Lymphocyte subpopulations: a potential predictor of a response in patients with immune thrombocytopenia

OBJECTIVES

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder caused by increased platelet destruction and altered production. Despite the well-described pathophysiological background of immune dysregulation, current treatment guidelines consist of monotherapy with different drugs, with no tool to predict which patient is more suitable for each therapeutic modality.

METHODS

In our study, we attempted to determine differences in the immune setting, comparing the patients' responses to administered therapy. During 12-month follow-up, we assessed blood count, antiplatelet autoantibodies, and T lymphocyte subsets in peripheral blood in 35 patients with ITP (newly diagnosed or relapsed disease).

RESULTS

Our data show that the value of antiplatelet autoantibodies, the percentage of cytotoxic T lymphocytes, and the immunoregulatory index (IRI, CD4+ / CD8+ T cell ratio) differ significantly by treatment response. Responders have a higher IRI (median 2.1 vs. 1.5 in non-responders, P = 0.04), higher antiplatelet autoantibodies (median 58 vs. 20% in non-responders, P = 0.01) and lower relative CD8+ T cells count (P = 0.02) before treatment.

DISCUSSION

The results suggest that immunological parameters (antiplatelet autoantibodies, relative CD8+ T cell count and IRI) could be used as prognostic tools for a worse clinical outcome in patients with ITP.

CONCLUSION

These biomarkers could be utilized for stratification and eventually selection of treatment preferring combination therapy.

The evolution of preexisting primary immune thrombocytopenia after COVID-19 onset: A nationally representative, prospective, multicentre, observational study

The symptoms in patients with primary immune thrombocytopenia (ITP) after COVID-19 onset remain largely unclear. The aim of this study was to describe the platelet count fluctuations in ITP patients following the diagnosis of COVID-19. A prospective multicentre observational study was conducted from December 15th, 2022, to January 31st, 2023 in 39 general hospitals across China. Patients with preexisting primary ITP who were newly diagnosed with COVID-19 were enrolled. A total of 1216 ITP patients with newly-diagnosed COVID-19 were enrolled. 375 (30.8%) patients experienced ITP exacerbation within eight weeks after the diagnosis of COVID-19, and most exacerbation (266/375, 70.9%) developed in the first two weeks. Immunosuppressive therapy for ITP and severe/critical COVID-19 infection were independent variables associated with ITP exacerbation. Overall the platelet count had a transient increasing trend, and the platelet peak value occurred at two weeks after COVID-19 infection. Then, the platelet count decreased to the baseline level in the following weeks. The platelet count had a transient increasing trend in ITP patients following the diagnosis of COVID-19. ITP exacerbation only occurred in less than one-third of ITP patients. Nonimmunosuppressive therapy may have an advantage to prevent ITP exacerbation during COVID-19.

Acute primary CMV infection complicated by pneumonitis and ITP in young immunocompetent woman in a regional Queensland Hospital

We present the first published case of simultaneous pneumonitis and immune thrombocytopenic purpura secondary to primary cytomegalovirus (CMV) infection in an immunocompetent patient. Treatment with oral valganciclovir for 2 weeks successfully led to complete clinical recovery. CMV is traditionally associated with infection in immunocompromised patients and neonates; however, evidence of severe CMV infections in immunocompetent hosts is emerging. It is important to highlight the broad range of clinical presentations of CMV infections to prevent diagnostic delay and associated morbidity and expense.

Machine learning models developed and internally validated for predicting chronicity in pediatric immune thrombocytopenia

BACKGROUND

Primary immune thrombocytopenia (ITP) in children is typically self-limiting; however, 20% to 30% of patients may experience prolonged thrombocytopenia lasting over a year. The challenge is predicting chronicity to ensure personalized treatment approaches.

OBJECTIVES

To address this issue, we developed and internally validated 4 machine learning (ML) models using demographic and immunologic characteristics to predict the likelihood of chronicity.

METHODS

The present study was conducted at Beijing Children's Hospital from June 2018 to December 2021, aiming to develop predictive models for determining the chronicity of pediatric ITP. Four ML models, based on a logistic regression classifier, random forest classifier, eXtreme Gradient Boosting (XGBoost), and support vector machine, were employed. These models used a set of 16 variables, including 14 immunologic and 2 demographic predictors. The performance evaluation criteria included prediction accuracy, precision, recall, F1 score, and area under the receiver operating characteristic curve (AUROC).

RESULTS

Data were collected from 662 patients who were randomly assigned to either a training dataset or a testing dataset using a random number generator. Among them, 26.5% had chronic disease. All models performed well, with AUROC values ranging from 0.81 to 0.84, and XGBoost was selected for its highest AUROC score and interpretability in constructing the predictive model. Age, T helper 17, T helper 17-to-regulatory T cell ratio, T helper 1, and double-negative T cells were identified as significant predictors by the XGBoost algorithm.

