ABSTRACT
Lichen planus pigmentosus (LPP) was first described by Bhutani et al. LPP is a rare entity most frequently described in India, Latin America, the Middle East, Korea, Japan, and the Mediterranean region. Dark-skinned individuals are more commonly affected. No clear sex predilection exists. LPP has its onset usually during the third or fourth decade of life. The nature of this disorder remains enigmatic. However, a number of etiological factors, like ingestion of ammonium nitrate, nematode infestation, radiographic contrast media, cobalt allergy, contact allergens, and chlorothalonil exposure among banana farm workers, have been implicated. Activated cytotoxic T cells cause basal layer damage, keratinocyte apoptosis, and subsequent pigment incontinence. The diagnosis is based on a combination of clinical and histopathological features. The ash-gray to dark brown macules and patches of LPP should be distinguished from numerous acquired pigmentary disorders. Various treatments, such as sun protection, topical corticosteroids, hydroquinone, and chloroquine, have been used with little benefit.
