Plaques with silvery scales over back are a characteristic feature of lesion of?

Ans is 'b' i.e. Psoriasis * The typical psoriatic lesion is nummular round plaque which has following characteristic features: -a) Well definedb) Profuse, silvery white, powdery scales (Candle drop scales) - Loosely adherent and easily drops.c) Bright red erythematous base.d) Plaque is often surrounded by a hypopigmented halo - Ring of Womoff.Other clinical features of Psoriasis (psoriasis vulgaris)* Lesions are mildly pruritic or non-pruritic.* Psoriatic lesions may develop at the site of trauma - Koebner's or isomorphic phenomenon.* When a psoriatic lesion is scratched with the point of a dissecting forceps, a candle-grease like seal can be repeatedly produced even from the non-scaling lesions - Candle-grease sign.Sites of predilection* Lesions are bilaterally symmetrical. Psoriasis favours extensors areas pressure points (knee, elbow), scalp, lumbosacral area and back. Face involvement is uncommon, though scalp lesions can extend on forehead. Mucosal surfaces (oral, genital) are not involved. Scalp involvement does not cause alopecia, usually