Context

Auto-antibodies to insulin have been described to cause spontaneous hypoglycemia in non-diabetic subjects. There have been occasional reports of spontaneous hypoglycemia due to monoclonal anti-insulin antibodies. We present the first report of a patient with an IgA- myeloma in whom frequent hypoglycemia resulted from the ability of the monoclonal IgA- to bind insulin.

Objective

To describe the occurrence of profound hypoglycemia in a patient with IgA- myeloma, to biochemically characterise the nature of the IgA:insulin complex present and to place this case in the context of the published literature on hypoglycemia resulting from autoantibodies to insulin

Design

Case Study

Patients

A single case of profound hypoglycemia associated with IgA- myeloma

Intervention

None

Main Outcome measure

Case Study

Results

Polyethylene Glycol precipitation and Gel filtration chromatography were used to demonstrate high molecular weight insulin immunoreactivity in the patient's plasma. This was characterised as an Insulin binding IgA- paraprotein present at 4200mg/dL (42g/L) with a relatively high insulin dissociation constant of 0.32 µM/L using radio-labelled insulin binding studies.

Conclusions

We present the first case of hypoglycemia due to IgA binding insulin antibodies in a patient with an IgA- paraprotein myeloma. The hypoglycemia was associated with high plasma insulin levels and relatively low C-peptide levels. A plausible mechanism for the hypoglycemia is the delayed clearance of insulin. This case broadens the spectrum of monoclonal gammopathies that have been associated with anti-insulin reactivity and spontaneous hypoglycemia.