Lichen simplex chronicus

Lichen simplex chronicus (prurigo nodularis) is a secondary skin disease caused by chronic scratching. The primary change is any itching with an urge to scratch. Chronic mechanical irritation of the skin gradually leads to thickening and other changes (lichenification).

Clinical picture
The lesions are usually scaly, thickened, with moderate erythema and relatively well circumscribed. Secondary changes (lichenification, excoriation and crusting) are common. A raised itchy nodule is usually referred to as prurigo nodularis.

Histopathological picture
The main histopathological finding is distinct psoriatiform acanthosis. Hyperkeratosis is common, sometimes massive. Hyperkeratotic changes can have the character of orthokeratosis or parakeratosis. Spongiosis is usually only minimal and focal, and may be completely absent. Beneath the epidermis there can be varying degrees of fibrosis.