Pitfalls in the diagnosis of insulin autoimmune syndrome (Hirata's disease) in a hypoglycemic child: a case report and review of the literature.

Background Insulin autoimmune syndrome (IAS) is a rare cause of hyperinsulinemic hypoglycemia (HH) not addressed as a potential differential diagnosis in current pediatric guidelines. We present a case of IAS in a child with no previous history of autoimmune disease, no previous intake of triggering medications and absence of genetic predisposition. Case presentation A 6-year-old boy presented with recurrent HH (blood glucose of 26 mg/dL [1.4 mmol/L] and insulin of 686 µU/mL). Abdominal imaging was normal. After multiple therapeutic failures, we hypothesized misuse of exogenous insulin and factitious hypoglycemia. Council of Guardianship had the child separated from his mother, but insulin levels remained high. A chromatography test was then performed which showed high titers of endogenous insulin autoantibody (IAA) with early dissociation from the insulin molecule. The human leukocyte antigen (HLA) test showed a DRB1 *13:01/*08:02 genotype. The patient was advised to control food intake and physical activity routines. During a 5-year follow-up, hypoglycemic episodes were sparse, despite high insulin levels. Conclusions Misdiagnosis of IAS with factitious hypoglycemia may happen if IAS is not considered as a differential diagnosis, leading to potential traumatic consequences. Further efforts should be made to increase awareness of IAS as a differential diagnosis of hypoglycemia and to include it in pediatric guidelines.