Prolonged course of illness in a child with malignant lymphoma mimicking sarcoidosis.

We describe a case of malignant lymphoma mimicking the rheumatic presentation of sarcoidosis in an adolescent with a 3-year history of febrile illness. Final diagnosis was established by tissue biopsy after multiple studies failed to provide histological evidence of granulomas consistent with sarcoidosis. We discuss the limited diagnostic specificity of serum angiotensin converting enzyme in sarcoidosis and emphasize the need for aggressive diagnostic evaluation of a patient whose clinical presentation is not fully explained by a known rheumatologic illness.