[Hypoglycemia and multiple myeloma]

We report the case of a 78-year-old patient with recurrent attacks of severe fasting and late postprandial hypoglycemia, whose plasma showed highly elevated concentrations of immunoreactive insulin evidenced by high titers of spontaneous insulin and proinsulin-binding antibodies. Insulin autoimmune syndrome was diagnosed. Further investigations revealed a multiple myeloma of the kappa-light chain type. The monoclonal insulin-binding antibodies were characterized as IgG2-subclass and were identical with the paraprotein, thereby confirming that the insulin-binding antibodies were in fact produced by the myeloma. Together with initial symptomatic treatment, plasmapheresis was performed repeatedly to reduce the antibody pool. Subsequently octreotide therapy proved successful. The underlying myeloma was treated by chemotherapy.