Hypoglycaemia due to insulin autoimmune syndrome: report of two cases with characterisation of HLA alleles and insulin autoantibodies

Exogenous insulin autoimmune syndrome: A case report and review of literature

BACKGROUND

Insulin autoimmune syndrome (IAS) is a severe manifestation of spontaneous hypoglycemia. It is characterized by elevated levels of immune-reactive insulin and highly potent insulin autoantibodies (IAAs), which are induced by endogenous insulin circulating in the bloodstream. It is distinguished by recurring instances of spontaneous hypoglycemia, the presence of IAA within the body, a substantial elevation in serum insulin levels, and an absence of prior exogenous insulin administration. Nevertheless, recent studies show that both conventional insulin and its analogs can induce IAS episodes, giving rise to the notion of non-classical IAS. Therefore, more attention should be paid to these diseases.

CASE SUMMARY

In this case report, we present a rare case of non-classical IAS in an 83-year-old male patient who present with symptoms of a psychiatric disorder. Upon symptom onset, the patient exhibited Whipple's triad (including hypoglycemia, blood glucose level less than 2.8 mmol/L during onset, and rapid relief of hypoglycemic symptoms after glucose administration). Concurrently, his serum insulin level was significantly elevated, which contradicted his C-peptide levels. After a comprehensive examination, the patient was diagnosed with exogenous insulin autoimmune syndrome. Considering that the patient had type 2 diabetes mellitus and a history of exogenous insulin use before disease onset, it was presumed that non classical IAS was induced by this condition. The PubMed database was used to search for previous cases of IAS and non-classical IAS to analyze their characteristics and treatment approaches.

CONCLUSION

The occurrence of non-classical IAS is associated with exogenous insulin or its analogs, as well as with sulfhydryl drugs. Symptoms can be effectively alleviated through the discontinuation of relevant medications, administration of hormones or immunosuppressants, plasma exchange, and lifestyle adjustments.

Resolution of dysglycaemia after treatment of monoclonal gammopathy of endocrine significance

In very rare cases of monoclonal gammopathy, insulin-binding paraprotein can cause disabling hypoglycaemia. We report a 67-year-old man re-evaluated for hyperinsulinaemic hypoglycaemia that persisted despite distal pancreatectomy. He had no medical history of diabetes mellitus or autoimmune disease but was being monitored for an IgG kappa monoclonal gammopathy of undetermined significance. On glucose tolerance testing, hyperglycaemia occurred at 60 min (glucose 216 mg/dL) and hypoglycaemia at 300 min (52 mg/dL) concurrent with an apparent plasma insulin concentration of 52 850 pmol/L on immunoassay. Laboratory investigation revealed an IgG2 kappa with very high binding capacity but low affinity (Kd 1.43 × 10-6 mol/L) for insulin. The monoclonal gammopathy was restaged as smouldering myeloma not warranting plasma cell-directed therapy from a haematological standpoint. Plasma exchange reduced paraprotein levels and improved fasting capillary glucose concentrations. Lenalidomide was used to treat disabling hypoglycaemia, successfully depleting paraprotein and leading to resolution of symptoms.

Increased C-Peptide Immunoreactivity in Insulin Autoimmune Syndrome (Hirata Disease) Due to High Molecular Weight Proinsulin

Background

Determination of C-peptide is important in the investigation of unexplained hyperinsulinemic hypoglycemia because a high C-peptide concentration usually indicates endogenous insulin hypersecretion. Insulin autoimmune syndrome (IAS) denotes hyperinsulinemic hypoglycemia due to insulin-binding antibodies that prolong insulin half-life. C-peptide clearance is considered to be unaffected, and although a marked C-peptide immunoreactivity in hypoglycemic samples has been reported, it has been suspected to be artifactual. High-resolution mass spectrometry enables examination of the basis of C-peptide-immunoreactivity in IAS.

