Exogenous ochronosis superimposed on chronic kidney disease: A case report and review of literature

Ochronosis is a rare disease characterized by speckled and diffuse pigmentation symmetrically over the face, neck, and photo-exposed areas. It can present in exogenous or endogenous form. Endogenous ochronosis or alkaptonuria is an autosomal recessive disease caused by a deficiency of homogentisic acid (HGA) oxidase, which results in the accumulation of HGA, a hydroquinone (HQ) metabolite of tyrosine. Some evidence suggests that it is not HGA itself but a by-product of its oxidation, a benzoquinone acetic acid, that can polymerize to a melanin-like pigment by unknown mechanisms and accumulates both inter and intracellularly in connective tissue, most commonly the joints, cardiovascular system, kidney, skin, and glands, a pathological condition known as ochronosis (Development of an in vitro model to investigate joint ochronosis in alkaptonuria. Tinti L, Taylor AM et al. Rheumatology 2010; Oct 15: 1-7. doi: 10.1093/rheumatology/keq246). Exogenous ochronosis (EO) is a rare, cosmetically disfiguring condition, resulting from the long-term use of topical HQ in the treatment of melasma. It manifests as grey-brown or blue-black macules in HQ-exposed regions, characterized histologically by banana-shaped ocher-colored deposits in the dermis. HQ the topical bleaching agent of choice is widely prescribed by physicians and often used by patients without a prescription. The principal adverse effects of its chronic use are confetti-like depigmentation and rarely EO. EO is an avoidable dermatosis that needs to be recognized early with immediate discontinuation of HQ as treatment is difficult. Sun exposure facilitates the formation of EO and must be strictly avoided. We report case of a 65-year-old man who had chronic kidney disease but developed EO while using topical HQ