Annular psoriasiform eruption with lymphocytic infiltration of the epidermis: a variant of acute psoriasis?

Disseminated annular psoriasiform lesions developed over a period of 2 months in a 48-year-old man with no preceding psoriatic history of drug intake, being accompanied by general dullness and arthralgia. Etretinate was effective for both skin eruption and arthralgia; only the latter recurred on its cessation 5 months later. However, histologic features examined by serial sections totally lacked those of pustular psoriasis; there were no neutrophils in the epidermis where massive T lymphocyte infiltration existed instead, in a fashion similar to that of early psoriatic lesions. We differentiated this peculiar annular psoriasiform eruption from the annular erythematous lesions noted in pityriasis rosea, erythema annulare centrifugum, subacute cutaneous lupus erythematosus, annular erythema associated with Sjögren's syndrome and erythema chronicum migrans. It is our speculation that this dermatosis represents a variant of acute psoriasis, rather than annular pustular psoriasis. The histopathologic and immunohistologic findings suggest ongoing cellular immune responses in these lesions where some unknown inhibitory mechanisms might be operative against further production of neutrophil chemotactic factors that usually takes place in psoriatic lesions.