A patient presents with scarring Alopecia, thinned nails, hypopigmented macular lesions over trunk and oral mucosa. The diagnosis is :

Lichen planus (LP) is a papulosquamous disorder that may affect the skin, scalp, nails, and mucous membranes. The primary cutaneous lesions are pruritic, polygonal, flat-topped, violaceous papules. Close examination of the surface of these papules often reveals a network of gray lines (Wickham's striae). The skin lesions may occur anywhere but have a predilection for the wrists, shins, lower back, and genitalia. Involvement of the scalp, lichen planopilaris, may lead to scarring alopecia, and nail involvement may lead to permanent deformity or loss of fingernails and toenails. LP commonly involves mucous membranes, paicularly the buccal mucosa, where it can present a spectrum of disease from a mild, white, reticulate eruption of the mucosa, to a severe, erosive stomatitis. Erosive stomatitis may persist for years and may be linked to an increased risk of oral squamous cell carcinoma. Ref: Harrison's Internal Medicine;Pa 2. Cardinal Manifestations and Presentation of Diseases ;Section 9. Alterations in the Skin ;Chapter 53. Eczema, Psoriasis, Cutaneous Infections, Acne, and Other Common Skin Disorders-Eczema and Dermatitis