Methods

Precipitation of plasma with polyethylene glycol was followed by C-peptide immunoassay. Plasma peptides extracted by solvent precipitation were characterized by nano-LC–MS/MS and analyzed using an untargeted data-dependent method. Peptides related to proinsulin, in amino acid sequence, were identified using proprietary bioinformatics software and confirmed by repeat LC–MS/MS analysis. Gel filtration chromatography coupled to LC–MS/MS was used to identify proinsulin-related peptides present in IAS immunocomplexes. Results were compared with those from C-peptide immunoassay.

Results

Polyethylene glycol precipitation of IAS plasma, but not control plasma, depleted C-peptide immunoreactivity consistent with immunoglobulin-bound C-peptide immunoreactivity. LC–MS/MS detected proinsulin and des 31,32 proinsulin at higher abundance in IAS plasma compared with control plasma. Analysis by gel filtration chromatography coupled to LC–MS/MS demonstrated proinsulin and des 31,32 proinsulin, but no C-peptide, in plasma immunocomplexes.

Conclusions

Antibody binding can enrich proinsulin and des 31,32 proinsulin in IAS immunocomplexes. Proinsulin cross-reactivity in some C-peptide immunoassays can lead to artifactually increased C-peptide results.

Insulin autoimmune syndrome: a rare cause of spontaneous hypoglycaemia in non-diabetic individuals

Insulin autoimmune syndrome (IAS) is a rare cause of hypoglycaemia, characterised by recurrent hypoglycaemic episodes secondary to insulin autoantibodies in individuals who are not exposed to exogenous insulin. We are reporting a case of IAS in a 64-year-old gentleman, who presented with predominant postprandial hypoglycaemic episodes. On biochemical evaluation, he was found to have hyperinsulinemic hypoglycaemia. Localisation studies with MRI abdomen and endoscopic ultrasound (EUS) were negative for pancreatic tumour. Tests sent for insulin antibody levels were elevated. The patient was treated with frequent meals, acarbose and glucocorticoids. Patient condition improved and did not experience hypoglycaemia on follow-up.

Insulin Autoimmune Syndrome (Hirata Disease): A Comprehensive Review Fifty Years After Its First Description

Insulin autoimmune syndrome (IAS), also named Hirata's disease, is a rare condition characterized by hypoglycemic episodes due to the presence of high titers of insulin autoantibodies (IAA). IAS is a form of immune-mediated hypoglycemia, which develops when a triggering factor (ie, a medication or a viral infection) acts on an underlying predisposing genetic background. IAS pathogenesis involves the formation of insulin-IAA complexes that induce glycemic alterations with a double-phase mechanism: IAA prevent insulin to bind its receptor in the postprandial phase, possibly resulting in mild hyperglycemia; thereafter, insulin is released from the complexes irrespective of blood glucose concentrations, thus inducing hypoglycemia. The diagnosis of IAS is challenging, requiring a careful workup aimed at excluding other causes of hyperinsulinemic hypoglycemia. The gold standard for the definitive diagnosis is the finding of IAA in a blood sample. Because IAS is frequently a self-remitting disease, its management mostly consists of supportive measures, such as dietary modifications, aimed at preventing the development of hypoglycemia. Pharmacological therapies may occasionally be necessary for patients presenting with severe manifestations of IAS. Available therapies may include drugs that reduce pancreatic insulin secretion (somatostatin analogues and diazoxide, for instance) and immunosuppressive agents (glucocorticoids, azathioprine and rituximab). The purpose of this review is to provide a comprehensive analysis of the disease, by describing the burden of knowledge that has been obtained in the 50 years following its first description, took in 1970, and by highlighting the points that are still unclear in its pathogenesis and management.

Development of autoantibodies precedes clinical manifestations of autoimmune diseases: A comprehensive review

The etiology of autoimmune diseases is due to a combination of genetic predisposition and environmental factors that alter the expression of immune regulatory genes through various mechanisms including epigenetics. Both humoral and cellular elements of the adaptive immune system play a role in the pathogenesis of autoimmune diseases and the presence of autoantibodies have been detected in most but not all autoimmune diseases before the appearance of clinical symptoms. In some cases, the presence or levels of these autoantibodies portends not only the risk of developing a corresponding autoimmune disease, but occasionally the severity as well. This observation is intriguing because it suggests that we can, to some degree, predict who may or may not develop autoimmune diseases. However, the role of autoantibodies in the pathogenesis of autoimmune diseases, whether they actually affect disease progression or are merely an epiphenomenon is still not completely clear in many autoimmune diseases. Because of these gaps in our knowledge, the ability to accurately predict a future autoimmune disease can only be considered a relative risk factor. Importantly, it raises the critical question of defining other events that may drive a patient from a preclinical to a clinical phase of disease.

