A histopathologically diagnosed case of hypoglycemic encephalopathy due to insulin overdose

A 70-year-old man presented with cardiopulmonary arrest. Previous medical history included orally medicated diabetes mellitus, hypertension, stroke, and depression. The family observed that the patient had been sleeping for approximately 10 h. He was brought to the hospital and pronounced dead. Postmortem blood examinations revealed a blood insulin level of 0.54 μU/mL, C-peptide level of 0.14 ng/mL, and blood glucose of 9 mg/dL. Autopsy revealed an injection scar with intradermal hemorrhage and a subcutaneous hemorrhage in the left abdomen measuring 0.2 cm in diameter. Histopathological analysis revealed hemorrhage and inflammatory cell infiltration in the scar. Furthermore, subcutaneous adipose tissue, perivascular area, and neurons stained positive for anti-insulin antibody. HE staining of the brain revealed mild edema, and anti-GFAP antibody revealed clasmatodendrosis with bead-like staining of astrocyte subdivisions in the cerebral gray matter. Postmortem blood glucose evaluation is difficult because blood glucose levels are not stable and blood insulin is degraded relatively quickly. However, the cause of death was determined to be hypoglycemic encephalopathy due to insulin overdose because insulin was detected in the skin at the injection site. Furthermore, immunohistochemical examination of the brain revealed findings that were consistent with hypoglycemic encephalopathy. Therefore, histological examination was useful for postmortem diagnosis. J. Med. Invest. 71 : 340-342, August, 2024.