Differential immunogenetic determinants of polyclonal insulin autoimmune syndrome (Hirata's disease) and monoclonal insulin autoimmune syndrome

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.

Recurrent hypoglycemia induced by clopidogrel: A case report and mini review

This report describes a patient who developed recurrent hypoglycemia episodes after 23 days of antiplatelet therapy with clopidogrel for left subclavian artery stent implantation. The patient suffered from palpitation, profuse sweating and weakness on the 23rd day of clopidogrel treatment. The minimum plasma glucose was 2.2 mmol/L, and the hypoglycemia was associated with significantly elevated levels of insulin. A diagnosis of insulin autoimmune syndrome (IAS) was made with the presence of insulin autoantibody and a comprehensive differential diagnosis of other conditions related with hypoglycemia. Clopidogrel was stopped, and the patient was treated with acarbose and had frequent low-carbohydrate meals; his hypoglycemia did not occur within 10 days. To date, seven cases of IAS induced by clopidogrel have been reported. Most reported cases were male aged in their 70s, and the hypoglycemic attack appeared 1-4 weeks after exposure to clopidogrel, characterized by severe hyperinsulinemia hypoglycemia with high titers of insulin autoantibodies. Most IAS cases can resolve spontaneously when they stop using the trigger medicine. Severe cases had been treated with drugs that reduce pancreatic insulin secretion (such as somatostatin and diazoxide), immunosuppressants (glucocorticoids, azathioprine and rituximab) and even immunoadsorption to remove the insulin autoantibody from the body. Considering the hypoglycemic attack might increase the risk of cardiovascular events among patients taking clopidogrel, we recommend that doctors should be aware of IAS as a rare severe adverse effect of clopidogrel, and be vigilant for the symptoms related with hypoglycemia in clopidogrel users.

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.

Clopidogrel as a Distinctive Cause of Insulin Autoimmune Syndrome: A Systematic Case Review

The sulfhydryl group of clopidogrel metabolite could induce insulin autoimmune syndrome (IAS) with hypoglycemia as the major symptom. For patients with cardiovascular disease taking clopidogrel for vascular protection, this adverse event hypoglycemia increases the risk of cardiovascular events. However, discontinuing clopidogrel leaves patients without appropriate antiplatelet therapy. Treating IAS with glucocorticoids is also risky for these patients' primary cardiovascular diseases. Early recognition and appropriate treatment of clopidogrel-induced IAS (CIAS) would be beneficial for patients. This research aimed to discover the clinical features and investigate optimal therapeutic management of CIAS. We systematically searched for cases of CIAS in PubMed and Embase and performed data mining in Food and Drug Administration Adverse Event Reporting System (FAERS). In the CIAS series, clinical features were summarized and compared to 287 IAS cases, including demographic information, HLA alleles, onset, and symptoms. The therapeutic effect of glucocorticoids was compared between the receiving group and the not-receiving group. The possibilities of common antiplatelet drugs to induce hypoglycemia/IAS were investigated with chemical structure and FAERS reports. A CIAS series of 51 patients was established. CIAS had an onset age of 74.8±8.6 years old, 92.2% male, and a balanced proportion of East Asians and non-East Asians. Confusion occurred more frequently in CIAS than in IAS from various causes, while the other symptoms and hypoglycemia types were similar. The recovery time was approximately the same whether using glucocorticoids/immunotherapy in CIAS or not. Among common antiplatelet drugs, ticagrelor and rivaroxaban were unlikely to induce hypoglycemia/IAS. Clopidogrel is a distinctive cause of IAS featuring an elderly male presenting confusion as the symptom of hypoglycemia. Glucocorticoids/immunotherapy might not be necessary for the long-term recovery of CIAS. To balance the risks of hypoglycemia and cardiovascular events, substituting clopidogrel with ticagrelor and rivaroxaban might be considered.

Hypoglycemia Caused by Exogenous Insulin Antibody Syndrome: A Large Single-Center Case Series From China

CONTEXT

Exogenous insulin antibody syndrome (EIAS) can lead to unexpected and potentially life-threatening recurrent hypoglycemia.

OBJECTIVE

We aimed to better define autoimmune hypoglycemia caused by EIAS in patients with diabetes and shed light on the improvements in the identification and intervention for this rare but possibly life-threatening condition.

METHODS

We summarized the clinical characteristics of autoimmune hypoglycemia caused by EIAS in 23 patients with diabetes. Furthermore, we performed human leukocyte antigen (HLA) genotyping of 10 patients.

RESULTS

We identified a high frequency of autoimmune comorbidities (21.7%), food or drug allergy (48%), insulin allergy (30%), lipodystrophy at the insulin injection sites (22%), and antinuclear antibodies (25%) in the patients. Alternation between hyperglycemia and hypoglycemia was observed in more than 90% of the patients. Most patients showed a high insulin autoantibody titer (>90%) and inappropriately increased insulin concentration (insulin/C-peptide molar ratio >7, >85%). We detected similar frequencies of DRB1*0405-DQB1*0401 and DRB1*0901-DQB1*0303 compared with previously reported frequencies in type 1 diabetes, and a lower frequency of DRB1*0406 compared with insulin autoimmune syndrome. The spontaneous remission rate exceeded 70%.

CONCLUSION

Predisposing factors for autoimmune hypoglycemia caused by EIAS include a strong autoimmune background. Susceptible HLA genotypes for type 1 diabetes or insulin autoimmune syndrome might not explain susceptibility to this condition. Additionally, insulin autoantibodies and the insulin/C-peptide molar ratio are reliable screening options. The prognosis for this condition is favorable. Monitoring of insulin and insulin autoantibodies may contribute to treatment effectiveness.