Hyperinsulinemic hypoglycemia associated with insulin antibodies caused by exogenous insulin analog

Insulin antibodies (IA) associated with exogenous insulin administration seldom caused hypoglycemia and had different characteristics from insulin autoantibodies (IAA) found in insulin autoimmune syndrome (IAS), which was first described by Dr Hirata in 1970. The characteristic of IAS is the presence of insulin-binding autoantibodies and related fasting or late postprandial hypoglycemia. Here, we report a patient with type 1 diabetes mellitus under insulin glargine and insulin aspart treatment who developed recurrent spontaneous post-absorptive hyperinsulinemic hypoglycemia with the cause probably being insulin antibodies induced by exogenous injected insulin. Examinations of serial sera disclosed a high titre of insulin antibodies (33%, normal <5%), high insulin concentration (111.9 IU/mL) and undetectable C-peptide when hypoglycemia occurred. An oral glucose tolerance test revealed persistent high serum levels of total insulin and undetectable C-peptide. Image studies of the pancreas were unremarkable, which excluded the diagnosis of insulinoma. The patient does not take any of the medications containing sulfhydryl compounds, which had been reported to cause IAS. After administering oral prednisolone for 3 weeks, hypoglycemic episodes markedly improved, and he was discharged smoothly.

LEARNING POINTS

Insulin autoimmune syndrome (IAS) or IAS-like situation should be one of the differential diagnosis in patients with hyperinsulinemic hypoglycemia.Although less reported, insulin antibodies (IA) caused by exogenous insulin analog should be considered as the cause of hypoglycemia.Patients with suspected insulin autoimmune syndrome (IAS) should be screened for drugs related to autoimmunity to endogenous insulin.

Insulin Autoimmune Syndrome Accompanied by Multiple Myeloma

In 1981, a 48-year old man was diagnosed with insulin autoimmune syndrome. In 2005, he experienced a substantial increase in his monoclonal insulin antibody levels; in 2006 and 2007, serum monoclonal gammopathy and an 11% marrow plasmacyte ratio were confirmed. In 2012, asymptomatic multiple myeloma was diagnosed based on an increased γ-globulin fraction and serum M-protein (IgG) levels. The insulin antibody binding rate was 75.4% in 2005 and 78.8% in 2012. In 2012, he was hospitalized for ileus and died. Autopsy identified multiple myeloma and no endocrinological tumors in the pancreas.

Two Sisters with Graves' Disease and Similar Clinical Features who Tested Positive for Anti-insulin Antibodies after Thiamazole Treatment

The older of a pair of sisters experienced hypoglycemia after the start of thiamazole (MMI) treatment. Based on a high insulin antibody level, she was diagnosed with insulin autoimmune syndrome (IAS). HLA-DNA typing identified DRB1*04:06. Although a 75-g oral glucose tolerance test (OGTT) showed biphasic insulin secretion, the secretion pattern became monophasic after discontinuation of the MMI. The younger sister was diagnosed with IAS after the start of MMI treatment. HLA-DNA typing identified DRB1*04:06. The 75-g OGTT showed biphasic insulin secretion, but it became monophasic after discontinuation of the MMI. According to the similar insulin secretion kinetics in the two sisters with IAS, we suspect that a genetic predisposition may be associated with the features of anti-insulin antibodies.

