CSEMO1 - Unmasking Autoimmune Insulin Syndrome: A Rare Cause of Recurrent Hypoglycemia

Abstract:

Introduction: Insulin Autoimmune Syndrome (IAS), or Autoimmune hypoglycemia, is a rare autoimmune condition, characterized by antibodies against insulin and spontaneous hypoglycemia. The diagnosis can be challenging leading to poor clinical outcomes.

Clinical

Case: A 37-year-old, previously healthy woman, presented with acute onset episodes of symptomatic hypoglycemia (venous glucose: 2.3 mmol/L). No prior history of systemic disorders including autoimmune conditions and was not receiving any medications. Baseline blood testing showed hyperinsulinemic (insulin >2000 pmol/L) hypoglycemia (glucose 2.6 mmol/), normal liver function tests and HbA1c of 5.6%. Magnetic resonance and nuclear somatostatin receptor imaging were unremarkable. Insulin auto-antibodies (IAA), however, were highly reactive.
A 75 gr oral glucose tolerance test (OGTT) elicited a hyperinsulinemic (insulin >4304 pmol/L) hypoglycemic (glucose 1.2 mmol/L) response at the 4hr (Figure 1). Positive IAA were detected with insulin recovery post PEG precipitation of < 5%, supporting the diagnosis of IAS. Treatment with prednisone 10 mg/day with restriction of simple carbohydrate diet resulted in clinical improvement within 2 weeks as well as decreases in immunoreactive insulin levels and IAA titers (Table 1). As the IAA remained positive, an OGTT was completed 20 months later (Figure 1).

Discussion: IAS should be suspected in patients presenting with hypoglycemia and inappropriate insulin secretion, increased insulin/c-peptide molar ratio >1, particularly with a history of autoimmune disorders, and/or with sulfa drug ingestion. First line treatment is stopping the putative IAS-related medication and maintaining a diet that avoids simple carbohydrates. For those with refractory severe hypoglycemia, alfa glucosidase inhibitors and glucocorticoids can be effective.