低血糖昏睡を示したインスリン自己免疫症候群の1例

抄録

A case of hypoglycemia with auto-antibody to insulin and characteristics of the antibody were reported.
A 65-year-old female was admitted to our hospital because of unconciousness early in the morning. Her blood glucose values at the attacks were 16 to 19 mg/dl and the attacks were relieved by glucose injection. Her OGTT showed a delayed curve, but the IVGTT showed a normal K value (2.77).
Despite of no history of insulin injection, insulin antibody was demonstrated in the serum by means of ethanol precipitation, paper chromatography, gel filtration and dextran-coated-charcoal procedure. Total immunoreactive insulin extracted from the serum was 22, 200μU/ml. As the celiac angiography suggested the presence of a tumor in the pancreas, the operation was performed under the diagnosis of insulinoma with insulin antibody. The laparotomy disclosed, however, no tumor in the pancreas and 95% distal resection of the pancreas was made. The histological examination showed a slight decrease of the Langerhans' islets, but no pathological changes were found.Insulin content of the pancreas was 1.11 U/g.
¹²⁵1-porcine-insulin bound with the patient's serum was separated each other by acidification. The insulin binding protein was classified as IgG, and the light chain was K type. On the other hand, a control study showed that the insulin antibodies of the insulin treated patients were IgG, IgA and IgM, and the light chain was K and L type. Protein fraction, obtained by acidified gel filtration from the serum, reacted well with human and porcine insulin, but less with bovine insulin. A passive cutaneous allergic reaction was positive in a guinea pig and negative in other guinea pig. Precipitation reaction by the method of Ochterlony was not demonstrated. After the operation the insulin binding capacity of her antibody decreased gradually, but it was still recognized six months after operation. It was concluded that the insulin binding protein in the serum might be auto-antibody to the endogenous insulin, because she had never recieved any insulin injection.