Erythema annulare centrifugum associated with ascariasis.

Erythema annulare centrifugum (EAC) is a figurate erythema that has been associated with man diverse entities. A case of EAC was related to infestation by the nematode, Ascaris lumbricoides. A careful examination of the patient did not define an immunologic basis for EAC. Results of lymphocyte stimulation tests of the patient showed an immune response to A lumbricoides extracts but not to A suum extracts. This finding is of practical importance, since most laboratoires use A suum extracts in routine skin and serologic tests for human ascariasis.