A 41-year-old man with breast cancer and dyspnoea: an exceptional complication in an uncommon disease.

A case of advanced breast cancer in a young male, who developed progressive dyspnoea a few months after treatment with chemotherapy is described. The clinical and radiological picture, supported by lung function testing, finally revealed the tentative diagnosis of bronchiolitis obliterans, most probably due to cyclophosphamide, one of the drugs used in the cytotoxic therapy. Two distinct clinical patterns of pulmonary toxicity associated with cyclophosphamide are reviewed: the acute pneumonitis that occurs early in the course of treatment; and the chronic, progressive, fibrotic process, of which bronchiolitis obliterans is an uncommon presentation. Cyclophosphamide pulmonary toxicity is primarily a clinical diagnosis and the typical features are discussed. Early-onset pneumonitis due to cyclophosphamide is a reversible process with a good prognosis. On the other hand, late-onset pneumonitis or lung fibrosis is essentially irreversible and follows a chronically progressive course over months to years. It almost inevitably leads to terminal respiratory failure.