Unusual Manifestations of Essential Monoclonal Gammopathy. II. Simulation of the Insulin Autoimmune Syndrome

In rare cases, the monoclonal immunoglobulin that characterizes essential monoclonal gammopathy interacts with a self-antigen with functional consequences and a resulting clinical syndrome. This event is presumably random and results from the clone of B lymphocytes making a monoclonal immunoglobulin that simulates an autoimmune antibody. Thus, by chance, the monoclonal immunoglobulin has sufficient affinity for an epitope on a normal protein that functional consequences ensue. One such rare event is the synthesis and secretion of a monoclonal immunoglobulin that binds to human insulin. Inactivation of insulin by antibody results in (1) an early postprandial hyperglycemia, (2) followed by either or both (i) a reactive overshot in insulin secretion, as a result of hypertrophied or hyperplastic islet beta cells, later falling glucose levels, and (ii) an unpredictable dissociation of insulin from the complex, and, several hours later, (3) a resultant increase in free insulin levels and severe hypoglycemia with clinical consequences, ranging from sweating, dizziness, headache, and tremors to confusion, seizures, and unconsciousness. These attacks are invariably responsive to glucose administration. This very uncommon manifestation of a monoclonal gammopathy can occur in patients with essential monoclonal gammopathy or myeloma. The monoclonal anti-insulin immunoglobulin in monoclonal gammopathy has a low affinity for insulin, but has a high capacity for insulin-binding, resulting in the syndrome of episodic hypoglycemic attacks. This phenomenon of an insulin-binding monoclonal immunoglobulin simulates the acquired insulin autoimmune syndrome, although the latter is mediated by a polyclonal antibody response in the majority of cases studied, and has linkage to HLA class II alleles.

Hypoglycemic coma due to insulin autoimmune syndrome induced by methimazole: A rare case report

Insulin autoimmune syndrome (IAS) is a rare cause of hypoglycemia characterized by the presence of insulin-binding autoantibodies and fasting or late postprandial hypoglycemia. The number of reports on the association of human leukocyte antigen (HLA) genotype with this disease in adolescents in China is limited. This is the case report of a 17-year-old female patient with Graves' disease who was treated with methimazole (MTZ). After 4 weeks of continuous MTZ treatment, the patient suffered an episode of unconsciousness during the late postprandial phase and was admitted to the hospital, where the blood glucose level was found to be 2.88 mmol/l. The symptoms were relieved following intravenous glucose administration. Imaging studies of the pancreas were unremarkable, but the laboratory investigations on admission revealed high serum levels of total insulin, associated with relatively low levels of free insulin and markedly elevated insulin autoantibody (IAB) levels. HLA testing revealed DRB1*0406/0901 and the patient discontinued MTZ and was prescribed propylthiouracil. During the long-term follow-up, the total insulin and IAB levels gradually declined. There was no other episode of hypoglycemia. Therefore, in adolescents with Graves' disease receiving antithyroid treatment with MTZ who experience hypoglycemia, the IAB levels should be assessed to exclude or confirm IAS as the underlying cause.

[Endogenous hyperinsulinism: two diagnostic challenges]

Hypoglycemia in apparently healthy adults is a rare finding in clinical practice requiring a thorough investigation of the cause. During the investigation, identification of hypoglycemia associated with inappropriately high levels of insulin and C-peptide should prompt the exclusion of rare causes of hypoglycemia, including pancreatic islet-cells disease and autoimmune hypoglycemia. In this paper, we describe two cases of hypoglycemia associated with endogenous hyperinsulinism, whose causes are uncommon in clinical practice, and review important aspects of the diagnosis and treatment of hyperinsulinemic hypoglycemia.

Analytical and clinical challenges in a patient with concurrent type 1 diabetes, subcutaneous insulin resistance and insulin autoimmune syndrome

A lean 15-year-old girl was diagnosed with type 1 diabetes based on symptomatic hyperglycaemia and positive anti-islet cell antibodies. Glycaemia was initially stabilised on twice-daily mixed insulin. After 11 months from the time of diagnosis, she complained of hyperglycaemia and ketosis alternating with hypoglycaemia. This progressively worsened until prolonged hospital admission was required for treatment of refractory hypoglycaemia. A high titre of anti-insulin antibodies was detected associated with a very low recovery of immunoreactive (free) insulin from plasma after precipitation with polyethylene glycol, suggesting the presence of insulin in bound complexes. Insulin autoimmune syndrome was diagnosed and metabolic fluctuations were initially managed supportively. However, due to poor glucose control, immunosuppressive therapy was initiated first with steroids and plasmapheresis and later with anti-CD20 antibody therapy (Rituximab). This treatment was associated with a gradual disappearance of anti-insulin antibodies and her underlying type 1 diabetes has subsequently been successfully managed with an insulin pump.