Hypoglycemia as a potential risk for patients taking clopidogrel: A systematic review and meta-analysis

BACKGROUND

Clopidogrel is a cornerstone antiplatelet drug used in cardiovascular, cerebrovascular, and peripheral artery diseases. The sulfhydryl group of clopidogrel metabolite could induce insulin autoimmune syndrome (IAS) with hypoglycemia as the major symptom. Discontinuing clopidogrel and substituting it with ticagrelor has been revealed as an effective treatment in previous studies. Since hypoglycemia serves as a risk factor for cardiovascular and cerebrovascular events, we aimed to determine the association between hypoglycemia/IAS and clopidogrel and to investigate whether clopidogrel is a modifiable and causal risk factor of hypoglycemia/IAS.

METHODS

MEDLINE, Embase, Cochrane databases, and clinical trial registries were searched for randomized controlled trials (RCTs) of clopidogrel from inception to 28 February 2022. RCTs comparing clopidogrel with placebo or other antiplatelet drugs were eligible if meeting the inclusion criteria: 1) clopidogrel was administrated 75 mg qd orally as a long-term antiplatelet prescription at least for months, and 2) hypoglycemia-inducible drugs were not used in the control arm. One investigator abstracted articles and performed a quality assessment. Uncertainties were resolved by discussions with two investigators independently. Odds ratio (OR) and risk difference (RD) were calculated and performed with subgroup analyses. The pre-specified protocol was registered in PROSPERO (CRD42022299622).

RESULTS

Six trials with 61,399 participants in total fulfilled the criteria and were included in the meta-analysis. Clopidogrel might not be associated with higher hypoglycemia odds (OR 0.95, 95% CI 0.65 to 1.40). However, Asian participants (p = 0.0437) seemed more likely to develop clopidogrel-associated hypoglycemia. Clopidogrel-associated hypoglycemia occurred at the highest rate of 0.03% (RD -0.00023, 95% CI -0.00077 to 0.00031), and this increased to 0.91% (RD 0.00210, 95% CI -0.00494 to 0.00914) in an aging population and to 0.18% (RD 0.00040, 95% CI -0.00096 to 0.00177) when Asian ratio of the population was elevated.

CONCLUSIONS

We raise the concern that clopidogrel might be a modifiable and causal risk factor of hypoglycemia. The Asian population might be more vulnerable and need additional care.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero, identifier CRD42022299622.

Case Report: Recurrent Autoimmune Hypoglycemia Induced by Non-Hypoglycemic Medications

We present a case of recurrent autoimmune hypoglycemia induced by non-hypoglycemic agents. We review reported cases of autoimmune hypoglycemia related to non-hypoglycemic agents, and discuss the effects of different detection methods for insulin autoantibodies on the results obtained. We aim to provide information for clinicians and a warning for medication usage. Considering the increasing number of clopidogrel-induced AIH cases and the hypoglycemia-induced increase in the risk of cardiovascular events, we recommend that cardiovascular disease patients being treated with clopidogrel be informed of this rare side effect and that clinicians be vigilant for the possibility of autoimmune hypoglycemia in this patient population.

Analysis of the clinical characteristics of insulin autoimmune syndrome induced by exogenous insulin in diabetic patients

BACKGROUND

The exact incidence, clinical features and uniform diagnostic criteria of exogenous insulin autoimmune syndrome (EIAS) are still unclear. The purpose of this study is to explore the clinical characteristics of EIAS and to provide a structural approach for clinical diagnosis, treatment and prevention.

METHODS

The literature on EIAS in Chinese and English from 1970 to 2020 was collected for retrospective analysis.

RESULTS

A total of 122 patients (33 males and 73 females) were included in the study with a median age of 67 years (range 14-86) and a median HbA1c of 7.7%. EIAS mainly occurred in type 2 diabetes mellitus patients using premixed insulin. Symptoms manifested were hypoglycemia in 86.54%, recurrent episodes of symptomatic hypoglycemia in 35.58%, nocturnal hypoglycemia along with daytime hyperglycemia in 21.15% and recurrent hypoglycemia after discontinued insulin in 64.43%. The onset of symptoms occurred at night, in the early morning or during fasting, ranging from a few days to 78 months after the administration of insulin. The mean blood glucose level during the hypoglycemic phase was 2.21 mmol/L (range 1-3.4), and the serum insulin levels were mainly ≥ 100 U/mL and were associated with low C-peptide levels (≤ 10 ng/ml). Insulin autoantibodies (IAAs) were positive in all EIAS patients. The 75-g extended oral glucose tolerance test (OGTT) mainly showed a diabetic curve. Pancreatic imaging was unremarkable. Withdrawal of insulin alone or combination of oral hypoglycemic agents or replacement of insulin formulations or with corticosteroid treatment eliminated hypoglycemia in a few days to 3 months. IAA turned negative in 6 months (median, range 1-12). No hypoglycemia episodes were observed at a median follow-up of 6 months (range 0.5-60).

CONCLUSIONS

EIAS is an autoimmune disease caused by insulin-binding antibodies in susceptible subjects. Insulin antibodies change glucose dynamics and could increase the incidence of hypoglycemic episodes. Detection of insulin antibodies is the diagnostic test. Changing therapeutic modalities reduced the incidence of hypoglycemic episodes.

Clinical and Laboratory Aspects of Insulin Autoantibody-Mediated Glycaemic Dysregulation and Hyperinsulinaemic Hypoglycaemia: Insulin Autoimmune Syndrome and Exogenous Insulin Antibody Syndrome

Autoimmune glycaemic dysregulation and hyperinsulinaemic hypoglycaemia mediated by insulin autoantibodies is an increasingly recognised but controversial phenomenon described in both exogenous insulin naïve (insulin autoimmune syndrome) and exposed (exogenous insulin antibody syndrome) individuals. There has been a significant proliferation of case reports, clinical studies and reviews in the medical literature in recent years which have collectively highlighted the discrepancy between experts in the field with regard to the nomenclature, definition, proposed pathophysiology, as well as the clinical and biochemical diagnostic criteria associated with the condition. The essential characteristics of the condition are glycaemic dysregulation manifesting as episodes of hyperglycaemia and unpredictable hyperinsulinaemic hypoglycaemia associated with high titres of endogenous antibodies to insulin. Although the hypoglycaemia is often life-threatening and initiation of targeted therapies critical, the diagnosis is often delayed and attributable to various factors including: the fact that existence of the condition is not universally accepted; the need to exclude surreptitious causes of hypoglycaemia; the diverse and often complex nature of the glycaemic dysregulation; and the challenge of diagnostic confirmation. Once confirmed, the available therapeutic options are expansive and the reported responses to these therapies have been variable. This review will focus on our evolving understanding, and the associated diagnostic challenges - both clinical and laboratory - of this complex condition.