CONCLUSION

We developed a precise predictive model for chronicity in pediatric ITP using ML during the initial phase. The XGBoost model achieved high predictive accuracy by using individual patient clinical parameters and demonstrated commendable interpretability.

Risk-based and individualised management of bleeding and thrombotic events in adults with primary immune thrombocytopenia (ITP)

Although bleeding is one of the main symptoms of primary immune thrombocytopenia (ITP), risk factors for bleeding have yet to be fully established. Low platelet count (PC; <20-30 × 109 /L) is generally indicative of increased risk of bleeding. However, PC and bleeding events cannot be fully correlated; many other patient- and disease-related factors are thought to contribute to increased bleeding risk. Furthermore, even though ITP patients have thrombocytopenia and are at increased risk of bleeding, ITP also carries higher risk of thrombotic events. Factors like older age and certain ITP treatments are associated with increased thrombotic risk. Women's health in ITP requires particular attention concerning haemorrhagic and thrombotic complications. Management of bleeding/thrombotic risk, and eventually antithrombotic therapies in ITP patients, should be based on individual risk profiles, using a tailored, patient-centric approach. Currently, evidence-based recommendations and validated tools are lacking to support decision-making and help clinicians weigh risk of bleeding against thrombosis. Moreover, evidence is lacking about optimal PC for achieving haemostasis in invasive procedures settings. Further research is needed to fully define risk factors for each event, enabling development of comprehensive risk stratification approaches. This review discusses risk-based and individualised management of bleeding and thrombosis risk in adults with primary ITP.

Successful treatment of coexisting membranous nephropathy and immune thrombocytopenia by eradicating gastric Helicobacter pylori infection: a case report

Membranous nephropathy (MN) is a common cause of nephrotic syndrome in middle-aged and older adults. MN etiology is mainly primary or idiopathic; however, it may also be secondary to infections, drugs, neoplasms, and autoimmune diseases. We present the case of a 52-year-old Japanese man with coexisting nephrotic MN and immune thrombocytopenic purpura (ITP). Renal biopsy revealed glomerular basement membrane thickening with immunoglobulin (Ig) G and complement component 3 deposition. Glomerular IgG subclass analysis revealed predominant IgG4 deposition with weak IgG1 and IgG2 deposition. IgG3 and phospholipase A2 receptor deposits were negative. Upper endoscopy revealed no ulcers, but histological examination demonstrated Helicobacter pylori infection in the gastric mucosa with elevated IgG antibodies. After gastric Helicobacter pylori eradication, the nephrotic-range proteinuria and thrombocytopenia of the patient were markedly improved without initiation of immunosuppressive treatment. Therefore, clinicians should consider the possibility of Helicobacter pylori infection in patients with coexisting MN and ITP. Further studies are required to demonstrate the associated pathophysiological aspects.

Evaluation of vitamin D status in adult patients with newly diagnosed immune thrombocytopenia

It has been shown that 25-OH vitamin D not only preserves calcium and bone homeostasis but also has immunomodulatory effects. The purpose of this study was to assess the association between adult patients with recently diagnosed immune thrombocytopenia (ITP) and vitamin D levels. Retrospective technique was employed in this study. The associations between 25(OH)D value and platelet count, as well as the clinical symptoms of ITP upon diagnosis and 25(OH)D value, were our main findings. A total of 60 patients diagnosed and followed up in our clinic were included in the study. Forty-one patients (68.3%) were female and 19 (31.7%) were male. The median age of the patients was 52.5 (19-88). The median vitamin D level of all patients at diagnosis of ITP was 11.5 (3-86). There was no statistically significant difference between the patients divided into three groups according to their vitamin D levels, in terms of laboratory parameters. There was no statistically significant difference in clinical findings according to vitamin D status in ITP patients. There was no statistically significant difference in terms of relapse-free survival in all three groups (p = 0.71). In conclusion, in our study, no correlation was found between laboratory and clinical findings at diagnosis and vitamin D levels in adult ITP patients. Additional investigations, particularly randomized controlled trials, are required to examine the relationship between 25(OH)D and the incidence and severity of ITP.

Immune thrombocytopenia (ITP) in pregnancy

Immune thrombocytopenia (ITP) in pregnancy is challenging for both mother and fetus. Understanding the pathophysiology, treatments, and risks to the mother and fetus leads to proper management resulting in successful pregnancy and delivery in almost all cases.1 ITP in a pregnant woman has many similarities to ITP not in pregnancy although gestational thrombocytopenia can be confused with ITP. However, recognizing differences is instrumental in avoiding bleeding complications and toxicities of treatment. This Nutshell review focuses on the natural history of ITP in pregnancy, its treatment, and dilemmas.