LEARNING POINTS

Anti-insulin antibodies may result in low levels of free insulin.Polyclonal anti-insulin antibodies can interfere with the pharmacological action of administered insulin, resulting in hypoglycaemia and insulin resistance, due to varying affinities and capacities.In this patient, rituximab administration was associated with a gradual disappearance of anti-insulin antibodies.It is hypothesised that this patient had subcutaneous insulin resistance (SIR) caused by insulin capture at the tissue level, either by antibodies or by sequestration.A prolonged tissue resistance protocol may be more appropriate in patients with immune-mediated SIR syndrome.

Development of insulin antibodies and changes in titers over a long-term period in patients with type 2 diabetes

BACKGROUND

Recently, insulin analogs have become widely used for the treatment of diabetes. The aim of this study was to determine differences in the antigenicity of insulin analogs and long-term changes in titers in patients with type 2 diabetes.

METHODS

Insulin antibodies were examined using polyethylene glycol and protein G methods in 381 patients with type 2 diabetes.

RESULTS

Insulin antibodies were detected in 48 of 118 patients (40.7%) who used insulin, and insulin glargine and aspart were more antigenic. Insulin antibodies were unexpectedly found in seven of 263 patients (2.7%) who had never used insulin. Serum insulin concentrations in patients with insulin antibodies were significantly higher than those without them. Two years after the initial evaluation, insulin antibodies were still positive in 92.7% of patients who used insulin; while, they disappeared in all patients who had never used insulin. A patient who stopped insulin injections 6years ago was found to be positive for insulin antibodies at the first evaluation as well as 2years later.

CONCLUSIONS

Insulin glargine and aspart induced insulin antibodies more frequently, and insulin antibodies remained in patients for a long time. Insulin antibodies should be suspected even in patients not currently on insulin therapy.

Recurrent Drug-Induced Insulin Autoimmune Syndrome in a Patient with Premature Ovarian Failure

Insulin autoimmune syndrome (IAS) is characterized by hypoglycemic attacks, very high insulin levels and the presence of circulating autoantibodies to insulin in patients who have not been treated with exogenous insulin. Approximately half of patients with insulin autoimmune syndrome have a medication history preceding hypoglycemic events. We present the case of a young woman with premature ovarian failure who developed IAS initially after treatment with methimazole and several years later after captopril, and because of coexistent premature ovarian failure was classified as having autoimmune polyglandular syndrome (APS) type 3. Termination of methimazole and Captopril treatment resulted in the disappearance of hypoglycemic episodes. We discuss diagnostic and treatment dilemmas associated with discovering and management of IAS and APS in this patient.

Autoimmune forms of hypoglycemia

Autoimmune syndromes are a rare cause of hypoglycemia characterized by elevated levels of insulin in the presence of either anti-insulin antibodies (insulin autoimmune syndrome) or anti-insulin receptor antibodies (type B insulin resistance). Insulin autoimmune syndrome is the third leading cause of hypoglycemia in Japan, but has rarely been described in the non-Asian population.In the current study, we report the clinical and biochemical characteristics and clinical course of 2 white patients with insulin autoimmune syndrome, and present a literature review of non-Asian patients reported with insulin autoimmune syndrome. Also, we describe the clinical and biochemical characteristics of patients reported in the literature with type B insulin resistance who manifested hypoglycemia. We compare the clinical and laboratory features of insulin autoimmune syndrome and type B insulin resistance with each other and with other forms of hyperinsulinemic hypoglycemia.Autoimmune forms of hypoglycemia are uncommon. However, they should be considered in any patient with hypoglycemia in the setting of unsuppressed insulin levels associated with anti-insulin or anti-insulin receptor antibodies. Making the correct diagnosis may spare a hypoglycemic patient from an unnecessary pancreatic surgical procedure.

