Abstract
The case of a middle aged woman who presented with fibrosing alveolitis, in her mid-forties, followed by a sicca syndrome and who subsequently developed a pulmonary lymphoma (B cell) while receiving azathioprine therapy is recorded. Of interest was the absence of polyclonal B cell activation, e.g., production of rheumatoid factor, hypergammaglobulinaemia, high titre antinuclear antibodies or antibodies to extractable nuclear antigens (ENA) during most of her illness. Persistently raised IgM levels and low IgA levels were demonstrated. The relevance of azathioprine to development of the lymphoma is discussed.