Erythema multiforme associated with prophylactic use of phenytoin during cranial radiation therapy

A case of erythema multiforme associated with prophylactic use of phenytoin during cranial radiation therapy is reported.

A 60-year-old woman with intraductal adenocarcinoma of the breast and cerebral metastasis who had an implanted central venous catheter arrived at the hospital for the treatment of cerebral metastasis. She underwent whole brain irradiation and was given a total dose of 3750 cGy over 15 fractional doses spaced over three weeks. At the beginning of cranial radiation therapy, prophylactic oral ranitidine, oral dexamethasone, and oral phenytoin were initiated to prevent seizures. After 30 days of continuous prophylactic phenytoin and cranial radiation therapy, the patient developed an episode of coughing with yellow sputum, mucositis, and a minor skin reaction that was diagnosed in the emergency department as radiotherapy-associated lesions. After 2 days, the patient returned to the hospital with severe mucositis and an erythematous macular eruption on the scalp and auricular region within the radiation field. These were believed to be due to the radiation therapy, and the patient was subsequently hospitalized. The eruption dramatically extended over the next day, with itching micropapular urticarial lesions over large areas of the face, trunk, and genital region. The condition had worsened by the next day, with erythematous eruptions on the whole body (including the extremities), skin detachment, and vesicular lesions on the eyelids. The patient was then diagnosed toxic epidermal necrolysis.

A patient with intraductal adenocarcinoma of the breast and cerebral metastasis developed erythema multiforme after receiving concurrent phenytoin and radiation therapy.