CD40LG and erythema multiforme: Possible case: EMProbable case: EM and a history of tick bites or another clinical manifestation (except neurologic) with a history of EMConfirmed case: one of the clinical manifestations (except neurologic) that is also laboratory confirmed by either specific IgM and IgG antibodies in serum or CSF by IFA, EIA, WB; isolation of the bacterium or its DNA