Asynchronous development of two monoclonal proteins (IgM lambda and delta 1 chains) in a patient with abdominal lymphoma.

An IgM paraprotein was detected in a patient with abdominal lymphoma. Due to some doubts about the malignant nature of the situation, no cytostatic drugs were administered. When seen two years later the patient had considerably deteriorated in clinical status, with evidence of extra-abdominal involvement. At this time he presented a second paraprotein of low of molecular weight (74,000 to 80,000), consisting of two covalently linked delta1-chain fragments.