[Immunochemical properties of free mu-chain protein in a patient with mu-heavy chain disease].

We report a case of mu-heavy chain disease. A 56-year-old woman presented with anemia and hemorrhagic diathesis. The serum of the patient was found to have free mu-heavy chain. The patient also had a kappa type-Bence Jones protein in serum and urine. Immunoelectrophoresis showed an abnormal precipitin line in the alpha 2-globulin region which reacted with antiserum to mu-chain but not with antiserum for light chains. The molecular weight of the monomer of the patient's mu-heavy chain protein was approximately 67,000 daltons less than that of the normal mu-heavy chain protein.