Prednisone vs high-dose dexamethasone in newly diagnosed adult primary immune thrombocytopenia: a randomized trial

ABSTRACT

A debate exists regarding which type of corticosteroids (standard-dose prednisone [PDN] or high-dose dexamethasone [HD-DXM]) is the best first-line treatment for adult patients with newly diagnosed untreated primary immune thrombocytopenia (pITP). An ad hoc study compared PDN with HD-DXM in newly diagnosed untreated patients with pITP (aged ≥18 but ≤80 years, platelet count of ≤20 or >20 but <50 × 109/L, and bleeding score of ≥8). Patients were randomised to receive PDN 1 mg/kg per day from days 0 to 28 (Arm A) or HD-DXM 40 mg per day for 4 days, every 14 days, for 3 consecutive courses (Arm B). Fifty-nine of 113 patients (52.2%) were randomized to Arm A and 54 of 113 (47.8%) to Arm B. In evaluable patients, total initial responses (complete response [CR], partial response [PR], minimal response [MR]) were 44 of 56 (78.57%) in Arm A and 46 of 49 (93.88%) in Arm B at days 42 and 46, respectively (P = 0.0284). Total final responses (at day 180 from initial response) were 26 of 43 (60.47%) in Arm A and 23 of 39 (58.97%) in Arm B (P = 0.8907). Total persistent responses (at 12 months from initial response) were 25 of 31 (80.65%) in Arm A and 20 of 36 (55.56%) in Arm B (P = 0.0292). Seven relapses occurred. Median follow-up was 44.4 months. Overall survival was 100% at 48 months, overall disease-free survival was 81.11% at 48 months from day 180. PDN and pulsed HD-DXM were well tolerated; HD-DXM allows effective initial responses but less long lasting than PDN. This trial was registered at www.clinicaltrials.gov as #NCT00657410.

A prospective cohort study to identify clinical diagnostic and prognostic markers of primary immune thrombocytopenia in dogs

BACKGROUND

Primary immune thrombocytopenia (pITP) in dogs presents a diagnostic challenge, and clinical markers of severity are lacking.

OBJECTIVES

Identify clinicopathologic features that differentiate pITP from secondary ITP (sITP) and markers related to bleeding severity, transfusion, and survival of dogs with pITP.

ANIMALS

Ninety-eight thrombocytopenic dogs (58 pITP and 40 sITP).

METHODS

Client-owned dogs with platelet counts <50 000/μL were enrolled in a prospective, multi-institution cohort study. History and treatment information, through a maximum of 7 days, was recorded on standard data forms. Bleeding severity was scored daily using a bleeding assessment tool (DOGiBAT). At-admission blood samples were collected for CBC, biochemistry, C-reactive protein concentration, and coagulation panels, and to measure platelet surface-associated immunoglobulin G (PSAIg) and expression of platelet membrane proteins and phospholipids. Dogs with evidence of coincident disease were classified as sITP.

RESULTS

No definitive pITP diagnostic test was found. However, pITP cases were characterized by lower platelet counts, D dimer concentrations, and platelet membrane protein expression than sITP cases. Differentiation between pITP and sITP was further enhanced using logistic regression modeling combining patient sex, coagulation profile, platelet count, D dimer, and PSAIg. A second model of pITP severity indicated that low hematocrit and high BUN concentration were associated with non-survival. Low hematocrit at admission, but not platelet count or DOGiBAT score, was associated with transfusion.

CONCLUSIONS AND CLINICAL IMPORTANCE

Pending validation studies, models constructed from at-admission clinicopathologic findings may improve differentiation of pITP from sITP and identify the most severe pITP cases at the time of presentation.

Association Between Idiopathic Thrombocytopenic Purpura and Hemorrhagic and Nonhemorrhagic Stroke

BACKGROUND

Idiopathic thrombocytopenic purpura (ITP) is characterized by a low platelet count. This may lead to an increased risk of hemorrhagic stroke but a lower rate of nonhemorrhagic stroke. The goal of this study was to evaluate the association between ITP and both hemorrhagic and nonhemorrhagic strokes using a large database.

METHODS

We used the Nationwide Inpatient Sample (NIS) database to analyze the occurrence of hemorrhagic and nonhemorrhagic stroke in patients with and without a diagnosis of ITP from 2005 to 2014.

RESULTS

Univariate analysis revealed a higher incidence of hemorrhagic stroke in patients with ITP in the year studied. (for example, in 2005: OR, 1.75; 95% CI, 1.57-1.94; P < 0.001; 2014: OR, 2.19; 95% CI, 2.03-2.36; P < 0.001). After adjusting for age, gender, race, and hypertension, hemorrhagic stroke remained significantly associated with ITP (in 2005: OR, 1.85; 95% CI, 1.49-1.89; P < 0.001; 2014: OR, 2.01; 95% CI, 1.86-2.18; P < 0.001) for all the years studied. Nonhemorrhagic stroke occurred at a lower rate in patients with ITP in most years (2006: OR, 0.91; 95% CI, 0.85-0.97; P = 0.004; 2014: OR, 0.88; 95% CI, 0.83-0.93; P < 0.001). Multivariate analysis confirmed a higher rate of nonhemorrhagic stroke in ITP patients.

