Insulin autoimmune syndrome: Experience at a tertiary care centre

ABSTRACT

Introduction: Insulin autoimmune syndrome (Hirata's disease) is a rare cause of hypoglycemia characterised by recurrent hypoglycemic episodes due to insulin autoantibodies, without any prior exposure to insulin. Method: Retrospective review of patients with hyperinsulinemichypoglycemiawas done. 10 patients (8 females), aged between 7 to 60 years (mean 42.9 years), from year 2005 to 2021 were assessed. Results: Four patients presented with fasting hypoglycemia, while all of them had post-absorptive hypoglycemic episodes. Four (40%) patients had evidence of other autoimmune conditions (three Hashimoto's thyroiditis & one autoimmune cholangiopathy). Mean insulin was 2782uIU/mL (61-14,332), and mean C-peptide was 12.9 ng/dL (3.6-37.6). Mean anti insulin antibody level was 77.8% (13.6-98.82) in samples evaluated by RIA (till 2015), and 84.7 u/mL by ELISA (2016 onwards). Three (30%) patients had positive history of offending drug usage (clopidpgrel, torsemide and pantoprazole). One of the patients had history of Covid-19 infection three months prior. Treatment with low carbohydrate diet, alpha glucosidase inhibitor & /or prednisolone was effective in all symptomatically. Conclusion: In hyperinsulinemichypoglycemia, when insulin is markedly elevated, but C-peptide is only moderately elevated, insulin autoimmune syndrome should be suspected and insulin in dilution and anti-insulin antibody should be checked. Also, history of other autoimmune conditions, and history of any offending drug usage should be diligently investigated in these patients.