Recognition and management of drug-induced cytopenias: the example of idiosyncratic drug-induced thrombocytopenia

Scientific premise for the involvement of neutrophil extracellular traps (NETs) in vaccine-induced thrombotic thrombocytopenia (VITT)

Following on from the devastating spread of COVID‐19, a major global priority has been the production, procurement, and distribution of effective vaccines to ensure that the global pandemic reaches an end. However, concerns were raised about worrying side effects, particularly the occurrence of thrombosis and thrombocytopenia after administration of the Oxford/AstraZeneca and Johnson & Johnson's Janssen COVID‐19 vaccine, in a phenomenon being termed vaccine‐induced thrombotic thrombocytopenia (VITT). Similar to heparin‐induced thrombocytopenia (HIT), this condition has been associated with the development of anti‐platelet factor 4 antibodies, purportedly leading to neutrophil‐platelet aggregate formation. Although thrombosis has also been a common association with COVID‐19, the precise molecular mechanisms governing its occurrence are yet to be established. Recently, increasing evidence highlights the NLRP3 (NOD‐like, leucine‐rich repeat domains, and pyrin domain‐containing protein) inflammasome complex along with IL‐1β and effete neutrophils producing neutrophil extracellular traps (NETs) through NETosis. Herein, we propose and discuss that perhaps the incidence of VITT may be due to inflammatory reactions mediated via IL‐1β/NLRP3 inflammasome activation and consequent overproduction of NETs, where similar autoimmune mechanisms are observed in HIT. We also discuss avenues by which such modalities could be treated to prevent the occurrence of adverse events and ensure vaccine rollouts remain safe and on target to end the current pandemic.

The Emerging Role of the Innate Immune Response in Idiosyncratic Drug Reactions

Idiosyncratic drug reactions (IDRs) range from relatively common, mild reactions to rarer, potentially life-threatening adverse effects that pose significant risks to both human health and successful drug discovery. Most frequently, IDRs target the liver, skin, and blood or bone marrow. Clinical data indicate that most IDRs are mediated by an adaptive immune response against drug-modified proteins, formed when chemically reactive species of a drug bind to self-proteins, making them appear foreign to the immune system. Although much emphasis has been placed on characterizing the clinical presentation of IDRs and noting implicated drugs, limited research has focused on the mechanisms preceding the manifestations of these severe responses. Therefore, we propose that to address the knowledge gap between drug administration and onset of a severe IDR, more research is required to understand IDR-initiating mechanisms; namely, the role of the innate immune response. In this review, we outline the immune processes involved from neoantigen formation to the result of the formation of the immunologic synapse and suggest that this framework be applied to IDR research. Using four drugs associated with severe IDRs as examples (amoxicillin, amodiaquine, clozapine, and nevirapine), we also summarize clinical and animal model data that are supportive of an early innate immune response. Finally, we discuss how understanding the early steps in innate immune activation in the development of an adaptive IDR will be fundamental in risk assessment during drug development. SIGNIFICANCE STATEMENT: Although there is some understanding that certain adaptive immune mechanisms are involved in the development of idiosyncratic drug reactions, the early phase of these immune responses remains largely uncharacterized. The presented framework refocuses the investigation of IDR pathogenesis from severe clinical manifestations to the initiating innate immune mechanisms that, in contrast, may be quite mild or clinically silent. A comprehensive understanding of these early influences on IDR onset is crucial for accurate risk prediction, IDR prevention, and therapeutic intervention.

High-Throughput Sequencing to Investigate Associations Between HLA Genes and Metamizole-Induced Agranulocytosis

Background and Objective: Agranulocytosis is a rare and potentially life-threatening complication of metamizole (dipyrone) intake that is characterized by a loss of circulating neutrophil granulocytes. While the mechanism underlying this adverse drug reaction is not well understood, involvement of the immune system has been suggested. In addition, associations between genetic variants in the Human Leukocyte Antigen (HLA) region and agranulocytosis induced by other drugs have been reported. The aim of the present study was to assess whether genetic variants in classical HLA genes are associated with the susceptibility to metamizole-induced agranulocytosis (MIA) in a European population by targeted resequencing of eight HLA genes.