Hypoglycaemia and fits in a thyrotoxic man

We report prolonged severe hypoglycaemia with raised serum insulin levels in a Sri Lankan man with recently diagnosed Graves disease being treated with carbimazole. We diagnosed insulin autoimmune syndrome on the basis of raised anti-insulin antibody levels, and this diagnosis was supported by the subsequent course of the illness. The patient recovered completely after carbimazole was replaced with propylthiouracil and he was treated with dextrose infusions, frequent high-carbohydrate meals and a course of prednisolone.

Severe hypoglycaemia in a person with insulin autoimmune syndrome accompanied by insulin receptor anomaly type B

AIMS

A rare case of the insulin autoimmune syndrome (IAS) accompanied by insulin receptor anomaly is reported.

METHODS

Antibodies to insulin and insulin receptor were determined in the patient with severe hypoglycaemia before and after the treatment with prednisolone.

RESULTS

Titers of antibody to insulin and insulin receptors were 73.0% and 41.5%, respectively. Drug-induced lymphocyte stimulation tests were all negative for the suspicious drugs. Her HLA-DR was DRB1*0403/04051. Following steroid therapy, the formation of antibodies was suppressed and alleviated her symptoms. Scatchard analysis yielded findings specific to polyclonal antibodies.

CONCLUSIONS

The changes in autoantibodies resulted in alleviation of the hypoglycemic symptoms as a result of steroid therapy.

Hypoglycemia due to an insulin binding antibody in a patient with an IgA-kappa myeloma

CONTEXT

Autoantibodies to insulin have been described to cause spontaneous hypoglycemia in nondiabetic subjects. There have been occasional reports of spontaneous hypoglycemia due to monoclonal anti-insulin antibodies. We present the first report of a patient with an IgA-kappa myeloma in whom frequent hypoglycemia resulted from the ability of the monoclonal IgA-kappa to bind insulin.

OBJECTIVES

The aim of this study was to describe the occurrence of profound hypoglycemia in a patient with IgA-kappa myeloma, characterize biochemically the nature of the IgA:insulin complex present, and place this case in the context of the published literature on hypoglycemia resulting from autoantibodies to insulin.

DESIGN

A case study was performed.

PATIENTS

A single case of profound hypoglycemia associated with IgA-kappa myeloma was studied.

INTERVENTION

There were no interventions.

MAIN OUTCOME MEASURES

A case study was performed.

RESULTS

Polyethylene glycol precipitation and gel filtration chromatography were used to demonstrate high-molecular weight insulin immunoreactivity in the patient's plasma. This was characterized as an insulin binding IgA-kappa paraprotein present at 4200 mg/dl (42 g/liter) with a relatively high insulin dissociation constant of 0.32 microm/liter using radiolabelled insulin binding studies.

CONCLUSIONS

We present the first case of hypoglycemia due to IgA binding insulin antibodies in a patient with an IgA-kappa paraprotein myeloma. The hypoglycemia was associated with high-plasma insulin levels and relatively low C-peptide levels. A plausible mechanism for the hypoglycemia is the delayed clearance of insulin. This case broadens the spectrum of monoclonal gammopathies that have been associated with anti-insulin reactivity and spontaneous hypoglycemia.

Lipid contribution to the affinity of antigen association with specific antibodies conjugated to liposomes

Immunoliposomes, directed to clinically relevant cell-surface molecules with antibodies, antibody fragments or peptides, are used for site-specific diagnostic evaluation or delivery of therapeutic agents. We have developed intrinsically echogenic liposomes (ELIP) covalently linked to fibrin(ogen)-specific antibodies and Fab fragments for ultrasonic imaging of atherosclerotic plaques. In order to determine the effect of liposomal conjugation on the molecular dynamics of fibrinogen binding, we studied the thermodynamic characteristics of unconjugated and ELIP-conjugated antibody molecules. Utilizing radioimmunoassay and enzyme-linked immunosorbent assay protocols, binding affinities were derived from data obtained at three temperatures. The thermodynamic functions DeltaH(o) , DeltaG(o) and DeltaS(o) were determined from van't Hoff plots and equations of state. The resultant functions indicated that both specific and nonspecific associations of antibody molecules with fibrinogen occurred through a variety of molecular interactions, including hydrophophic, ionic and hydrogen bonding mechanisms. ELIP conjugation of antibodies and Fab fragments introduced a characteristic change in both DeltaH(o) and DeltaS(o) of association, which corresponded to a variable contribution to binding by phospholipid gel-liquid crystal phase transitions. These observations suggest that a reciprocal energy transduction, affecting the strength of antibody-antigen binding, may be a singular characteristic of immunoliposomes, having utility for optimization and further development of the technology.

