Rare association of insulin autoimmune syndrome with ankylosing spondylitis

Insulin: Know what your immunoassay detects. Evaluation of two new immunoassays

BACKGROUND

Insulin is essential for glycemic regulation but diseases can cause a default or an excess of insulin secretion leading to dysregulated glycemia. Hence, measurement of insulinemia is useful to investigate hypoglycemia, determine the pathogenesis of diabetes and evaluate β-cell function. Thus, diabetic patients need supplementation with recombinant human insulin and/or insulin analogues. Analogues have primary sequences different from native human insulin and may not be detected by some immunoassays. The objective of our study was to evaluate new insulin immunoassays by determining their ability to detect different types of human insulin or analogues.

METHODS

This study compared the reactivity of two new insulin immunoassays with five well-established immunoassays on ten commercial insulins. We also measured insulin in blood samples from diabetic or pancreas transplant patients with known treatment.

RESULTS

Contrary to recombinant human insulin, there were differences in the specificity to insulin analogues. We distinguished three immunoassay categories: those recognizing all types of insulin such as the non-specific BI-INS-IRMA®, Architect® and Access® immunoassays; those recognizing human insulin only (Cobas®); and those recognizing human insulin and analogues in variable proportions (Liaison XL®, iFlash® and Maglumi®).

CONCLUSION

An accurate biological interpretation of insulinemia relies on knowledge of the specificity of the immunoassay used.

Insulin Autoimmune Syndrome - A Case Series

Insulin autoimmune syndrome, or Hirata's disease, is a rare cause of hypoglycaemia. It is characterised by spontaneous episodes of hypoglycaemia, without any exposure to exogenous insulin. The majority of cases are seen in the Japanese population and it is rarely found to affect other ethnicities. The recognition of this disease is important to avoid unnecessary investigations and procedures. Here, we report two cases of insulin autoimmune syndrome, which were diagnosed and managed in our institute.

Insulin Autoantibody Syndrome: Varying Clinical Presentations and Response Patterns of an Underrecognized Entity

CONTEXT

Insulin autoantibody syndrome (IAAS) is considered to be a rare cause of hyperinsulinaemic hypoglycaemia. Lack of familiarity with the varied clinical manifestations leads to underdiagnosis. Localization techniques aimed at insulin-secreting neoplasms and nesidioblastosis, which are expensive often are ordered when the correct diagnosis is not made.

AIMS

We describe the myriad of clinical manifestations associated with IAAS based on single centre experience.

SETTINGS AND DESIGN

Retrospective analysis of patients who got admitted with symptoms suggestive of hypoglycaemia and underwent mixed meal test and prolonged hypoglycaemic test from 2016 to 2019.

SUBJECTS AND METHODS

Retrospective data of 12 patients with IAAS who were diagnosed in the threeyear time period between 2016 and 2019 are included in this analysis. Clinical details, biochemical parameters and imaging modalities were analysed.

STATISTICAL ANALYSIS

All analyses were performed with SPSS software (version 17).

RESULTS

Total of twelve patients 12 (5 male and 7 females) were identified as IAAS. Median age of presentation was 57 years. Median insulin levels and median C-peptide levels were 300 miu/ml and 18.5 ng/ml respectively. Only 3 (25%) patients had spontaneous resolution. Steroid induced remission occurred by 3 months in the remaining patients. Intermittent hyperglycaemia was seen in 9 (75%) patients. Implicatable drug use preceding the occurrence of the clinical symptoms was observed in five patients.

CONCLUSION

IAAS is not uncommon in India. The diagnosis should be pursued in patients with hyperinsulinaemic hypoglycaemia especially when insulin levels are very high or when there is intermittent hyperglycaemia.

Rare Cause of Recurrent Hypoglycemia: Insulin Autoimmune Syndrome

We report a case of insulin autoimmune syndrome associated with several autoantibodies, presenting with recurrent hypoglycemia, predominantly in the postprandial period, which improved by dietary management and spontaneously resolved within two months. Differentiation from other causes of hyperinsulinemic hypoglycemia, such as insulinoma, is important to avoid unnecessary invasive procedures or surgical interventions. The 75-gram oral glucose tolerance test (OGTT) and mixed meal test showed a typical pattern, which may be useful indirect evidence of insulin autoimmune syndrome.