Design: A case-control cohort of Swiss patients with a history of neutropenia or agranulocytosis associated with metamizole exposure (n = 53), metamizole-tolerant (n = 39) and unexposed controls (n = 161) was recruited for this study. A high-throughput resequencing (HTS) and high-resolution typing method was used to sequence and analyze eight HLA loci in a discovery subset of this cohort (n = 31 cases, n = 38 controls). Identified candidate alleles were investigated in the full Swiss cohort as well as in two independent cohorts from Germany and Spain using HLA imputation from genome-wide SNP array data. In addition, variant calling based on HTS data was performed in the discovery subset for the class I genes HLA-A, -B, and -C using the HLA-specific mapper hla-mapper.

Results: Eight candidate alleles (p < 0.05) were identified in the discovery subset, of which HLA-C^∗04:01 was associated with MIA in the full Swiss cohort (p < 0.01) restricted to agranulocytosis (ANC < 0.5 × 10⁹/L) cases. However, no candidate allele showed a consistent association in the Swiss, German and Spanish cohorts. Analysis of individual sequence variants in class I genes produced consistent results with HLA typing but did not reveal additional small nucleotide variants associated with MIA.

Conclusion: Our results do not support an HLA-restricted T cell-mediated immune mechanism for MIA. However, we established an efficient high-resolution (three-field) eight-locus HTS HLA resequencing method to interrogate the HLA region and demonstrated the feasibility of its application to pharmacogenetic studies.

Pathophysiology and Diagnosis of Drug-Induced Immune Thrombocytopenia

Drug-induced immune thrombocytopenia (DITP) is a life-threatening clinical syndrome that is under-recognized and difficult to diagnose. Many drugs can cause immune-mediated thrombocytopenia, but the most commonly implicated are abciximab, carbamazepine, ceftriaxone, eptifibatide, heparin, ibuprofen, mirtazapine, oxaliplatin, penicillin, quinine, quinidine, rifampicin, suramin, tirofiban, trimethoprim-sulfamethoxazole, and vancomycin. Several different mechanisms have been identified in typical DITP, which is most commonly characterized by severe thrombocytopenia due to clearance and/or destruction of platelets sensitized by a drug-dependent antibody. Patients with typical DITP usually bleed when symptomatic, and biological confirmation of the diagnosis is often difficult because detection of drug-dependent antibodies (DDabs) in the patient’s serum or plasma is frequently not possible. This is in contrast to heparin-induced thrombocytopenia (HIT), which is a particular DITP caused in most cases by heparin-dependent antibodies specific for platelet factor 4, which can strongly activate platelets in vitro and in vivo, explaining why affected patients usually have thrombotic complications but do not bleed. In addition, laboratory tests are readily available to diagnose HIT, unlike the methods used to detect DDabs associated with other DITP that are mostly reserved for laboratories specialized in platelet immunology.

Platelet antibodies in immune thrombocytopenia and related conditions

Platelet autoantibodies are a common finding in immune thrombocytopenia (ITP) and in rare cases of antibody-mediated platelet function (“acquired thrombasthenia”). In drug-induced immune thrombocytopenia, antibodies react with platelets only in the presence of the offending drug. Alloantibodies reacting with platelets are induced by transfusion of cellular blood products or during pregnancy. They are responsible for fetal/neonatal alloimmune thrombocytopenia (FNAIT), they are able to cause febrile, nonhemolytic transfusion reactions and they give rise to insufficient platelet increments following platelet transfusions. Two rare transfusion reactions: post-transfusion purpura (PTP) and passive alloimmune thrombocytopenia (PAT) are triggered by platelet alloantibodies. This review discusses the clinical value of tests for platelet antibodies in various clinical situations related to insufficient primary hemostasis.