Analysis of the clinical characteristics of insulin autoimmune syndrome induced by methimazole

WHAT IS KNOWN AND OBJECTIVE

The number of case reports of insulin autoimmune syndrome (IAS) induced by methimazole (MMI) is increasing. The purpose of this study is to explore the clinical characteristics and provide a scientific reference for clinical diagnosis, treatment and prevention.

METHODS

The literature on IAS cases and case series induced by MMI in Chinese and English was collected for retrospective analysis.

RESULTS AND DISCUSSION

A total of 106 patients (males 33, females 73) were described in the Chinese and English literature. The median age of patients with IAS induced by MMI was 37 years (range 15-76) occurring during both regular and irregular MMI therapy or after resumption of medication. The onset of symptoms occurred at night or early morning, within days in some and up to 6 months in others; the symptoms were neuropathic in 65.31% and related to the autonomic nervous system in 33.67%. Blood glucose concentration in samples presumably taken during the hypoglycaemic phase was 1.7 mmol/L (median; range 0.03-4.7); insulin concentrations were elevated ≥100 mU/L (ref range) and associated with low C-peptide levels (<10 μg/L; ref range). Tests for IgG insulin autoantibodies (IAA) were positive in 104 patients (98.02%) and negative in two patients (1.98%). The 75-g oral glucose tolerance test (OGTT) showed impaired glucose tolerance and diabetic curves. Pancreatic imaging was unremarkable on computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound. Withdrawal of MMI alone or with corticosteroid treatment reduced hypoglycaemic episodes within days to 3 months. IAA decreased and became negative in 3 months (median; range 1-12). Follow-up showed no recurrent hypoglycaemic episodes at 5 months (median; range 1-60).

WHAT IS NEW AND CONCLUSION

Methimazole-induced IAS is a clinically rare autoimmune disease with hypoglycaemia that occurs during medication treatment that should be treated promptly.

Management of Insulin Autoimmune Hypoglycaemia: Single-centre experience from Western India with systematic review of world literature

BACKGROUND

Awareness about Insulin Autoimmune Hypoglycaemia (IAH) and its management remains limited.

METHODOLOGY

We describe two cohorts: Cohort 1 (n = 7) included patients with IAH from a tertiary care centre in India and Cohort 2 (n = 294) included systematic review of published English literature from PubMed. They were compared with our insulinoma patients (n = 41).

RESULTS

Cohort 1 included seven female patients where two had drugs (carbimazole and thiocolchicoside) as triggering factors. Except for one patient requiring oral prednisolone, others had spontaneous remission. The unique features from our series are being first case series of IAH from India and reporting of second case of thiocolchicoside triggered IAH. Cohort 2 had 294 patients identified from 149 publications. Mean age was 54 ± 19 years. Thirty-five different triggers were identified from 160 cases. Antithyroid drugs were most common triggers in Japanese patients and most common HLA allele was DRB1*0406, while it was alpha-lipoic acid and HLA DRB1*0403 in non-Asians. Serum Insulin >100 µIU/mL and insulin to C-peptide molar ratio (ICMR) >0.25 had specificity of 100% and 97.5%, respectively, for IAH as compared to insulinoma. 56% patients had remission with complex carbohydrate diet and trigger removal while 43% required immunosuppressants. 70% achieved remission within 6 months.

CONCLUSIONS

Middle age remains most common age group. Sulfhydryl drugs are most common triggers. Serum Insulin >100 µIU/mL and ICMR > 0.25 in critical sample are good predictors for diagnosis of IAH, which needs to be confirmed by IAA. Conservative management with dietary modification and trigger removal usually suffices in majority. Rests need immunosuppressants.

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.

Enhancement of postprandial endogenous insulin secretion rather than exogenous insulin injection ameliorated insulin antibody-induced unstable diabetes: a case report

BACKGROUND

Insulin injection, especially with insulin analogs, occasionally induces the production of insulin antibodies with high binding capacity and low affinity, similar to the insulin autoantibodies characteristic of insulin autoimmune syndrome (IAS). Production of these "IAS-like" insulin antibodies causes marked glycemic fluctuations with postprandial hyperglycemia and fasting hypoglycemia.

CASE PRESENTATION

A 66-year-old man with a 27-year history of diabetes was admitted because of marked glycemic fluctuations. Human insulin treatment had been initiated at age 56, followed by multiple daily injections of insulin analogs 5 years later. After the initial year of insulin analog treatment, the patient began to experience frequent morning hypoglycemic attacks and day-time hyperglycemia. Marked hyperinsulinemia (4500 μU/mL) and high titers of insulin antibodies (80.4%) with high binding capacity and low affinity indicated that IAS-like insulin antibodies were causing severe glucose fluctuations. Altering insulin formulations (insulin aspart → regular human insulin→ insulin lispro) proved to be ineffective. After several therapeutic trials, cessation of exogenous insulin and addition of mitiglinide to liraglutide with voglibose finally attenuated glycemic fluctuations with increased postprandial insulin secretion. Continuous glucose monitoring revealed improvement of morning hypoglycemia and postprandial hyperglycemia with smaller mean amplitude of glycemic excursion. Therefore, compared to exogenously injected insulin, endogenously secreted insulin directly and rapidly acts on hepatocytes and suppresses postprandial glucose output.

