A New Case of Mu Heavy Chain Disease: Clinical and Immunochemical Studies

A new case of mu heavy chain disease is described. The patient, a 48-yr-old Italian housewife, suffered from chronic lymphocytic leukemia of 3 yr duration with anemia and hepatosplenomegaly, but no peripheral lymph node enlargement. Serum protein studies disclosed a small M component with gamma-1 mobility ascribable to free kappa chains, hypogammaglobulinemia, and mu chain fragments with abnormally anodic mobility. Appreciable amounts of kappa chains were also detected in the urine. The mu chain disease protein had a molecular weight of approximately 54,000 and a heterogeneous NH₂ terminus, alanine being the main identifiable residue. The NH₂ terminal of the kappa chain was glutamic acid. No J chain was detected by polyacrylamide electrophoresis of the partially reduced and alkylated mu chain disease protein.