Lichen planus pigmentosus: The controversial consensus

A pigmented variant of lichen planus (LP) was first reported from India in 1974 by Bhutani et al. who coined the term LP pigmentosus (LPP) to give a descriptive nomenclature to it. LP has a number of variants, one of which is LPP. This disease has also later been reported from the Middle East, Latin America, Korea, and Japan, especially in people with darker skin. It has an insidious onset. Initially, small, black or brown macules appear on sun-exposed areas. They later merge to form large hyperpigmented patches. The disease principally affects the sun-exposed areas of the body such as the face, trunk, and upper extremities. The oral mucosa may rarely be involved. However, the palms, soles, and nails are not affected. Histologically, the epidermis is atrophic along with vacuolar degeneration of basal cell layer. The dermis exhibits incontinence of pigment with scattered melanophages and a sparse follicular or perivascular infiltrate. There is a considerable similarity in histopathological findings between LPP and erythema dyschromicum perstans. However, there are immunologic and clinical differences between the two. These observations have led to a controversy regarding the identity of the two entities. While some dermatologists consider them to be the same, others have opined that the two should be considered as distinctly different diseases. A number of associations such as hepatitis C virus infection, frontal fibrosing alopecia, acrokeratosis of Bazex and nephrotic syndrome have been reported with LPP. A rare variant, LPP inversus, with similar clinical and histopathological findings was reported in 2001. As opposed to LPP, this variant occurs in covered intertriginous locations such as groins and axillae and mostly affects white-skinned persons.