CONCLUSION

Our analysis showed that there was a higher rate of hemorrhagic stroke but a lower rate of ischemic stroke in ITP patients, suggesting an important role of platelets in the occurrence of stroke.

Is Immune Thrombocytopenia and its Treatment Associated with Sarcopenia?

BACKGROUND

Immune thrombocytopenia (ITP) is defined as an isolated platelet count less than 100 × 109/L in the absence of other causes of thrombocytopenia. Sarcopenia is a body-wide muscular disorder with a progressive nature that leads to reduced mobility, physical disability, falls, and poor quality of life. We aimed to evaluate the frequency of objectively diagnosed sarcopenia in patients with ITP and to determine whether ITP therapies have sarcopenic effects.

METHODS

This prospective study included patients who were followed up with ITP in the hematology outpatient clinic. Patients who had received corticosteroids within 3 months were excluded. The handgrip strength test, appendicular skeletal muscle mass (ASMM), ASMM/height2 value, soft lean mass (SLM), trunk soft lean mass (SLMT), and the 6-min walking speed test were applied for muscular evaluations and physical performance assessment.

RESULTS

We included 53 patients (female/male: 73.58%/26.42%). While sarcopenia was not observed in 77.36% of ITP patients, possible sarcopenia was diagnosed in 9.43% and confirmed sarcopenia in 13.21%. Severe sarcopenia was not seen in any of the patients. Loss of muscle strength was observed in 22.64% of patients. SLM was found to be low in 92.45%.

CONCLUSION

Sarcopenia may be more frequent among patients with ITP compared to the population, and it is important to note that 92.45% of patients had low SLM and 54.72% had low SLMT. Eltrombopag therapy might be beneficial as demonstrated by higher SLM, ASMM, and ASMM/height2 values.

How I diagnose and treat thrombocytopenia in geriatric patients

ABSTRACT

Thrombocytopenia in older individuals is a common but diagnostically challenging condition that has variable clinical impact to those who are affected. Diagnostic approach requires evaluation of the preexisting clinical conditions, detailed review of medications, and assessment for disorders that warrant urgent treatment. In this article, we describe a systematic approach to diagnosis of thrombocytopenia and present a schematic review for management strategies. Three clinical scenarios are presented that are relevant for their prevalence and management challenges in an older adult population. The first scenario addresses primary immune thrombocytopenia (ITP) and reviews different treatment options. The second one addresses complications of thrombocytopenia in management of the myelodysplastic syndrome. The last one reviews diagnostic challenges of drug-induced ITP.

Hematology in the post-COVID era: spotlight on vaccine-induced immune thrombotic thrombocytopenia and a conceptual framework (the 4P's) for anti-PF4 diseases

INTRODUCTION

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a life-threatening prothrombotic disorder first identified following the introduction of adenoviral vector vaccines for COVID-19. The condition is characterized by anti-PF4 antibodies and clinically presents with thrombocytopenia and thrombosis often in unusual anatomical sites.

AREAS COVERED

In this review, we discuss the clinical presentation, diagnostic testing, and treatment of VITT. We also review VITT-like syndromes that have been described in patients without previous vaccination. We propose a conceptual framework for the mechanism of anti-PF4 diseases that includes sufficiently high levels of PF4, the presence of a Polyanion that can form immune complexes with PF4, a Pro-inflammatory milieu, and an immunological Predisposition - the 4Ps.

EXPERT OPINION

Significant progress has been made in understanding the characteristics of the VITT antibody and in testing methods that can confirm that diagnosis. Future work should be directed at understanding long-term outcomes, mechanisms of thrombosis, and individual risk factors for this rare but dangerous immune-thrombotic disease.

Conspicuous Peripheral Retinal Hemorrhages with a Relatively Preserved Posterior Pole in Immune Thrombocytopenic Purpura

BACKGROUND

Immune thrombocytopenic purpura (ITP) is a rare auto-antibody mediated disease of isolated thrombocytopenia (<100,000/μL) with normal haemoglobin levels and leukocyte counts. Only a small number of ITP cases have been reported with accompanying ophthalmological findings. Herein, we report an ITP case with demonstrative retinal haemorrhages.

CASE PRESENTATION

A fifty-five-year-old woman with a known history of type 2 diabetes mellitus was referred to our clinic with blurred vision. After detailed anamnesis and clinical assessment, she was diagnosed as primary ITP in haematology department, and systemic steroid (1.5mg/kg) therapy was initiated. During her follow-up, a concomitant peripheral facial paralysis (PFP) emerged. In the course of follow-up, her platelet counts increased gradually, the retinal haemorrhages regressed partially, and the PFP recovered completely.

