2.1 Scales

Scales.

Excessive thickening of stratum corneum with desquamation.

Fine scales (pityriasiform) to coarse (psoriasis).

Color: white, gray, yellow.

Size: mm to cm.

Desquamation refers to diffuse shedding of scales. Special form: collerette with the scaling at the border of the lesion.

May appear anywhere on body surface: when localized often favours the palms and soles; may be generalized as in ichthyosis.

May develop erosions or crusts. Associated with papules, pustules and plaques.

Localized keratosis with excessive scales such as cutaneous horn.

 Lichenification (thickened, scaly epidermis).

 Palmoplantar keratoderma.

Infection: tinea.

Inflammation: psoriasis, atopic dermatitis.

Ichthyosis, xeroderma (dry skin), keratoderma.

Excessive hyperproliferation of epidermal layers, loss of adhesion of keratinocytes.