Erythema multiforme and Stevens-Johnson syndrome in patients receiving cranial irradiation and phenytoin.

In 15 months we encountered eight patients with intracranial tumors who developed erythema multiforme (EM) or erythema multiforme bullosa (Stevens-Johnson syndrome). All occurred shortly after use of phenytoin (DPH) and brain radiation therapy (WBRT). The clinical picture differed from the classic form of EM in that the erythema began on the scalp and spread to the extremities, progressing in three cases to extensive bullous formation. There were no cases of EM among patients who received either DPH or radiotherapy alone. The combination of DPH, WBRT, and tapering of steroids seems to predispose to EM. The pathogenesis of the disorder is probably immunologic. In the absence of seizures, anticonvulsants should not be given routinely to patients with brain tumors. When anticonvulsants are necessary in patients scheduled for WBRT, DPH may not be the drug of choice.