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.