Lichen planus pigmentosus: The controversial consensus

Abstract

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.

Histological evaluation of acquired dermal macular hyperpigmentation

“…Lack of consensus exists regarding their classification and evaluation of individual patient. [1234]…”

“…[1] Others have described sparse inflammation and mild basal cell degeneration in erythema dyschromicum perstans. [4]…”

“…[123] Consensus regarding whether all these represent different stages of same disease process or different entities is lacking. [4] Degos et al in 1978 described idiopathic macular eruptive pigmentation (IMEP) characterized by pigmented macules over neck, trunk, and limbs in children and adolescents that resolved spontaneously. [5]…”

Dermoscopy in assisting the recognition of ashy dermatosis

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Key messages Although clinical recognition of AD is often a straightforward task based on the detection of a typical bluish hue and elevated erythematous margins, sometimes such clues may be scarcely visible, and the condition may be mistaken for other similar dermatoses, especially lichen planus pigmentosus ( Fig 1 , B ), 1 with consequent inappropriate/ineffective therapeutic management. According to our case, dermoscopy may be used as a supportive tool in the diagnosis of AD by highlighting gray-bluish small dots over a bluish background, which correspond to melanophages/melanin deposits in deeper dermis (Tyndall effect).

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“…Such a dermoscopic picture is quite different from that of lichen planus pigmentosus, as this typically displays larger dots/globules having a brownish shade 2 ( Fig 2 , B ) because melanophages/melanin deposits are located more superficially in the dermis as a result of dermoepidermal junction damage caused by the peculiar lichenoid inflammation located just below the epidermis ( Fig 3 , B ), which is classically absent in AD. 1 …”