Lichen planus pigmentosus and ashy dermatosis: a clinical, dermoscopic and histopathological comparison.

Background Lichen planus pigmentosus (LPP) and ashy dermatosis (AD) are disorders of hyperpigmentation and differentiation between two can be difficult. They can be close mimickers. Earlier they were considered the same entity but over time various authors enlisted a few clinical and histopathological differences between the two. In this review, we would add the additional dermoscopic differences and review the clinical and histopathological differences between these two confusing entities. Aim To differentiate between lichen planus pigmentosus and ashy dermatosis on the basis of clinical, dermoscopic and histopathological features. Methods We selected ten patients of newly diagnosed lichen planus pigmentosus and ten of ashy dermatosis presenting to dermatology OPD. Clinical examination, dermoscopy and punch biopsy were performed in each case. Results Out of the 20 patients who were included in this study, 10 were diagnosed with lichen planus pigmentosus and 10 with ashy dermatosis. 80% patients presented with pruritus in LPP and all patients were asymptomatic in AD. In LPP, most common pattern was diffuse where on dermoscopic examination, granules were seen arranged in a hem like pattern. In AD, pigment was seen present in a curvilinear fashion. Conclusion Differentiation between lichen planus pigmentosus and ashy dermatosis can be a daunting task. Dermoscopy is a useful and non-invasive modality that can be of immense help. [ABSTRACT FROM AUTHOR]