CONCLUSIONS

Proper enhancement of postprandial endogenous insulin aimed at suppressing postprandial glucose output without stimulating excessive glucose uptake in the periphery is potentially useful for treating diabetes with insulin antibody-induced glycemic instability.

Spontaneously remitting insulin autoimmune syndrome in a patient taking alpha-lipoic acid

Insulin autoimmune syndrome (IAS), or Hirata disease, is a rare hypoglycaemic disorder caused by the presence of high titer of insulin autoantibodies (IAA) in patients without previous exposure to exogenous insulin. Even though its pathogenesis is not fully understood, striking evidences link IAS to previous exposure to sulphydryl-containing medications, like alpha-lipoic acid, a widely used nutritional supplement. Although challenging, a careful differential diagnosis from other causes of hyperinsulinaemic hypoglycaemia (such as insulinoma) is mandatory, since these conditions require different therapeutic approaches. In the present study, we report a 35-year-old woman originally from Sri Lanka who was referred to our University Hospital on suspicion of occult insulinoma. Her medical history was positive for endometriosis, treated with estroprogestins and alpha-lipoic acid. The latter supplement was begun 2 weeks before the first hypoglycaemic episode. Our tests confirmed the presence of hypoglycaemia associated with high insulin and C-peptide concentrations. When insulin concentrations were compared using different assays, the results were significantly different. Moreover, insulin values significantly decreased after precipitation with polyethylene glycol. An assay for IAA proved positive (530 U/mL). A genetic analysis revealed the presence of HLA-DRB1*04,15, an immunogenetic determinant associated with IAS. On the basis of clinical data we avoided a first-line approach with immunosuppressive treatments, and the patient was advised to modify her diet, with the introduction of frequent low-caloric meals. During follow-up evaluations, glucose levels (registered trough a flash glucose monitoring system) resulted progressively more stable. IAA titer progressively decreased, being undetectable by the fifteenth month, thus indicating the remission of the IAS. Learning points: Insulin autoimmune syndrome (IAS) is a rare cause of hyperinsulinaemic hypoglycaemia, whose prevalence is higher in East Asian populations due to the higher prevalence of specific immunogenetic determinants. Nevertheless, an increasing number of IAS cases is being reported worldwide, due to the wide diffusion of medications such as alpha-lipoic acid. Differential diagnosis of IAS from other causes of hyperinsulinemic hypoglycaemia is challenging. Even though many tests can be suggestive of IAS, the gold standard remains the detection of IAAs, despite that dedicated commercial kits are not widely available. The therapeutic approach to IAS is problematic. As a matter of fact IAS is often a self-remitting disease, but sometimes needs aggressive immunosuppression. The benefits and risks of any therapeutic choice should be carefully weighted and tailored on the single patient.

Insulin autoimmune syndrome in an occidental woman: a case report and literature review

Insulin autoimmune syndrome (IAS, Hirata's disease) is a rare hypoglycemic disorder characterized by spontaneous hypoglycemia associated with extremely high circulating insulin levels and positive anti-insulin antibody results. Thus far, most cases have been reported in Asian countries, notably Japan, with few cases reported in western countries. As a possible cause, it is associated with the use of drugs containing sulfhydryl radicals, such as captopril. This report refers to a 63-year-old female Brazilian patient with a history of postprandial hypoglycemia. After extensive investigation and exclusion of other causes, her hyperinsulinemic hypoglycemia was considered to have likely been induced by captopril. Most cases of IAS are self-limiting. However, dietary management, corticosteroids, plasmapheresis, and rituximab have already been used to treat patients with IAS. In our case, after discontinuation of captopril, an initial decrease in insulin autoantibody levels was observed followed by improvement in episodes of hypoglycemia. Although it is a rare disease, IAS should be considered in the differential diagnosis of endogenous hyperinsulinemic hypoglycemia. Patients with suspected IAS must be screened for autoimmunity-related drugs for insulin. Initial clinical suspicion of IAS can avoid unnecessary costs associated with imaging examinations and/or invasive surgical procedures.

Insulin autoimmune syndrome: from diagnosis to clinical management

Autoimmune forms of hypoglycemia are a rare cause of low blood sugar levels among Caucasians, and often go misdiagnosed, exposing patients to lengthy series of pointless, potentially harmful and expensive tests. There are two types of autoimmune hypoglycemia. One is insulin autoimmune syndrome (IAS), which is characterized by hyperinsulinemic hypoglycemia, elevated insulin autoantibody (IAA) titers, no prior exposure to exogenous insulin, and no of pathological abnormalities of the pancreatic islets. This condition is also known as "Hirata's disease". The other is type B insulin resistance syndrome (TBIRS), a rare autoimmune disorder resulting in a broad array of abnormalities in glucose homeostasis-from hypoglycemia to extremely insulin-resistant hyperglycemia-caused by the presence of insulin receptor autoantibodies (IRAbs). This review focuses on these two syndromes, describing their epidemiology, possible genetic background, clinical presentation, pathophysiology, diagnosis and treatment.

Potential cause-effect relationship between insulin autoimmune syndrome and alpha lipoic acid: Two case reports

OBJECTIVES

Insulin autoimmune syndrome (IAS) or Hirata disease is a rare cause of autoimmune hypoglycemia with apparent high insulin levels and anti-insulin autoantibodies and was first described by Hirata in Japan in 1970. IAS cases are usually related to exposure to sulfhydryl-containing drugs, which stimulate the production of insulin autoantibodies. Among sulfhydryl-containing compounds, alpha lipoic acid (ALA) has recently emerged as a cause of IAS. After the first observations of ALA-induced IAS were reported in Japan in 2006, an increasing number of cases related to ALA administration have been described. An Italian group recently reported on six cases of IAS of which one was associated with HLA-DRB1*04:06 and the remaining five with HLA-DRB1*04:03. This suggests that the latter is potentially involved in the genetic susceptibility of people of European descent to IAS.

