Although lichen planus manifests with pruritic violaceous lesions and can affect acral skin sites, the histopathologic picture is that of a lichenoid dermatitis, with a bandlike inflammatory infiltrate that abuts the epidermis and is associated with epidermal hyperplasia.
Erythema multiforme usually affects acral sites, but the histologic appearance is characterized by an interface dermatitis without involvement of the deep dermal adnexal structures or perivascular areas.
Clinically, one could consider contact dermatitis in a case in which a rash cyclically appears. However, the histologic features of contact dermatitis typically show a spongiotic dermatitis, and the deep perivascular and periadnexal areas are unaffected.
Although necrolytic acral erythema occurs on acral sites, the lesions are characterized histologically by the presence of pallor of the epidermis, focal necrosis, spongiosis, and parakeratosis.
Pernio, or chilblains, is characterized by a superficial and deep perivascular and perieccrine inflammatory infiltrate that usually is seen in skin biopsy specimens of acral skin.