Factitious Hypoglycemia in an Infant With Undetectable Exogenous Insulin by a Commercial Insulin Immunoassay: A Diagnostic Pitfall.

Factitious hypoglycemia in infancy is a rare, life-threatening manifestation of Munchausen syndrome by proxy (MSBP). The hallmark of such presentation is the detection of low c-peptide combined with high insulin at the time of hypoglycemia. We report the case of a male infant who presented with recurrent severe unexplained hypoglycemic episodes since the age of six months. Two of his siblings had similar unexplained hypoglycemia episodes at a young age. He was extensively investigated, and all were normal, for endocrine and metabolic etiologies. He underwent fundoplication and insertion of a gastrostomy tube with multiple lengthy hospital admissions. His mother had diabetes and was on insulin treatment; she also had mental health issues with family-related social stressors. His hypoglycemic attacks resolved once separated briefly from his mother on the ward, raising our suspicion of MSBP. The exogenous administration of insulin was only confirmed following a scheduled change of our local Insulin assay in our laboratory when his insulin was detectable with low C-peptide on one of his typical attacks. Apparently, our previous insulin immunoassay lacked sensitivity for his mother's long-acting insulin. We are reporting this case to raise awareness about this potential diagnostic pitfall.