CONCLUSION

ITP is a rare haematologic disease that sometimes manifests with additional systemic involvements, and this disease should be remembered in the differential diagnosis of unusual retinal haemorrhages, which might be the only presenting feature.

Successful treatment with belimumab for immune thrombocytopenia associated with systemic lupus erythematosus: A report of two cases

Immune thrombocytopenia (ITP) is a common complication of systemic lupus erythematosus (SLE). Glucocorticoids (GCs) and hydroxychloroquine are first-line therapy for SLE-associated ITP (SLE-ITP). SLE-ITP in most of patients is less severe and well controlled with GCs, but some of the patients are GC resistant and require additional immunosuppressants including calcineurin inhibitors, azathioprine, and rituximab. We present two cases of SLE-ITP patients treated with belimumab who were resistant to GCs and achieved remission. For severe SLE-ITP, belimumab has emerged as a novel induction therapeutic option.

Autoimmune Cytopenias Are Highly Associated with Inborn Errors of Immunity and They May Be the Initial Presentations in Cases without Severe Infections

INTRODUCTION

Inborn errors of immunity (IEIs) are inherited disorders that present with increased susceptibility to infections as well as noninfectious complications. Due to the aberrant immune functions of patients with IEI, autoimmune cytopenia (AIC) may be the initial finding, which makes diagnosis a challenge. We aimed to evaluate the clinical course, laboratory findings, and treatment response of AIC in children with IEI.

METHODS

Data of children with autoimmune hemolytic anemia (AIHA) and/or immune thrombocytopenic purpura (ITP) were obtained from a retrospective chart review of IEI patients diagnosed and followed in our center. Demographic and clinical features and therapeutic outcomes were evaluated. Immunologic findings were compared between patients with AIHA, ITP, and Evans syndrome (ES). The patients were also divided into two subgroups based on the presence or absence of immune dysregulation diseases (IDDs), and all data were compared between these two groups.

RESULTS

Out of 562 patients with IEI, 6% (n: 34) had AIC which were ITP (23.5%), AIHA (35.5%), and ES (41.2%). AIC was the initial finding in 50% of these 34 patients. Patients with ES had a higher mean percentage of CD8+ T lymphocytes than ITP patients (40.77 ± 20.21% vs. 22.33 ± 12.48%, p = 0.011). Patients with IDDs were more likely to develop ES (p = 0.004), lymphoproliferation (p = 0.005), and resistance to first-line therapy (p = 0.021) than other IEI groups.

CONCLUSION

This study shows that AIC may be the initial finding of IEI, particularly when lymphoproliferation and resistance to first-line therapy co-occur. Therefore, detailed investigation should be offered to all patients to avoid diagnostic delay.

Predicting the efficacy of glucocorticoids in pediatric primary immune thrombocytopenia using plasma proteomics

Objective

Primary immune thrombocytopenia (ITP) is the most common acquired autoimmune bleeding disorder among children. While glucocorticoids are the primary first-line treatment for ITP treatment, they prove ineffective in certain patients. The challenge of identifying biomarkers capable of early prediction regarding the response to glucocorticoid therapy in ITP persists. This study aimed to identify ideal biomarkers for predicting glucocorticoid efficacy in patients with ITP using plasma proteomics.

Methods

A four-dimensional data-independent acquisition approach was performed to determine the differentially expressed proteins in plasma samples collected from glucocorticoid-sensitive (GCS) (n=18) and glucocorticoid-resistant (GCR) (n=17) children with ITP treated with prednisone. The significantly differentially expressed proteins were selected for enzyme-linked immunosorbent assay validation in a cohort conprising 65 samples(30 healthy controls, 18 GCS and 17 GCR children with ITP). Receiver operating characteristics curves, calibration curves, and clinical decision curve analysis were used to determine the diagnostic efficacy of this method.

Results

47 differentially expressed proteins (36 up-regulated and 11 down-regulated) were identified in the GCR group compared with the GCS group. The significantly differentially expressed proteins myosin heavy chain 9 (MYH9) and fetuin B (FETUB) were selected for enzyme-linked immunosorbent assay validation. The validation results were consistent with the proteomics analyses. Compared with the GCS group, the GCR group exhibited a significantly reduced the plasma concentration of MYH9 and elevated the plasma concentration of FETUB. Furthermore, the receiver operating characteristics curves, calibration curves, and clinical decision curve analysis demonstrated good diagnostic efficacy of these validated biomarkers.

Conclusion

This study contributes to the establishment of objective biological indicators for precision therapy in children with ITP. More importantly, the proteins MYH9 and FETUB hold potential as a foundation for making informed decisions regarding alternative treatments for drugresistant patients, thereby preventing treatment delays.

