos- + -sis] generalized deposition of dark pigment in the connective tissues, usually secondary to alkaptonuria (q.v.). It is characterized by urine that darkens on standing and visible dusky discoloration of the sclerae and ears. The pigment is a sequela of accumulation of homogentisic acid in the connective tissues. ochronotic adj

Dark pigmentation of ear cartilage in ochronosis.