Dyshidrotic Dermatitis

Dyshidrotic dermatitis is characterized by recurrent, severely pruritic, deep-seated vesicles that classically involve the lateral aspects of the fingers and, in some cases, the toes. Episodes may be precipitated by infections, "id" reactions, contact reactions, and emotional stress. In chronic cases, there may be more extensive involvement of the palms and soles. Although the eruption develops acutely, it may become chronic with erythema, lichenification, and fissuring. Secondary impetiginization is common.

Histopathology.

 Spongiosis and intraepidermal vesiculation occur in acute lesions . There is a superficial perivascular Iymphohistiocytic infiltrate with exocytosis of lymphocytes into spongiotic zones. The infiltration is usually mild. In acute lesions, the compact, thickened stratum corneum of acral skin remains intact, and the epidermal thickness is normal. With chronicity, spongiosis diminishes; acanthosis and parakeratosis predominate with variable crusting. Difficulty in differential diagnosis with pustular psoriasis may occur because of the formation of vesiculopustules in older lesions. A periodic acid-Schiff (PAS) stain should always be performed on vesicular lesions of the palms and soles, because tinea manus/pedis may mimic dyshidrotic dermatitis histologically.