Where have all the platelets gone? HIT, DIC, or something else?

Thrombocytopenia in ill children is common; accurately diagnosing the underlying etiology is challenging and essential for appropriate management. Triggers for accelerated consumption of platelets are numerous; common downstream mechanisms of clearance include platelet trapping in microvascular thrombi, phagocytosis, and platelet activation. Thrombocytopenia with microangiopathic hemolytic anemia (MAHA) is frequently due to disseminated intravascular coagulation. Thrombotic microangiopathy (TMA) is a subgroup of MAHA. Specific TMA syndromes include thrombotic thrombocytopenic purpura, complement-mediated TMA (CM-TMA), and Shiga toxin-mediated hemolytic uremic syndrome. Isolated thrombocytopenia is characteristic of immune thrombocytopenia; however, concomitant cytopenias are frequent in critically ill patients, making the diagnosis difficult. Immune thrombocytopenia with large vessel thrombosis is a feature of heparin-induced thrombocytopenia and antiphospholipid antibody syndrome. In addition, thrombocytopenia is common with macrophage activation, which is characteristic of hemophagocytic lymphohistiocytosis. While thrombocytopenia in ill patients can be driven by hypoproliferative processes such as myelosuppression and/or bone marrow failure, this review will focus on consumptive thrombocytopenia due to immune and nonimmune causes.

How to manage ITP with life-threatening bleeding

While immune thrombocytopenia often presents with mild bleeding manifestations or surprising findings of thrombocytopenia on routine complete blood counts in patients without symptoms, some patients can present with new thrombocytopenia and life-threatening bleeding. Emergent assessment and treatment are needed to prevent substantial morbidity and even mortality. These patients present to the emergency room with bleeding, and hematologists are subsequently consulted. Understanding the approach to making the diagnosis and excluding other life-threatening illnesses is essential, as is rapid initiation of treatment in the bleeding patient even when the diagnosis of immune- mediated thrombocytopenia is tentative. Using a case-based format, we review how to approach and treat patients presenting with new thrombocytopenia and bleeding.

Thrombotic anti-PF4 immune disorders: HIT, VITT, and beyond

Antibodies against the chemokine platelet factor 4 (PF4) occur often, but only those that activate platelets induce severe prothrombotic disorders with associated thrombocytopenia. Heparin-induced thrombocytopenia (HIT) is the prototypic anti-PF4 disorder, mediated by strong activation of platelets through their FcγIIa (immunoglobulin G [IgG]) receptors (FcγRIIa). Concomitant pancellular activation (monocytes, neutrophils, endothelium) triggers thromboinflammation with a high risk for venous and arterial thrombosis. The classic concept of HIT is that anti-PF4/heparin IgG, recognizing antigen sites on (cationic) PF4 that form in the presence of (anionic) heparin, constitute the heparin-dependent antibodies that cause HIT. Accordingly, HIT is managed by anticoagulation with a nonheparin anticoagulant. In 2021, adenovirus vector COVID-19 vaccines triggered the rare adverse effect "vaccine-induced immune thrombotic thrombocytopenia" (VITT), also caused by anti-PF4 IgG. VITT is a predominantly heparin-independent platelet-activating disorder that requires both therapeutic-dose anticoagulation and inhibition of FcγRIIa-mediated platelet activation by high-dose intravenous immunoglobulin (IVIG). HIT and VITT antibodies bind to different epitopes on PF4; new immunoassays can differentiate between these distinct HIT-like and VITT-like antibodies. These studies indicate that (1) severe, atypical presentations of HIT ("autoimmune HIT") are associated with both HIT-like (heparin-dependent) and VITT-like (heparin-independent) anti-PF4 antibodies; (2) in some patients with severe acute (and sometimes chronic, recurrent) thrombosis, VITT-like antibodies can be identified independent of proximate heparin exposure or vaccination. We propose to classify anti-PF4 antibodies as type 1 (nonpathogenic, non- platelet activating), type 2 (heparin dependent, platelet activating), and type 3 (heparin independent, platelet activating). A key concept is that type 3 antibodies (autoimmune HIT, VITT) require anticoagulation plus an adjunct treatment, namely high-dose IVIG, to deescalate the severe anti-PF4 IgG-mediated hypercoagulability state.

Immune Thrombotic Thrombocytopenic Purpura in Elderly Patients: The Roles of PLASMIC and French Scores

Objective

In recent years, new developments have been incorporated into daily practice in the management of immune thrombotic thrombocytopenic purpura (iTTP). In particular, clinical scoring systems could help clinicians with clinical decision-making and early recognition. However, older patients frequently present with more organ involvement and in unusual ways. The ways in which age could affect these clinical prediction scoring systems remain unclear. We evaluated the use of PLASMIC and French scores in patients over 60 years of age.

