Darkness defines lichen planus pigmentosus (LPP) – lesional morphology, the patient’s mood about their appearance, and our ability to understand or treat it. Both patient and physician are literally in the dark.
The following abstract by Ghosh and Coondoo (1) is an excellent summation of the current concepts of LPP:
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.
Lichen planus pigmentosus inversus (LPPI), as noted above, involves intertriginous regions, notably the axillae and inguinal region. In a review of ten cases of LPPI that were clinically suspected and histologically confirmed, Mohamed et al observed that the mean age of patients was 62.4 years old. Eight patients were women and two were men. Main folds involved were the axillae and groin. All patients were treated with topical steroids without success (2).
Personally, I prefer the term “lichenoid melanodermatitis” as it is an umbrella term that recognizes that this is reaction pattern that includes a differential diagnosis, with the understanding that we may not know the precise etiology in any particular case. Erythema dyschromicum perstans (EDP), fixed drug eruption, heavy metal exposure, macular amyloidosis, tar melanosis, frictional melanosis, berloque dermatitis, pigmented cosmetic dermatitis (Reihl’s melanosis), idiopathic eruptive macular pigmentation, mastocytosis, lupus, and postinflammatory hyperpigmentation, all need to be considered.
Treating LPP or LPPI is notoriously frustrating, showing minimal improvement with topical steroids, calcineurin inhibitors, topical retinoids, azeleic acid, chemical peels or lasers. Sun avoidance and photoprotection is a must for LPP. Low-dose isotretinoin (0.3 mg/kg) combined with sunscreens, may be a promising treatment modality in stabilizing and decreasing the pigmentation in LPP, particularly in early and limited disease (3). Indeed, when I reviewed this paper, the changes from acute lichenoid inflammation to those consistent with post-inflammatory hyperpigmentation were evident. Before administering oral isotretinoin for LPP or LPPI, I would recommend performing a biopsy first, and only consider prescribing it if vacuolar alteration, Civatte bodies, or lichenoid inflammation are present.
Mechanistically, diagnostically, and therapeutically, much more light needs to be shed upon the LPP/LPPI world. A brighter future awaits such advances.
- Ghosh A, Coondoo A. Lichen planus pigmentosus: The controvery continues. Indian J Dermatol 2016; 61: 482-6.
- Mohamed M, et al. Lichen planus pigmentosus inversus: A series of 10 Tunisian patients. Int J Dermatol 2016; 55: 1088-91.
- Muthu SK, et al. Low-dose isotretinoin therapy in lichen planus pigmentosus: An open-label non-randomized prospective pilot study. Int J Dermatol 2016; 55: 1048-54.