Lichen Planus Pigmentosus Inversus: A Case Report of a Man Presenting With a Pigmented Lichenoid Axillary Inverse Dermatosis (PLAID).

Lichen planus pigmentosus is an uncommon subtype of lichen planus and lichen planus pigmentosus inversus is a rare variant of lichen planus pigmentosus. Lichen planus pigmentosus inversus typically presents as hyperpigmented patches or plaques, particularly in the intertriginous areas such as the axillae, the groin and inguinal folds, and in the submammary region. In some patients with lichen planus pigmentosus inversus, the condition can present as a pigmented lichenoid axillary inverse dermatosis (PLAID) when the lesions are in the axillae. A 49-year-old Hispanic man who had hyperlipidemia and diabetes mellitus developed lichen planus pigmentosus inversus and presented with a PLAID. Skin biopsies established the diagnosis of lichen planus pigmentosus inversus. The clinical differential diagnosis of lichen planus pigmentosus inversus includes inherited disorders, primary cutaneous dermatoses, acquired dyschromias, and reactions to topical or systemic medications. Friction in intertriginous areas has been related to the development of lichen planus pigmentosus inversus. Factors that can precipitate lichen planus pigmentosus inversus include not only topical exposure to almond oil, amala oil, cold and cosmetic creams, henna, and paraphenyldiamine but also either topical contact or consumption of mustard oil and nickel. Lichen planus pigmentosus inversus can be associated with autoimmune conditions (hypothyroidism), endocrinopathies (diabetes mellitus), and hyperlipidemia. The dyschromia found in patients with lichen planus pigmentosus inversus is frequently refractory to treatment. Initial management includes removal of potential disease triggers such as eliminating tight clothing to stop friction with the adjacent skin. Topical corticosteroids do not result in improvement; however, topical calcineurin inhibitors such as tacrolimus have been reported to be efficacious. In conclusion, inverse lichen planus and lichen planus pigmentosus inversus can present with a PLAID; whereas topical corticosteroids may be helpful to resolve inverse lichen planus lesions, topical tacrolimus may be useful to improve the dyschromia in lichen planus pigmentosus inversus.