Materials and Methods

We performed a retrospective cross-sectional analysis of patients over 60 years of age with a presumptive diagnosis of iTTP between 2014 and 2022 at 10 centers. We calculated PLASMIC and French scores and compared our data with a single-center analysis of younger patients presenting with thrombotic microangiopathy.

Results

Our study included 30 patients over 60 years of age and a control group of 28 patients younger than 60 years. The diagnostic sensitivity and specificity of a French score of ≥1 were lower in older patients compared to the control group (78.9% vs. 100% and 18.2% vs. 57.1%, respectively). The diagnostic sensitivity and specificity of a PLASMIC score of ≥5 were 100% vs. 95% and 27.3% vs. 100% for the study group and control group, respectively. Our study showed a higher mortality rate in older patients compared to the control group (30% vs. 7.1%, p=0.043).

Conclusion

For a limited number of patients (n=6), our results showed that rituximab can reduce mortality. Given that the reliability of clinical prediction scores for iTTP in older patients may be lower, more caution must be undertaken in interpreting their results.

Immune thrombotic thrombocytopenic purpura in patients over 60 years of age: Diagnostic pitfalls and treatment strategy

Real-world registry studies of older patients with iTTP highlight diagnostic difficulties in comparison to patients less than 60 years of age with greater risk of renal injury, atypical neurological features and less profound cytopenia, which can result in diagnostic delays. However, there is no clear signal of significantly increased toxicity from full active treatment. Commentary on: Gómez-Seguí et al. Immune thrombotic thrombocytopenic purpura in older patients: results from the Spanish TTP Registry (REPTT). Br J Haematol 2023;203:860-871.

Analysis of clinical characteristics and treatment efficacy in two pediatric cases of ANKRD26-related thrombocytopenia

ANKRD26-related thrombocytopenia (ANKRD26-RT or THC2, MIM 188 000), an autosomal dominant thrombocytopenia, is unresponsive to immunosuppressive therapy and susceptible to hematological malignancies. A large number of pediatric patients are diagnosed with immune thrombocytopenia (ITP) every year; however, thrombocytopenia of genetic origin is often missed. Extensive characterization of ANKRD26-RT will help prevent missed diagnosis and misdiagnosis. Furthermore, identification of ANKRD26-RT will help in the formulation of an accurate diagnosis and a treatment plan. In our study, we report cases of two Chinese pediatric patients with ANKRD26-RT and analyze their clinical characteristics, gene mutations, and treatment modalities. Both patients were 1-year-old and presented with mild bleeding (World Health Organization(WHO) score grade 1), different degrees of platelet reduction, normal mean platelet volume, and megakaryocyte maturation impairment not obvious. Genetic tests revealed that both patients had ANKRD26 gene mutations.Patient 1 had a mutation c.-140C>G of the 5' untranslated region (UTR), and patient 2 had a mutation of c.-127A>T of 5'UTR. Both patients were treated with eltrombopag, and the treatment was no response, with no adverse reactions.

Regulatory role of ceRNA network in B lymphocytes of patients with immune thrombocytopenia

OBJECTIVE

High-throughput sequencing was used to screen expressing differences of miRNA, lncRNA, and mRNA in CD19+ B peripheral blood samples of newly diagnosed immune thrombocytopenia (ITP) patients and healthy controls. The study aimed to explore the regulatory role of ceRNA network in the pathogenesis of dysfunctional CD19 + B lymphocytes of ITP patients.

METHODS

CD19+ B lymphocytes were isolated from peripheral blood samples of ITP patients and their healthy counterparts. High-throughput sequencing was used to screen for the expression of miRNA, lncRNA, and mRNA of ITP patients and healthy controls, which were analysed by the ceRNA network. Moreover, qPCR was used to verify the differential expression of miRNA, lncRNA, and mRNA in ITP patients and healthy controls. The correlation between differentially expressed miRNA, lncRNA, mRNA, and B lymphocyte subsets was also analysed.

RESULTS

The CD19+ B lymphocytes of 4 newly diagnosed ITP patients and 4 healthy controls were sequenced and analysed. There were 65 differentially expressed lncRNA and 149 mRNA forming a ceRNA network showed that 12 lncRNA and 136 differentially expressed mRNA were closely associated. Similarly, miR-144-3p, miR-374c-3p, and miR-451a were highly expressed in ITP patients, as confirmed by qPCR, which was consistent with the high-throughput sequence results. LOC102724852 and CCL20 were highly expressed in ITP patients, while LOC105378901, LOC112268311, ALAS2, and TBC1D3F were not as compared to healthy controls, which was consistent with the high-throughput sequence results. In addition, the expression of miR-374c-3p, LOC112268311, LOC105378901, and CXCL3 were correlated with the percentage of B lymphocyte subsets.