METHODS

Here, we describe two new cases of IAS in women that were triggered by ALA.

RESULTS

Both cases are associated with HLA-DRB1*04:03 and confirm the evidence that HLA-DRB1*04:03 rather than HLA-DRB1*04:06 is specifically related to IAS susceptibility in Europeans.

CONCLUSIONS

Case reports of ALA-induced hypoglycemic episodes highlight the need for greater care in prescribing ALA supplementation as well as the identification of specific and personalized therapeutic targets.

"Riding High on Low Fuel" - Our Experience with Endogenous Hyperinsulinemic Hypoglycemia

INTRODUCTION

Endogenous hyperinsulinemic hypoglycemia (EHH) is a condition in which the insulin levels are inappropriately high in the presence of low plasma glucose.

MATERIALS AND METHODS

We did a retrospective analysis of case records of those patients admitted and evaluated for EHH from June 2004 to June 2016 in our center, excluding those that were diagnosed with reactive hypoglycemia. We collected data regarding demographics, clinical presentation, laboratory results, localization techniques, and treatment administered.

RESULTS

Sixteen patients who were admitted for evaluation based on history suggestive of repeated hypoglycemic episodes were included in the study. All but one pregnant patient was subjected to a supervised fast in the hospital. All patients developed hypoglycemia (defined using Whipple's triad) within the first 24 h. Three patients had autoimmune hypoglycemia which differed significantly from insulinoma-mediated hypoglycemia in certain clinical and laboratory parameters. They were older in age with marked fluctuations in the 24 h glucose profile ranging from frank hypoglycemia to frank hyperglycemia. The insulin levels were markedly elevated in this group of patients along with a significantly elevated insulin C peptide molar ratio (ICMR) when compared with patients with insulinoma-mediated hypoglycemia.

CONCLUSIONS

Although insulinoma is the most common cause of EHH, autoimmune hypoglycemia should be considered as a differential diagnosis, particularly in older individuals with plasma glucose values increasing to the hyperglycemic range. Degree of elevation of insulin levels and ICMR may provide additional clues. Overall, the survival and prognosis of patients with EHH are excellent.

Clopidogrel-Induced Insulin Autoimmune Syndrome: A Newly Recognized Cause of Hypoglycemia in a Patient Without Diabetes

Insulin autoimmune syndrome (IAS), defined as hyperinsulinemic hypoglycemia with high titers of anti-insulin antibodies, is frequently reported in Japanese patients but rarely observed in whites. We report in this study on a 79-year-old white male without diabetes who developed IAS following exposure to clopidogrel, a drug not previously known to cause hypoglycemia. The patient presented with recurrent symptomatic hypoglycemia. During one episode, serum glucose was 45 mg/dL, whereas insulin and C-peptide levels were 40,000 mIU/mL and 40 ng/mL, respectively. Additional studies revealed no intake of insulin or its secretagogues, whereas anti-insulin antibody titer was high (59.3 nmol/L). Although total insulin levels were consistently high, free insulin concentrations (polyethylene glycol precipitation) were appropriate for ambient glycemia. The patient was found to have HLA-DRB1*0404, a feature often reported in Japanese patients with IAS. Three weeks prior to symptom onset, he was started on clopidogrel, a drug that does not have a sulfhydryl group, but its active metabolite does. Clopidogrel was switched to a nonsulfhydryl antiplatelet agent, and glucocorticoid therapy was initiated. Shortly thereafter, the frequency of hypoglycemic episodes decreased, and glucocorticoids were tapered over the ensuing 3 months. No hypoglycemic episodes were noted during 6 months of observation after discontinuing glucocorticoids, whereas the total insulin and anti-insulin antibody levels normalized. The data indicate that IAS should be considered in the differential diagnosis of hyperinsulinemic hypoglycemia in seemingly well individuals, even when no drugs known to cause IAS were used. Clinical suspicion of IAS can avoid expensive imaging and unnecessary surgery in affected patients.

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.

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.

Rare association of insulin autoimmune syndrome with ankylosing spondylitis

Insulin autoimmune syndrome (IAS) is a rare cause of hyperinsulinemic hypoglycaemia, which is known to occur in association with the use of sulfhydryl-containing drugs and autoimmune disorders. We describe a patient with hitherto an unreported association of IAS with ankylosing spondylitis. We have also performed and described a simplified method of polyethylene glycol (PEG) precipitation of an insulin bound antibody in the serum.

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.

Insulin autoimmune syndrome (Hirata Disease) in European Caucasians taking α-lipoic acid

OBJECTIVE

Lipoic acid (LA) is a widely used nutritional supplement and is sometimes used as an adjuvant treatment for diabetic neuropathy and other conditions. Insulin autoimmune syndrome (IAS, Hirata disease) is a rare cause of spontaneous hypoglycaemia, extremely high serum insulin levels and high titres of autoantibodies against endogenous insulin despite no prior exposure to exogenous insulin. In Japanese individuals, IAS is associated with the human leucocyte antigen (HLA) HLA-DRB1*04:06 allele and often occurs upon exposure to sulphhydryl-containing compounds including LA. Only one case has been reported in Caucasians. We now report six Caucasian patients taking LA with IAS and describe a unique HLA subtype in these patients.

RESEARCH DESIGN AND METHODS

Six Caucasian patients (M = 3; F = 3), median age 63 years, presented with spontaneous episodes of fasting and postabsorptive hypoglycaemia associated with mainly neuroglycopenic symptoms. No patient was treated with insulin or had an insulinoma. Hypoglycaemic symptoms appeared 30 and 120 days after taking lipoic acid (LA; 600 mg/day). Case histories and standard laboratory analyses were utilized.