Metamizole-associated neutropenia: Comparison of patients with neutropenia and metamizole-tolerant patients

Reports of metamizole-induced neutropenia have increased in Switzerland and Germany over the last decades, most likely reflecting increased use of metamizole. To date, there are no effective strategies to identify patients at increased risk of metamizole-induced neutropenia. In this observational, multi-center comparative study, characteristics of patients with metamizole-associated neutropenia were compared with patients treated with metamizole without developing adverse hematological reactions. Patients with metamizole-induced neutropenia treated at the University Hospitals Basel and Bern between 2005 and 2017 were included. Tolerant comparison patients with continuous metamizole treatment (≥500 mg/day for at least 28 days) were recruited from GP offices and community pharmacies. Forty-eight patients with metamizole-induced neutropenia, consisting of 23 and 25 cases with inpatient-acquired and outpatient-acquired neutropenia, respectively, were compared to 39 metamizole tolerant comparison patients. Median latency until first diagnosis of neutropenia was 6 days (1-61 days) in inpatient cases and 19 days (2-204 days) in outpatient cases. There was no association between non-myelotoxic and non-immunosuppressive co-medication (p = .6627), history of drug allergy (p = .1304), and preexisting auto-immune diseases (p = .2313) and the development of metamizole-induced neutropenia. Our results suggest that autoimmune diseases, history of drug allergy, and concomitant treatment with non-myelotoxic and non-immunosuppressive drugs are likely not individual risk factors for metamizole-associated neutropenia.

Treatment effectiveness of levamisole plus prednisolone on oral lichen planus patients with emphasis on levamisole-induced agranulocytosis or pancytopenia

BACKGROUND/PURPOSE

Physicians' and dentists' knowledge of levamisole-induced agranulocytosis or pancytopenia remains incomplete. This study aimed to evaluate the treatment effectiveness of levamisole plus prednisolone on oral lichen planus (OLP) patients with emphasis on levamisole-induced hematological changes.

METHODS

Ninety patients with erosive OLP were given 120 mg/day new levamisole (Levazol) and 15 mg/day prednisolone for three consecutive days each week. Three cases with levamisole-induced blood-cytopenias were assessed and treated within one year.

RESULTS

Most patients reported significant pain relief and showed no evidence of erosive OLP after 4-8 weeks of treatment with few side effects; nevertheless, three female patients developed agranulocytosis or granulocytopenia with concomitant thrombocytopenia or pancytopenia within 2-6 weeks after levamisole (Levazol) treatment. One case with previously unknown double episodes of agranulocytosis revealed her first episode following interruption of levamisole (Decaris) treatment for 4 months. High fever and sore throat were the most common symptoms, but two agranulocytosis cases remained asymptomatic one week before diagnosis, and were treated with levamisole withdrawal and empiric antimicrobial initiation as well as utilization of granulocyte colony-stimulating factors. Neutrophil recovery took about 1 week, but over 4 weeks in one of the cases (an elderly patient) with septic shock.

CONCLUSION

Agranulocytosis or pancytopenia usually developed within 2 months after levamisole treatment, but it might be delayed. Agranulocytosis was more likely to occur in females and onset was acute. Levamisole is an effective immunomodulator for OLP patients; however, it should be used with caution and administered with regular blood monitoring.

Non-chemotherapy drug-induced neutropenia - an update

INTRODUCTION

To date, non-chemotherapy drug-induced severe neutropenia (neutrophil count of ≤0.5 x 10⁹/L) also called idiosyncratic drug-induced agranulocytosis is little discussed in the literature. In the present paper, we report and discuss the clinical data and management of this rare disorder. Areas covered: To do this, we carried out a review of the literature using PubMed database of the US National Library of Medicine. We also used data from the American Society of Hematology educational books, textbooks of Hematology and Internal medicine, and information gleaned from international meetings. Expert opinion: Idiosyncratic agranulocytosis remains a potentially serious adverse event due to the frequency of severe sepsis with severe deep tissue infections (e.g., pneumonia), septicemia, and septic shock in approximately two-thirds of all hospitalized patients. In this context, several prognostic factors have been identified that may be helpful when identifying 'susceptible' patients. Old age (>65 years), septicemia or shock, renal failure, and a neutrophil count ≤0.1 × 10⁹/L have been consensually accepted as poor prognostic factors. In our experience, modern management with pre-established procedures, intravenous broad-spectrum antibiotics and hematopoietic growth factors (particularly G-CSF) is likely to improve the prognosis. Thus with appropriate management, the mortality rate is currently between 5 to 10%.

