Background/Aim: Insulin autoimmune syndrome (IAS) is a rare disorder characterised by hypoglycaemia due to insulin autoantibodies. Prior exposure to certain viruses has been implicated in the pathogenesis. There is little literature on the relationship between IAS and SARS-CoV-2.
Method: We reviewed a case of symptomatic hyperinsulinaemic hypoglycaemia associated with markedly elevated insulin antibody and prior COVID-19 infection. We performed a literature review on IAS and potential mechanisms of SARS-CoV-2 in the pathogenesis.
Result: A 51-year-old non-diabetic patient was admitted with hypoglycaemia. Multiple stereotypical episodes of sweating and hot flushes had been occurring in the prior week. She had COVID-19 infection 4 weeks prior. 72-hour fasting test confirmed hyperinsulinaemic hypoglycaemia. At termination, she was symptomatic with glucose level 2.6mmol/L, insulin level 169mU/L, and c-peptide level 1.1nmol/L. Sulphonylurea screen was negative. MRI, contrast CT, Dotatate PET/CT and endoscopic US did not identify a source of hyperinsulinaemia. However, her insulin antibody was markedly elevated at 4243U/ml (Normal≤0.4U/ml). She was treated with high-dose Prednisolone. Her insulin antibody significantly decreased with no further hypoglycaemia.
A growing number of autoimmune diseases following COVID-19 infection have been observed(1). We found two similar reports of hypoglycaemia, one of which was confirmed IAS(2,3). It is proposed that post-COVID-19 autoimmunity is due to immune reconstitution following transient immune suppression(4). This is a well-known phenomenon in other viral infections e.g. coxsackie B and hepatitis C, both of which have been implicated in IAS(5-7). Additionally, the pancreatic islet is a target tissue of SARS-CoV-2 driven by ACE2 expression(8). Recent studies have suggested viral infections as triggers of pancreatic beta-cell autoimmunity through the production of cross-reactive antibodies due to molecular mimicry(9-12).
Conclusion: We highlighted a possible novel role of COVID-19 in the pathogenesis of IAS. Clinicians should consider COVID-19 as a potential cause when evaluating similar cases of non-diabetic hypoglycaemia.