Nonimmediate allergic reactions induced by Mesna.

Mesna (2-mercaptoethane sulfonate Na), a drug that alleviates cyclophosphamide (CYC)-induced hemorrhagic cystitis, is frequently used to treat cancer and collagen diseases. A 33-year-old woman presented with high fever during CYC-based induction therapy for systemic lupus erythematosus. Her final diagnosis was mesna-induced drug hypersensitivity. Although mesna is widely used, allergic reactions are rare. This may be because of misdiagnosis as a primary disease flare-up, infection, or CYC-induced hypersensitivity reaction, which are commonly reported. Thus, accurate diagnosis is important for completion of the CYC-based regimen.