RESULTS

Discontinuation of LA resulted in a reduction in hypoglycaemic episodes. All patients were treated with oral or iv glucose and prednisone (12.5-25 mg/day). HLA analysis revealed the HLA-DRB1*04:03 allele in five patients, while the HLA-DRB1*04:06 allele was present in one patient.

CONCLUSIONS

This is the first report of LA-related IAS in Caucasians who possess the HLA-DRB1*04:03 allele, implicating this allele in the genetic susceptibility to IAS in Caucasians. The greater occurrence of the HLA-DRB1*04:03 allele in Caucasian and other populations, combined with the growing use of LA in developed countries, may be a future predictor of additional cases of IAS.

Relapsing and remitting severe hypoglycemia due to a monoclonal anti-insulin antibody heralding a case of multiple myeloma

CONTEXT

We report a novel case of insulin autoimmune syndrome (IAS) presenting with hypoglycemia due to production of a monoclonal anti-insulin antibody in a patient subsequently found to have multiple myeloma (MM).

OBJECTIVE

The aim of the study was to describe the 5-yr clinical course of a patient with IAS and MM and to characterize the origin and function of the pathogenic antibody.

METHODS

We conducted a longitudinal case history with laboratory investigations to characterize the anti-insulin antibody subtype, specificity, affinity, and origin.

RESULTS

The patient presented with IAS, which worsened during treatment of hepatitis C. The patient was then discovered to have a monoclonal gammopathy that progressed to MM. Treatment of the MM induced remission of the neoplasia and IAS, which then followed a synchronized course of progression and response to therapy. An anti-insulin IgG(3)-λ that bound specifically but with low affinity to the insulin B chain (amino acids 9-30) and that was distinct from the primary MM IgG(3)-κ clone was recovered from the patient and cloned. The antibody bound insulin and showed mutations of normal affinity maturation.

CONCLUSIONS

We describe a case of MM heralded by IAS, where full characterization of the pathogenic antibody revealed that the monoclonal anti-insulin antibody had originated from a self-reactive clone.

Etiopathogenesis of insulin autoimmunity

Autoimmunity against pancreatic islet beta cells is strongly associated with proinsulin, insulin, or both. The insulin autoreactivity is particularly pronounced in children with young age at onset of type 1 diabetes. Possible mechanisms for (pro)insulin autoimmunity may involve beta-cell destruction resulting in proinsulin peptide presentation on HLA-DR-DQ Class II molecules in pancreatic draining lymphnodes. Recent data on proinsulin peptide binding to type 1 diabetes-associated HLA-DQ2 and -DQ8 is reviewed and illustrated by molecular modeling. The importance of the cellular immune reaction involving cytotoxic CD8-positive T cells to kill beta cells through Class I MHC is discussed along with speculations of the possible role of B lymphocytes in presenting the proinsulin autoantigen over and over again through insulin-carrying insulin autoantibodies. In contrast to autoantibodies against other islet autoantigens such as GAD65, IA-2, and ZnT8 transporters, it has not been possible yet to standardize the insulin autoantibody test. As islet autoantibodies predict type 1 diabetes, it is imperative to clarify the mechanisms of insulin autoimmunity.

[Antitumor effects of raddeanin A on S180, H22 and U14 cell xenografts in mice]

BACKGROUND & OBJECTIVE

Raddeanin A, a triterpenoid saponin from Anemone raddeana Regel, has good antitumor activity in vitro. This study was to investigate its antitumor effects on tumor cell xenografts in mice.

METHODS

The inhibitory effects of raddeanin A on the proliferation of human nasopharyngeal carcinoma KB cells and ovarian cancer SKOV3 cells were measured by MTT assay. The inhibitory effects of raddeanin A injection on the growth of sarcoma S180, liver cancer H22 and cervical carcinoma U14 cell xenografts in mice and the effect of raddeanin A lavage on the growth of S180 cell xenografts were measured. The acute toxicity of raddeanin A was also measured.

RESULTS

The 50% inhibition concentration (IC(50)) of raddeanin A was 4.64 microg/mL for KB cells and 1.40 microg/mL for SKOV3 cells. When injected with raddeanin A at a dose of 4.5 mg/kg, the growth inhibition rates of S180, H22 and U14 cell xenografts were 60.5%, 36.2% and 61.8%, respectively. When lavaged with raddeanin A at a dose of 200 mg/kg, the growth inhibition rate of S180 cell xenografts was 64.7%. The median lethal dose (LD50) of raddeanin A lavage was 1.1 g/kg and that of raddeanin A injection was 16.1 mg/kg.

CONCLUSION

Raddeanin A has good antitumor activity both in vitro and in vivo, and would be a potential antitumor medicine.

Severe insulin resistance due to anti-insulin antibodies: response to plasma exchange and immunosuppressive therapy

Anti-insulin antibodies have been described in two contexts: in insulin-naive individuals (so-called 'insulin autoimmune syndrome') and in patients with insulin-treated diabetes, in whom antibodies are rarely of clinical significance. We report the case of an 68-year-old woman who exhibited a local allergic reaction to subcutaneous insulin followed by severe insulin resistance, evidenced by poor glycaemic control despite treatment with > 3.5 U/kg of insulin per day. She was found to have circulating polyclonal anti-insulin antibodies of the IgG subtype and responded clinically to a course of plasma exchange and immunosuppression with mycophenolate mofetil and, subsequently, intravenous immunoglobulin. Falling titres of antibodies on this regimen correlated with improved glycaemic control. This case suggests that clinicians should be alert to the possibility of insulin resistance due to anti-insulin antibodies and that immunosuppression in this situation may be a valuable therapeutic option.

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.

