Lichen planus-like atopic dermatitis: expanding the differential diagnosis of spongiotic dermatitis.

Spongiotic dermatitis represents a commonly encountered histopathological pattern seen by dermatopathologists. The differential diagnosis of lymphocyte predominant acute spongiotic dermatitis typically entails atopic dermatitis (AD), contact dermatitis, nummular dermatitis, pityriasis rosea and seborrheic dermatitis. Recently, our group has characterized a distinct subtype of spongiotic dermatitis occurring exclusively in heavily pigmented patients. Clinically, lesions of this subtype are nearly indistinguishable from lichen planus. However, the histology is contradistinctive to classic lichen planus. The purpose of this report is to raise awareness among dermatopathologists of this variant as a possible diagnosis in spongiotic dermatitis specimens submitted as lichen planus.