Exogenous Ochronosis: Clinicopathological Correlation in Indian Patients and the Practical Applicability of the Dogliotti and Phillips Classification Systems.

Exogenous ochronosis (EO) results as a complication of long-term usage of skin lightening creams containing hydroquinone or other bleaching agents. Duration of use and concentration of hydroquinone in the product are noted to be key factors that decide the occurrence of EO. With more cases being reported globally, current classification systems lack practical applicability and may not be adequate for detecting early cases. Dermoscopy and clinicopathological correlation are very important for early diagnosis of EO to avoid undue overuse of hydroquinone leading to further deterioration of pigmentation. We report a series of six patients in one year with EO with the minimum duration of use of hydroquinone being three months to the development of ochronosis. The most common strength of hydroquinone used was 2%, documented in 5/6 cases. Three out of six patients (50%) had discordant findings according to the Dogliotti classification, while four out of six patients (66.7%) had discordant findings according to the Phillips classification. Our findings suggest that EO can occur with a shorter duration of hydroquinone use, even at lower percentage strengths. We propose that it may be more useful to accept the clinical presentation supported by dermoscopic features as adequate actionable findings, consider all the histopathological stages as warning signs of ochronosis or impending ochronosis, and terminate the use of hydroquinone in such patients.