Acute liver dysfunction complicated with uncontrollable glycemia due to insulin antibody: successful treatment with glucocorticoid and lispro insulin

Here, we report a case of acute liver dysfunction complicated with uncontrollable glycemia due to insulin antibody. The patient was admitted to our hospital due to diabetic ketoacidosis. He was administered insulin immediately, however, his fasting plasma glucose level remained unstable despite the insulin treatment. Blood biochemistry revealed severe liver dysfunction, although no markers including hepatitis virus or autoantibodies associated with autoimmune liver diseases were detected. The 125I-insulin binding rate was high (54%). The characteristics of insulin antibody in this patient were similar to the antibodies of IAS patients, therefore we administered oral glucocorticoid against insulin antibody. The reduction in the 125I-insulin binding rate and the binding capacity of the high affinity site of insulin antibodies were balanced after oral glucocorticoid therapy. In addition, preprandial subcutaneous regular insulin was switched to lispro insulin. Postprandial plasma glucose levels were relatively improved by lispro insulin. The etiology of acute liver dysfunction was unknown, however, we believe that the combination of oral glucocorticoid and lispro insulin was suitable and useful for preventing recurrent liver dysfunction in this patient.

Antibody response to inhaled insulin in patients with type 1 or type 2 diabetes. An analysis of initial phase II and III inhaled insulin (Exubera) trials and a two-year extension trial

OBJECTIVE

To compare antibody responses to inhaled human insulin vs. sc human insulin and to determine whether insulin antibody binding is associated with adverse clinical consequences.

RESEARCH DESIGN AND METHODS

Insulin antibody data from initial phase II/III trials were analyzed comparing the efficacy and safety of inhaled insulin with various agents, including sc insulin. Additionally, data from a 24-month extension of the phase III studies were examined. Data were pooled into the following three groups based on insulin treatment status at baseline: patients with type 1 diabetes, and patients with type 2 diabetes using insulin and not using insulin at baseline. Ig class analysis was also performed on randomly selected sera from type 1 patients at the end of the initial trials.

RESULTS

In the initial trials, greater insulin antibody binding was observed in patients receiving inhaled insulin vs. sc insulin. The greatest antibody responses to inhaled insulin were observed in patients with type 1 diabetes [nonparametric comparison of medians at the end of the study, 22.0% binding (unadjusted 95% confidence interval: 19.5, 24.5)], and the lowest responses were observed in non-insulin-using patients with type 2 diabetes in which there was no difference in median values at the end of the study. There were no correlations between antibody binding and glycemic control (measured using glycosylated hemoglobin), insulin dose requirements, hypoglycemic events, or pulmonary function (measured by changes in forced expiratory volume in 1 sec and diffusion capacity of carbon monoxide). Antibody responses were IgG in type. Differences in antibody levels observed in patients with type 1 vs. type 2 diabetes were maintained over the 24-month extension trials. Peak antibody levels across all groups were generally observed after 6-12 months of insulin therapy. Inhaled insulin therapy was not associated with a greater incidence of allergy or other hypersensitivity reactions.

CONCLUSION

Inhaled insulin was observed to produce a larger antibody response than sc insulin. Insulin antibody binding has not been associated with adverse clinical consequences in trials to date.

Severe hypoglycemic coma due to insulin autoimmune syndrome

Insulin autoimmune syndrome, characterized by the presence of insulin-binding autoantibodies and fasting or late postprandial hypoglycemia, is a rare cause of hypoglycemia. We report a patient with pulmonary tuberculosis who developed recurrent spontaneously post-absorptive hyperinsulinemic hypoglycemia after treatment with anti-tuberculous drugs. Imaging studies of the pancreas were unremarkable, and selective intra-arterial calcium stimulation with hepatic venous sampling for insulin failed to show a gradient, thus almost completely excluding the possibility of occult insulinoma or nesidioblastosis. Examinations of sera, however, disclosed a high titer of polyclonal insulin-binding autoantibodies containing at least 2 classes of binding sites, 1 with high affinity but low capacity, and the other with low affinity but high capacity. An oral glucose tolerance test revealed high serum levels of total insulin associated with relatively low levels of free insulin, but not of C-peptide, suggesting binding of the released insulin to autoantibodies. Regretfully, shortly after the withdrawal of isoniazid, the patient died of respiratory failure unrelated to hypoglycemia, and whether these antibodies were induced by isoniazid remains unknown. We recommend that insulin autoimmune syndrome be one of the differential diagnoses in patients with hyperinsulinemic hypoglycemia.

A trial to assess the amount of insulin antibodies in diabetic patients by surface plasmon resonance

OBJECTIVE

To measure the amount and affinity of insulin antibodies, we performed a trial to establish a new method for quantitative and qualitative analysis of these antibodies by using surface plasmon resonance (BIAcore system).

METHODS

Real-time detection of insulin antibody interaction and kinetic analysis were performed using the BIAcore system.

PATIENTS OR MATERIALS

Eight diabetic patients with insulin antibodies and whose fasting total immunoreactive insulin levels were more than 100 microU/ml were selected. The patients with and without recurrent hypoglycemia were classified into hypoglycemic episode-positive or hypoglycemic episode-negative groups, respectively. Seven diabetic patients without insulin antibodies were selected as controls.

RESULTS

In the 8 patients, the concentration of insulin antibodies ranged from 2.91 to 16.3 microg/ml and insulin antibodies were not detected in the control group. The apparent KD (dissociation constant) and kd (the dissociation rate constant) values of the patients were much larger than those seen for the anti-human insulin monoclonal antibody. The KD values were significantly higher in the hypoglycemic episode-positive group than in the hypoglycemic episode-negative group (p<0.05). No significant differences in the concentration, the ka (the association rate constant) and the kd values were noted between the groups.

CONCLUSION

The data suggests that insulin antibodies of the patients have an apparently lower affinity status in sera as compared with that for the anti-human insulin monoclonal antibody, and dissociate easily from the immune-complex in the sera, especially in cases where there is recurrent hypoglycemia in the patients. Therefore insulin antibody characteristics are one of the causative factors in hypoglycemic episodes.

