Lichen planus (Q43917)

Lichen planus is an inflammatory disease of skin and mucous membranes characterised by intense inflammation at the interface between epidermis/epithelium and dermis/corium. Its clinical manifestations vary according to how acutely it develops and to where it attacks. On the skin it typically presents as a symmetrical eruption of itchy, flat-topped pink or purple papules or plaques. Involvement of the scalp or nail matrix can produce permanent loss of hair or nails respectively. Although mucous membrane involvement can be asymptomatic, it can cause significant pain and distress, particularly when it is erosive.