[A case of IgG4-lambda type monoclonal immunoglobulin that interfered with determinations for albumin, direct bilirubin and iron in serum].

We report a human IgG4-lambda type M-protein that reacts with reagents of albumin, direct bilirubin and iron. Blood chemistry findings by an automated analyzer were: total protein 8.8 g/dl; albumin(ALB) 9.2 g/dl; direct bilirubin(D-Bil) -6.2 mg/dl; and iron(Fe) 25 micrograms/dl. The white precipitates were formed by the interaction of the patient's serum with reagents of ALB, D-Bil, and Fe. Immunofixation electrophoresis revealed that these precipitates were the IgG4-lambda type M-protein. Western blotting analysis showed that the IgG4 molecules were composed of two 55 kDa gamma 4 chains and two 24 kDa lambda chains.