Diagnostic utility of dermatoscopy in hydroquinone‐induced exogenous ochronosis

Abstract

Exogenous ochronosis is difficult to treat. Dermatologists should be able to differentiate it from melasma and immediately discontinue hydroquinone. Exogenous ochronosis has characteristic features on dermatoscopy which may obviate the need for an invasive procedure of biopsy for its diagnosis.

Exogenous ochronosis masquerading refractory melasma

“…As it progresses to the third papulonodular stage, the ochronotic fibers degenerate and form a colloid milium. Some lesions may form sarcoid-like granulomas surrounding the ochronotic fibers [3]. In contrast, melasma shows a significant increase in the amount of melanin in all epidermal layers which can be confirmed in MassonFontanna stain.…”

“…It was thought that use of high concentrations of hydroquinone above 4% for a long period of time is responsible for development of exogenous ochronosis. However, recent reports of exogenous ochronosis even in patients using hydroquinone in low concentrations (2%) and for periods as short as 3 months are been described [2,3] The other predisposing factors mentioned in literature include Fitzpatrick's System high phototype, lack of sun protection, skin irritation and vigorous friction [7]. Out of the various theories described the most accepted one is Penneys [8] who attributed the hyperpigmentation due to the inhibition of the enzyme homogentisic acid oxidase by hydroquinone.…”

“…This leads to the accumulation of homogentisic acid which further polymerizes to form 'ochre' pigment in the dermis. According to Dogliotte and Leibowitz [9] exogenous ochronosis has three clinical stages, first as initial erythema and mild pigmentary change; second hyperpigmentation, black colloid milia, and atrophy; and third as development of papulonodules [3]. Hydroquinone has been used for treating hypermelanosis, senile lentigo, pigmented areas of vitiligo and melasma.…”

“…Since the treatment is not easy, hence prevention is very important and suggested. The use of lower concentrations of hydroquinone under medical supervision, sun protection and early diagnosis of symptoms clinically are recommended [2,3,7].…”

“…In contrast, exogenous ochronosis presents as gray-brown or blue-black macules, hyperchromic, pinpoint papules in photo-exposed regions in a symmetrical pattern. It can occur secondary to the topical application of hydroquinone, phenol, resorcinol, or even by oral administration of antimalarials [3].…”