Insulin Autoimmune Syndrome possibly caused by alpha lipoic acid

Insulin Autoimmune Syndrome (IAS) is a rare disease characterized by hypoglycemia and autoantibodies to insulin without prior insulin administration. Here, we report a case of IAS associated with alpha lipoic acid (ALA). The patient is a 55-year-old man. He began to complain of hypoglycemic symptoms after taking ALA. He lost consciousness in the late postprandial period and blood glucose was found to be 27 mg/dl. A high insulin level and high titers of insulin antibodies were detected. His HLA genotype contains DRB1* 0406. As ALA comes to be used widely, the incidence of IAS due to ALA might increase.

Insulin Autoimmunity and Hypoglycemia in Seven White Patients

OBJECTIVE

To report the clinical, biochemical, and immunologic characteristics of 7 white patients with the rare disorder of hyperinsulinemic hypoglycemia in association with spontaneously generated high titers of antibodies to human insulin.

METHODS

We reviewed the clinical data, history, and symptoms of the 7 study patients and summarized the biochemical findings during a spontaneous episode of hypoglycemia. Insulin antibody binding was measured in all patients, and antibody affinity, capacity, and clonality were analyzed in 4. A mixed meal study was conducted in 2 patients. A potential mechanism for postprandial hypoglycemia is presented.

RESULTS

In all 7 patients (6 women and 1 man), symptoms were neuroglycopenic, occurring primarily postprandially but during fasting in some patients. During hypoglycemia, concentrations of insulin, proinsulin, and, in most patients, C peptide considerably exceeded those observed in patients with insulinoma. These concentrations were spuriously elevated as a result of interference by the autoantibodies in the immunoassays. No patient had evidence of an insulinoma on various radiologic localization procedures directed at the pancreas. Insulin antibodies showed a high percentage of binding to human insulin--50 to 90%. Heterogeneity of antibodies regarding clonality and antibody binding sites was noted; some patients had polyclonal and some had monoclonal IgG class antibodies. Most patients had two categories of binding sites: high affinity/low capacity and low capacity/high affinity. Although the mechanism for postprandial hypoglycemia remains conjectural, prolonged elevations of postprandial concentrations of total and free insulin are consistent with the putative mechanism of a buffering effect of insulin antibodies.

CONCLUSION

Insulin autoimmune hypoglycemia, although rare in any racial group and especially in white subjects, can be readily detected by high titers of insulin antibodies. Such a determination should be done in all patients undergoing evaluation for hypoglycemia.

Insulin autoimmune syndrome: case report

CONTEXT

Insulin autoimmune syndrome (IAS, Hirata disease) is a rare cause of hypoglycemia in Western countries. It is characterized by hypoglycemic episodes, elevated insulin levels, and positive insulin antibodies. Our objective is to report a case of IAS identified in South America.

CASE REPORT

A 56-year-old Caucasian male patient started presenting neuroglycopenic symptoms during hospitalization due to severe trauma. Biochemical evaluation confirmed hypoglycemia and abnormally high levels of insulin. Conventional imaging examinations were negative for pancreatic tumor. Insulin antibodies were above the normal range. Clinical remission of the episodes was not achieved with verapamil and steroids. Thus, a subtotal pancreatectomy was performed due to the lack of response to conservative treatment and because immunosuppressants were contraindicated due to bacteremia. Histopathological examination revealed diffuse hypertrophy of beta cells. The patient continues to have high insulin levels but is almost free of hypoglycemic episodes.