Abstract
Four children who had acurate lymphoblastic leukaemia in remission and developed pneumonia were studied. Investigations including electron microscopy and immunofluorescence of lung biopsy material disclosed measles, although there was no clinical evidence of the disease. Despite an identical presentation, two types of illness developed: two children died of giant-cell pneumonia, while the other two developed pneumonia indistinguishable from that associated with methotrexate treatment, recovering when treated with steroids and gammaglobulin. Measles infection is easily overlooked in the absence of rash. The diagnosis may be suggested by clinical and radiological features and confirmed by specific immunofluorescence staining of lung biopsy tissue.