Severe Autoimmune Hypoglycemia With Insulin Antibodies Necessitating Plasmapheresis

OBJECTIVE

To report a case of autoimmune hypoglycemia.

METHODS

We describe the clinical course of a patient with autoimmune hypoglycemia, including results of biochemical and histocompatibility antigen studies, as well as the therapeutic intervention and follow-up.

RESULTS

A 77-year-old man presented with clinical manifestations of severe spontaneous hypoglycemia associated with extremely high levels of insulin (>300 mU/mL) and insulin antibodies (>100 U/mL) without any exogenous insulin administration. He had no other associated autoimmune disorder or exposure to the sulfhydryl group of drugs. Corticosteroid therapy was initiated, but the patient continued to have hypoglycemia and required plasmapheresis. The hypoglycemia resolved after plasmapheresis. During follow-up, the patient was treated with prednisone, the dose of which was tapered gradually. The insulin antibodies, which had decreased rapidly after plasmapheresis, gradually disappeared within a few months. The patient remained free of hypoglycemia as well as insulin antibodies 11 months after corticosteroid therapy was discontinued.

CONCLUSION

Although autoimmune hypoglycemia is an uncommon disorder, it should be considered in any patient with hypoglycemia in the setting of nonsuppressed insulin levels associated with insulin antibodies.

The use of phage display to distinguish insulin autoantibody (IAA) from insulin antibody (IA) idiotypes

AIM/HYPOTHESIS

Radiobinding assays (RBA) are unable to differentiate insulin autoantibodies (IAA) from insulin antibodies (IA). We sought to establish whether random peptide phage display might generate reagents with which to distinguish IAA idiotopes from IA idiotopes.

METHODS

Two insulin-binding sera were used to select phagotopes from a phage library. The first, designated IAS, came from an insulin-treated patient with the insulin autoimmune syndrome, and was known to contain both IA and a high titre of human insulin specific (B30 threonine dependent) IAA. The second, designated IDD, was taken from a newly-diagnosed IAA(+) Type 1 diabetic patient. Phage colonies selected by insulin-purified IgG extracts of IAS and IDD were selected at random for DNA sequencing, and tested for their reactivity with insulin antibodies and ability to distinguish disease-associated idiotopes.

RESULTS

Seven phagotopes bound IAS and the phagotope designated IAS-9, corresponding to sequence KRSRLDV, gave the highest binding standard deviation (SD) score. Seven phagotopes bound IDD and the phagotope designated IDD-10, corresponding to sequence LGRGGSK, bound most strongly. IAS-9 was able to displace insulin binding in IAS and all of ten insulin-treated Type 2 diabetic patients, but not the IAA present in any of the eight patients with newly-diagnosed Type 1 diabetes. IDD-10, on the other hand, could displace insulin binding detected in the sera of eight patients with untreated Type 1 diabetes (IAA), but not in IAS or sera of the insulin-treated Type 2 diabetics.

CONCLUSION

Phagotopes provide reagents which between them can distinguish positively as well as negatively diabetes-associated IAA from non-diabetes associated IAA and from IA.

Insulin autoantibodies and insulin antibodies have similar binding characteristics

Type 1 diabetes is an autoimmune disease characterized by immune-mediated destruction of the pancreatic beta cells. Insulin autoantibodies (IAAs) develop in many subjects at high risk for developing type 1 diabetes prior to onset of clinical disease and exposure to exogenous insulin, whereas insulin antibodies (IAs) commonly develop in patients treated with exogenous insulin. To investigate whether the binding characteristics of IAA and IA are similar, we measured eight different binding characteristics of IAAs from 19 insulin-naive first-degree relatives of type 1 diabetes patients and compared these to the binding characteristics of IAs from 19 type 1 diabetes patients treated with exogenous insulin. IAA and IA samples were matched for percentage insulin binding. Scatchard analysis revealed that IAAs have a two-slope representation similar to IAs-that is, two populations of antibodies, a high-affinity low-capacity population and a low-affinity high-capacity population. Binding properties of the two respective populations were found to be similar for IAAs and IAs. Sipps' equation was used to generate a Hill plot and produce an index of heterogeneity, which showed further similarity between IAAs and IAs. These results suggest that the IAAs found in subjects at increased risk for type 1 diabetes, like IAs, are likely to be polyclonal in nature. The similarities between IAAs and IAs support the hypothesis that both are induced by insulin presentation to the immune system.

Imaging of the buffering effect of insulin antibodies in the autoimmune hypoglycemic syndrome

Insulin autoimmune hypoglycemia is characterized by recurrent hypoglycemia and high levels of immunoreactive insulin in the presence of insulin autoantibodies. The mechanisms inducing hypoglycemia are largely unknown. An [123I]insulin scintigraphic scanning was performed to directly demonstrate the effect of antibodies on insulin biodistribution in one patient with this syndrome both before and after treatment. The patient had insulin autoantibodies IgG3 lambda, which had a single site dissociation constant (Kd = 10(-7) mol/L, by Scatchard analysis), a very fast dissociation rate of immune complexes, and a very rapid association of [125I]insulin. Insulin receptors on red blood cells were down-regulated. The [123I]insulin scintigraphic study imaged the buffering effect of antibodies on insulin bioavailability. [123I]Insulin was not removed from the blood, and no liver or kidney uptake of the hormone occurred. The frequency and severity of hypoglycemic episodes required treatment. Insulin antibody levels decreased and [123I]insulin biodistribution improved after treatment with plasmapheresis and prednisone. Improved hormone bioavailability was further evidenced by the reduction in the hypoglycemic delay after i.v. insulin from 90 min before any treatment to 60 min after plasmapheresis and 30 min after steroid administration. Glucose tolerance was normal after treatment. Plasmapheresis followed by steroid treatment can lower the insulin antibody concentration, abolish severe hypoglycemia, and improve insulin biodistribution and glucose tolerance in insulin autoimmune hypoglycemia.