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.
Comment / Explanation
Localized keratosis with excessive scales such as cutaneous horn.
Lichenification (thickened, scaly epidermis).
Inflammation: psoriasis, atopic dermatitis.
Ichthyosis, xeroderma (dry skin), keratoderma.
Excessive hyperproliferation of epidermal layers, loss of adhesion of keratinocytes.