Introduction/Background*Successful management of choriocarcinoma with single-agent methotrexate is documented since 1956. Methotrexate multiday-regimen remains the typical first-line therapy in low-risk Gestational Trophoblastic Neoplasia (GTN). GTN is very sensitive to chemotherapy but evidence on serious adverse events is of low certainty. Stevens-Johnson Syndrome (SJS) is a severe cutaneous adverse reaction with a high mortality rate. This to the best of our knowledge is the second case in the medical literature of SJS following the use of intermediate-dose methotrexate (> 50 to < 500 mg/m2).

Methodology 33-year-old woman noted with rising serum Beta-Human-Chorionic-Gonadotropin (BHCG) level two months after Caesarean delivery of term singleton gestation. BHCG rose from 5160 in June to 68,300 mlU/ml in July. Past medical history significant for genital herpes-simplex-virus infection. Sonogram showed a vascular mass within the endometrial cavity. Subsequently underwent suction dilatation and curettage with pathological diagnosis of choriocarcinoma .Treated as an outpatient with methotrexate 1mg/kg (66mg total dose) by subcutaneous injection daily for five days.

Patient presented with fever, pruritic external genital vesicles and dysphagia two days after fifth methotrexate dose. Vitals were stable. A diffused erythematous maculovesicular rash was noted on face and chest with painful white plaques on oropharyngeal mucosa. She was admitted with a presumptive diagnosis of oropharyngeal thrush , disseminated herpes infection and stomatitis.

Result(s)*Despite antiviral therapy , skin lesions progressed to upper back and vaginal mucosa. Serological and direct fluorescent antibody tests for HSV1 , HSV2 and varicella virus were negative. Dermatology consult reported skin biopsied histopathological findings most compatible with SJS. The following week dysphagia resolved and desquamated lesions were resolving. At discharge BHCG level decreased to 39.7 mIU/ml.

Conclusion*Our case highlights the diagnostic dilemma of a life threatening adverse drug reaction to methotrexate therapy for low risk GTN. Despite being rare, we believe that SJS should be considered in patients presenting with adverse reactions to methotrexate within or outside guideline regimens. Early diagnosis and management of SJS can limit mortality and sequelae and in the case of GTN may involve the selection of an alternative single agent chemotherapy if further treatment is warranted.