Features and symptoms of Psoriasis
Clinical features. Typical distribution is extensor. The areas commonly affected are the scalp, back of elbows, front of knees and legs and the lower part of the back of the trunk.
The nails, the palms and the soles may also be affected in the average case; but the mucous membranes may be rarely involved.
Clinically, psoriasis exhibits itself as dry, well-defined macules, papules and plaques of erythema with layer of silvery scales. The typical lesions are coin-shaped; by confluence, big plaques of the size of the palm of a hand (or even bigger) or figurate areas may be formed.
When a psoriatic lesion is scratched with the point of a dissecting forceps, a candle-grease-like scale can be repeatedly produced even from the non-scaling lesions. This is called the Candle-grease Sign (Tache de bouge).
The complete removal of a scale produces pin-point bleeding (Auspitz sign). The lesions are slightly raised above the surface of the skin, but there is no indurations.
Psoriasis is normally characterized by the absence of itching, but in tropical countries, patients complain of slight or moderate pruritus which, if accompanied by secondary psychogenic stress and lichenification, is more marked.
Psoriatic lesions may develop along the scratch lines in the active phase; this is called Koebner's phenomenon (other common diseases in which Koebner's phenomenon occurs are warts and lichen planus). The central clearing of the circular lesions produces ringed lesions - Annular psoriasis.
The scalp is involved in almost all cases. It shows thick, scaly papules discretely distributed allover, with intervening areas of normal skin. The lesions are dry, and there is no matting of hair, the latter comes out Straight through the scales. Psoriasis of the scalp never causes loss of hair and baldness.
Nails show three types of lesions:
- separation of the distal portion of the nail from the nail-bed and walls, and
- thickening of the nail, accompanied by the collection of hyperkeratotic debris under the nail.
The face is relatively spared, but lesions may occur along the scalp border ( Corona psoriatica).
The palms of the hands are involved more commonly than the soles of the feet. Lesions consist of well-defined patches of hyperkeratosis and fissures, on erythematous bases. Lesions are bilaterally symmetrical.
Occasionally psoriasis starts on the palms and soles; it may be confined to these areas (Psoriasis inversus).