To the Editor.—
I was interested to read the article by Hoshaw et al1 in the January 1985 Archives describing ochronosislike pigmentation from hydroquinone bleaching creams in American blacks. We have recently had the opportunity to evaluate a similar case. In reviewing the literature concerning the biochemical pathway involved in phenylalanine and tyrosine catabolism, I found the article written by Shepartz2 in 1953. Shepartz has shown that hydroquinone inhibits the activity of homogentisic acid oxidase in vitro. This same enzyme has markedly decreased activity in alkaptonuria (Figure). I would like to propose the following hypothesis: Topically applied hydroquinone inhibits the activity of homogentisic acid oxidase in the skin, resulting in the local accumulation of homogentisic acid, which polymerizes to form ochronotic pigment. In effect, this process would mimic the cutaneous manifestation of endogenous ochronosis. This explanation is supported by the observation that hydroquinone-induced exogenous ochronosis is clinically and
Penneys NS. Ochronosislike Pigmentation From Hydroquinone Bleaching Creams. Arch Dermatol. 1985;121(10):1239–1240. doi:10.1001/archderm.1985.01660100019003
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