A patient with agranulocytosis following the discontinuation of methimazole treatment for 4 months: A case report

Agranulocytosis is a rare and serious adverse effect of antithyroid drugs (ATD), in particular methimazole (MMI), and usually develops within 3 months following the start of uninterrupted ATD treatment. Agranulocytosis may also develop for the first time following interruption and subsequent resumption of the same ATD treatment. In this case report, a 27-year-old female, who was treated for thyrotoxicosis with MMI, developed agranulocytosis following the discontinuation of MMI treatment for four months. To the best of our knowledge, this is the first study to report this. The aim of this report is to increase the awareness of physicians of the onset of agranulocytosis when MMI is discontinued, and to demonstrate that MMI should be used with caution.

Drug-Induced Thrombocytopenia in the Critically Ill

Background:Drugs are suspected when obvious causes of intensive care unit (ICU)-acquired thrombocytopenia have been excluded. It has been estimated that 10% to 25% of cases may be drug induced. Objectives: The objectives of this study were to evaluate the risk of thrombocytopenia associated with drug classes commonly used in the ICU. Methods: Data concerning patients admitted for more than 48 hours between 1997 and 2011 were extracted from a research-purpose database. Patients with thrombocytopenia within the first 72 hours of admission and with diagnoses or interventions considered strongly associated with thrombocytopenia were excluded. Drug exposures were compared and adjusted for confounders using conditional logistic regression. Results: A total of 238 cases were identified after exclusions. Each case was matched according to sex, age, admission year, and admission unit with 1 control. In univariate analysis, quinolones (odds ratio [OR] = 1.56; 95% CI = 1.01-2.40) and extended spectrum β-lactams (OR = 1.71; 95% CI = 1.00-2.93) were significantly associated with an increased risk of thrombocytopenia. After adjusting for confounders, exposure to quinolones was the only drug class with a statistically significant increase in risk of thrombocytopenia (OR = 1.697; 95% CI = 1.002-2.873; P = 0.049). Conclusion: In this study of ICU-acquired thrombocytopenia, we found no association between the exposures to several antibiotic classes, anticonvulsants, antiplatelet agents, nonsteroidal anti-inflammatory agents, and heparins and thrombocytopenia. As linezolid was not studied, no conclusions can be drawn concerning this agent. The statistically significant association between quinolones and thrombocytopenia warrants further investigation.

Assessment of a modified 4T scoring system for heparin-induced thrombocytopenia in critically ill patients

PURPOSE

The purpose of the study is to determine if a modified 4T (m4T) scoring system, which omits clinical evaluation of other thrombocytopenic etiologies, is different from the 4T scoring system's probability to predict a positive heparin-induced thrombocytopenia (HIT) laboratory test in the intensive care unit.

MATERIALS AND METHODS

This is a single-centered retrospective analysis of critically ill adults who had an enzyme-linked immunosorbent assay antiplatelet factor 4 antibody (ELISA anti-PF4 Ab) ordered. Patients were identified as HIT positive (optical density, ≥0.40) or HIT negative (optical density, <0.40) based on the ELISA anti-PF4 Ab. Both 4T and m4T scores were calculated, and the diagnostic accuracy was compared using paired receiver operating characteristic curves.

RESULTS

A total of 1487 adult intensive care unit patients with an ELISA anti-PF4 Ab ordered between January 2007 and December 2009 were eligible for study enrollment. Application of exclusion criteria and random selection yielded a total of 232 patients included for analysis (58 HIT-positive and 174 HIT-negative patients). The area under the curve for the 4T and m4T scores were 0.683 (95% confidence interval, 0.604-0.762) and 0.680 (95% confidence interval, 0.600-0.759), respectively (P=.065).

CONCLUSION

This study does not show a difference in the probability of the m4T and 4T scoring systems to predict a positive ELISA anti-PF4 Ab test in the critically ill patient population. Further prospective studies are needed to validate the m4T scoring system.

