Abstract
Two types of antibody could confuse the differential diagnosis of hypoglycaemia. One is insulin-binding autoantibodies (IAA), a double hit causing hypoglycaemia of insulin autoimmune syndrome (IAS, also known as Hirata's disease) as well as distorting measurements of insulin and/or C-peptide. The clinical manifestations and initial endocrine results in patients with IAS would mimic and masquerade as other common pathologies, as well as factitious hypoglycaemia in adults, children and newborns. The second type is non-IAA autoantibodies which, if fortuitously/incidentally present in patients with hypoglycaemia, could interfere with insulin and/or C-peptide immunoassay measurements, also confusing differential diagnosis. Currently, testing for antibodies (all classes/subclasses) by simple method such as polyethylene glycol (PEG) is not usually included among first-line investigations of hypoglycaemia, causing delayed diagnosis or diagnostic misapplication. Detection of antibodies, irrespective of their nature, warrants cautious and careful differential diagnosis, averting hospitalisation and curtailing unnecessary and expensive investigations.