Phenytoin-carbamazepine cross-sensitivity

Erythema multiforme associated with phenytoin and cranial radiation therapy: A report of three patients and review of the literature

BACKGROUND

Intracranial malignancies (primary and metastatic) are often complicated by seizure activity. Phenytoin (Dilantin) is typically employed as prophylactic anticonvulsant in this setting. Uncommonly, erythema multiforme (EM) can develop in such patients at the port site during or soon after cranial radiation and can rapidly progress to EM major. Herein, in addition to a comprehensive literature review of this entity, three additional patients are presented. The acronym 'EMPACT' is suggested (E: erythema; M: multiforme; associated with P: phenytoin; A: and; C: cranial, radiation; T: therapy) to best describe this disorder.

METHODS

An extensive review of the English medical literature through the National Library of Medicine (PUBMED) was performed to identify patients who had received or continued to receive radiation therapy while on phenytoin. A total of 24 patients were identified and clinical information of varying detail was available in all cases. Clinical and histological information on three additional patients seen at two institutions (Rochester Methodist Hospital, Rochester, MN, and Fairview-University Medical Center, Minneapolis, MN) by the authors were also compiled.

RESULTS

The mean age was 44 years (range: 23-67) and no sexual predisposition was noted. All patients had taken phenytoin for variable time periods (range 16-80 days; mean: 40) and were on the medication when the skin lesions first appeared. These lesions developed within the port site during the radiation treatments (11 cases) or soon after (nine cases) its completion (mean: 16 days; range: 2-35). Subsequent disease evolution to EM major occurred in all cases (Stevens-Johnsons syndrome developed in 73% of patients). No relationship was identified between the extent and the severity of the skin lesions with the phenytoin and radiation dosages and with the histologic type and origin of the intracranial malignancy. None of the patients demonstrated the requisite features of the 'Dilantin hypersensitivity syndrome'. Although, a systemic steroid taper was employed in 10 out of the 14 patients before the development of the skin lesions, the subsequent progression of the skin lesions was not influenced by the use of systemic steroid therapy. Complete recovery occurred in all but two patients typically within 1-8 weeks of discontinuation of phenytoin.

CONCLUSIONS

The need for prophylactic anticonvulsant therapy especially utilizing phenytoin in patients undergoing cranial radiation therapy should be assessed on a case by case basis. If anticonvulsants are employed, then they must be administered with caution, and all cutaneous reactions developing subsequently within the radiation site must be promptly evaluated with a high index of suspicion for erythema multiforme.

Carbamazepine hypersensitivity syndrome: report of 4 cases and review of the literature

We report 4 patients who developed a severe systemic hypersensitivity reaction when taking carbamazepine, To prove hypersensitivity to carbamazepine, we performed patch tests and in vitro lymphocyte transformation tests. Patch tests were uniformly and strongly positive in patients and negative in controls. Lymphocyte transformation tests were positive in 3 of 4 patients. We reviewed the literature on reports of carbamazepine-induced pseudolymphoma and other severe systemic hypersensitivity reactions. Considering the many common clinical, biochemical, and pathologic characteristics, we propose to group these reactions under the term "carbamazepine hypersensitivity syndrome." The syndrome is characterized by the development of fever, rash, and lymphadenopathy between 1 week and 3 months after the introduction of carbamazepine. A variety of other target organs may be involved, including the liver, kidneys, and lungs. The carbamazepine hypersensitivity syndrome is a clinical diagnosis. Patch tests and lymphocyte transformation tests are valuable tools to confirm the diagnosis, but are reliable only after all signs subside. Similar syndromes have been described with the other aromatic anticonvulsants (phenytoin, the other hydantoins, and phenobarbital), and there is evidence of a cross-reaction between carbamazepine and phenytoin. It is unknown whether the carbamazepine hypersensitivity syndrome should be considered a premalignant state, with an increased risk for the development of malignant lymphoma.