Only severe thrombocytopenia results in bleeding and defective thrombus formation in mice

Hemostasis, thrombosis, and ischemic brain infarction efficiently occur at unexpectedly low platelet counts in mice. The threshold platelet count required for occlusive thrombus formation differs between thrombosis models.

Review article: non-malignant haematological complications of anti-tumour necrosis factor alpha therapy

BACKGROUND

Tumour necrosis factor-alpha (TNF-α) is an important mediator of the molecular cascade leading to chronic inflammation. TNF-α inhibitors have proven their safety and efficacy in the treatment of inflammatory diseases.

AIM

To review the non-malignant haematological adverse events, such as thrombocytopaenia, neutropaenia, hypercoagulability, pancytopaenia and aplastic anaemia in patients receiving TNF-α inhibitors.

METHODS

We reviewed the literature by searching MEDLINE and EMBASE databases as well as references of all retrieved articles for the following terms: anti-tumour necrosis factor, anti-TNF, infliximab, adalimumab, certolizumab, etanercept, haematological complications, thrombocytopaenia, neutropaenia, anaemia, bone marrow and thrombosis.

RESULTS

Thombocytopaenia is a very rare phenomenon and was associated with no serious adverse events. However, transient neutropaenia developed in up to 16% of cases. Patients with a previous history of neutropaenia on other therapies or baseline neutrophil count <4 × 10(9) /L are at a particularly higher risk. The association between anti-TNF-α therapy and thrombosis is very nebulous due to the multitude of potential confounders. Only one case of primary eosinophilia has been reported with anti-TNF-α therapy.

CONCLUSION

Regular monitoring of the white blood cell count at baseline and with each infusion is recommended for patients on anti-TNF-α. Further studies to elucidate their interaction with the immune system are warranted.

Clinical presentation and management of drug-induced agranulocytosis

OBJECTIVE

In this article, we report and discuss the clinical presentation and management of idiosyncratic drug-induced agranulocytosis (neutrophil count <0.5 × 10(9)/l).

RESULTS/CONCLUSIONS

Idiosyncratic drug-induced agranulocytosis remains a potentially serious adverse event owing to the frequency of severe sepsis with severe deep tissue infections (e.g., pneumonia), septicemia and septic shock in approximately two-thirds of all hospitalized patients. However, several prognostic factors have recently been identified that may be helpful in practice to identify 'susceptible' patients. Old age (>65 years), septicemia or shock, metabolic disorders such as renal failure and a neutrophil count below 0.1 × 10(9)/l are currently consensually accepted as poor prognostic factors. In this potentially life-threatening disorder, modern management with broad-spectrum antibiotics and hematopoietic growth factors (particularly granulocyte colony-stimulating factor) is likely to improve prognosis. Thus, with appropriate management, the mortality rate from idiosyncratic drug-induced agranulocytosis is currently approximately 5%.

Drug-induced thrombocytopenia in critically ill patients

Thrombocytopenia occurs in 15% to 58% of intensive care unit patients. The incidence varies based upon patient population, timing and frequency of platelet monitoring, and definition of thrombocytopenia. Up to 25% of acutely ill patients develop drug-induced thrombocytopenia. When drug-induced thrombocytopenia is suspected, nondrug related causes must be evaluated and excluded. Establishing the diagnosis of drug-induced thrombocytopenia is challenging, as hundreds of medications have been implicated. Medications commonly associated with drug-induced thrombocytopenia include glycoprotein IIb/IIIa inhibitors, cinchona alkaloids, antibiotics, anticonvulsants, and heparin. Once the diagnosis is suspected, clinicians should identify the start date of medications to assess the timeline of development. The likelihood of each medication causing thrombocytopenia must be evaluated. The risk vs. benefit of discontinuing the suspected medication and availability of alternative medications must be assessed. The role of corticosteroids, immune globulin, and plasmapheresis is uncertain. Once the offending agent has been discontinued, the overall prognosis is excellent. In the case of suspected or confirmed heparin-induced thrombocytopenia, an alternative anticoagulant should be initiated. Drug-induced thrombocytopenia should be documented in the medical record and reported according to institutional and national standards. This review focuses on immune-mediated drug-induced thrombocytopenia from medications commonly utilized in the critically ill patient.