Exogenous Ochronosis

Abstract

Exogenous ochronosis (EO) is a cutaneous disorder characterized by blue-black pigmentation resulting as a complication of long-term application of skin-lightening creams containing hydroquinone but may also occur due to topical contact with phenol or resorcinol in dark-skinned individuals. It can also occur following the use of systemic antimalarials such as quinine. EO is clinically and histologically similar to its endogenous counterpart viz., alkaptonuria, which, however, exhibits systemic effects and is an inherited disorder. Dermoscopy and in vivo skin reflectance confocal microscopy are noninvasive in vivo diagnostic tools. It is very difficult to treat EO, a cosmetically disfiguring and troubling disorder with disappointing treatment options.

Dermoscopy of melasma

“…Thus, dermoscopy, being noninvasive, is very useful in differentiating melasma from its clinical differentials, especially EO, and may also aid in choosing the appropriate biopsy site in suspected cases [ Table 1 ]. [ 1 2 ]…”

“…Except for the description in the study by Yalamanchili et al .,[ 3 ] other dermoscopic features of melasma have mostly been mentioned as a comparison against other facial melanosis (to rule out melasma). [ 1 2 ] A light-to-dark brown background and brown granules and globules with perifollicular sparing have been uniformly described. [ 1 2 3 4 5 ] The basic pattern may be reticular or pseudoreticular (more common in deeper melasma).…”

A case report on hydroquinone induced exogenous ochronosis

“…Due to lack of skin biopsy findings the diagnosis may not be confirmed, so the incidence of this condition is more than that of reflected in the literature. 10 Exogenous ochronosis is an uncommon adverse reaction associated with the hydroquinone, with global data pertaining to number of individual case safety reports reported till date that is less than ten from the reported events to the WHO-UMC database. 11 Although it is believed that application of high concentrations of hydroquinone after applying for a prolonged period causes exogenous ochronosis.…”

Ochronotic pigmentation is caused by homogentisic acid and is the key event in alkaptonuria leading to the destructive consequences of the disease—A review

“…Ochronosis‐like processes have also been described in non‐AKU states and termed pseudo‐ochronosis or exogenous ochronosis (as opposed to endogenous ochronosis in AKU). Exogenous ochronosis has been the subject of previous reviews and will not be discussed further here …”