D1 MTE1 Case 1: Steroid refractory insulin autoimmune syndrome treated with rituximab and continuous glucose monitoring

A 67-year-old female presented with severe hypoglycaemia with a blood glucose of 34mg/dl 5 hours after having dinner. She did not have diabetes and had no access to oral hypoglycaemic agents, insulin, or any other drug known to cause hypoglycaemia. She was a known case of primary hypothyroidism euthyroid on treatment. The physical examination was unremarkable. Her liver, renal functions, thyroid, and adrenal functions were normal. At blood sugar of 23 mg/dl, her serum insulin was 24000uU/ml (normal<3uU/ml) and c-peptide was 16.2 ng/ml (normal 0-0.6ng/ml) which were very high. As the serum insulin levels were very high insulin autoimmune syndrome was suspected. Insulin autoantibodies were positive 87.2 units/ml (normal<12). Imaging with contrast-enhanced computerized tomography (CECT Abdomen), endoscopic ultrasonography, 68 gallium octreotide dotanoc whole-body PET -CT scan did not reveal any pancreatic or extra-pancreatic tumour. Autoimmune insulin syndrome (IAS) was diagnosed. She was started on high dose prednisolone, diazoxide and octreotide in addition to low carbohydrate meals. Hypoglycaemic episodes continued for 1 month despite this therapy. Remission was achieved only after 2 doses of Rituximab 1 gram infusion were given. Serum insulin levels were reduced to 230uU units from 24000uU/ml, and the patient's hypoglycaemic and hyperglycaemic episodes were normalized. We used continuous glucose monitoring using the Freestyle Libre glucose monitoring system, and the management of the patient was greatly facilitated with this.