Retrospective review of lichen planus pigmentosus (LPP) and ashy dermatosis (AD) – Risk factors, clinicopathologic features, and treatment outcomes

Background: LPP and AD are pigmentary conditions which are closely related on clinical and histopathologic appearance but are treated as separate clinical entities.(1) Treatment of LPP and AD are difficult and there is a lack of studies discussing the clinicopathologic differences, and efficacy of various treatment methods.
Methods: A retrospective medical chart review of all patients who were diagnosed with LPP or AD at a tertiary dermatology clinic from year January 2010 to December 2014 was conducted.
Results: 93 patients were identified. Mean age was 45 +/- 15 years old, with a female preponderance. Median age of onset was 46 +/- 16 years old, with median duration of disease 9 months. The cohort was racially diverse, with a majority of Indian patients (55.9%). Diagnosis was LPP in 43.0% and AD in 24.7% of patients with the remaining having unclear clinical diagnoses with likely AD, either AD or LPP and likely LPP. 44 patients underwent biopsy and histologic features are discussed.
LPP was associated with a predilection to the face and neck, whereas AD was associated with presence in the limbs. Purplish hue was associated with LPP. Both rashes were largely asymptomatic, with an insidious onset, but a preceding rash was more likely to be observed in AD whereas during the course of disease, itch was more likely to be experienced in LPP. Treatment included hydroquinone, topical steroids, tretinoin, protopic, and oral steroid.
1. Vega ME, Waxtein L, Areas R, et al. Ashy dermatosis and lichen planus pigmentosus: a clinicopathologic study of 31 cases. Int J Dermatol. 1992;31(2):90-4

Dr. Hui Mei Cheng