Endogenous ochronosis presenting as recalcitrant facial hyperpigmentation aggravated with prolonged use of topical hydroquinone 2%

Abstract

Ochronosis is an uncommon condition characterized by the deposition of an ochre-colored pigment within the skin, cartilage, and other connective tissues [1]. There are two types of ochronosis: endogenous and exogenous. Alkaptonuria (endogenous ochronosis), is a rare metabolic disorder characterized by a triad of homogentisic aciduria, cutaneous hyperpigmentation, and arthropathy. It is due to the deficiency of the enzyme homogentisic acid oxidase, which catalyzes the conversion of homogentisic acid to maleylacetoacetic acid in the catabolism of tyrosine. Exogenous ochronosis is a cutaneous disorder characterized by the bluish-black hyperpigmentation on the skin due to chronic use of chemical preparation and oral administration of a specific medication [2]. We present an overlap case of exogenous and endogenous ochronosis.