CONCLUSIONS

The ceRNA network of miRNA, lncRNA, and mRNA in peripheral CD19 + B lymphocytes plays an essential role in the pathogenesis of ITP.

Expression and prognostic value of C-reactive protein in adult immune thrombocytopenia (ITP) patients

The aim of this study was to investigate the effect of C-reactive protein (CRP) on the prognosis of adult patients with Immune thrombocytopenia purpura (ITP). A retrospective study of 628 adult ITP patients, as well as 100 healthy and 100 infected patients, attending the Affiliated Hospital of Xuzhou Medical University from January 2017 to June 2022 was performed. The ITP patients were grouped according to their CRP levels, and the differences in clinical characteristics of each group and the influencing factors of efficacy in newly diagnosed ITP patients were analyzed. CRP levels were significantly higher in the ITP and infected groups compared with healthy controls (P < 0.001), and platelet counts were significantly lower in the ITP group (P < 0.001). Between the CRP normal and elevated group, their age, white blood cell count, neutrophil count, lymphocyte count, red blood cell count, hemoglobin, platelet count, complement C3 and C4, PAIgG, bleeding score, proportion of severe ITP, and proportion of refractory ITP were significantly different (P < 0.05). Patients of severe ITP (P < 0.001), refractory ITP (P = 0.002), and with active bleeding (P < 0.001) had significantly higher CRP levels. Patients with no response after treatment had significantly higher CRP levels than those who achieved CR or R (P < 0.001). Platelet counts (r = - 0.261, P < 0.001) in newly diagnosed ITP patients and treatment outcomes (r = - 0.221, P < 0.001) were negatively correlated with CRP levels, and bleeding score was positively correlated with CRP levels (r = 0.207, P < 0.001). Treatment outcome was positively correlated with decrease in CRP levels (r = 0.313, P = 0.027). A multifactorial regression analysis of the influencing factors of treatment outcomes on newly diagnosed patients found that CRP was an independent risk factor of the prognosis (P = 0.011). In conclusion, CRP can help assess the severity and predict the prognosis of ITP patients.

Clinical and immunological characterisation of patients with common variable immunodeficiency related immune thrombocytopenia

Primary Immune thrombocytopenia (ITP) is an autoimmune disease. Secondary ITP occurs in patients with underlying diseases such as common variable immunodeficiency (CVID). CVID is one of the most common symptomatic primary immunodeficiencies in adults, characterised by infectious and non-infectious symptoms. Amongst CVID patients, ITP is the most frequent autoimmune manifestation. In this single-centre study, we performed a clinical and immunological characterisation of 20 patients with CVID-related ITP and 20 ITP patients without CVID to compare severity and remission rates. We found that patients with CVID-related ITP had a higher WHO Bleeding Scale at initial diagnosis yet showed higher remission rates and required less treatment. Patients with ITP needed up to seven therapy options and were often treated with second-line drug therapy, whilst only one CVID-related ITP patient required second-line drug therapy. Therefore, we show that the course of thrombocytopenia in patients with CVID-related ITP is milder. Furthermore, we show that soluble interleukin-2 receptor (sIL-2R, CD25) was higher in CVID-related ITP compared to ITP patients and could accurately classify patient cohorts with an Area Under the Receiver Operating Characteristic of 0.92. Whilst none of the ITP patients had a history of immunodeficiency, we found immunological abnormalities in 12 out of 18 patients. Therefore, we recommend screening ITP patients for CVID and other immunodeficiencies to detect immune abnormalities early, as we found patients with reduced immunoglobulin levels as well as severe lymphocytopenia in our ITP cohort.

Relationships of platelet glycoprotein specific antibody with therapeutic efficacy of short-term high-dose dexamethasone and bleeding score in the newly diagnosed adult patients with primary immune thrombocytopenia

Objectives: We aimed to investigate relationships of platelet glycoprotein (GP) specific antibody with therapeutic efficacy of high-dose dexamethasone (HD-DXM) and bleeding score in primary immune thrombocytopenia (ITP) adults. Methods: A retrospective study was carried out to analyze relationships of polymorphism of GP specific antibody with initial therapeutic efficacy of HD-DXM and bleeding score of newly diagnosed ITP adults between 1 June, 2016 and 31 January, 2020. Results: 59 patients were involved in the study, with 33 cases of responders and 26 cases of non-responders between June 2016 and January 2020. At admission, there were 31 (52.5%) GP antibody-positive patients. Initial therapy of HD-DXM was effective for 78.6% GP antibody-negative patients and 35.5% GP antibody-positive patients, with a better therapeutic efficacy in patients with anti-GP Ib/IX antibody or anti-GP IIb/IIIa antibody but not in those with anti-GP Ib/IX antibody plus anti-GP IIb/IIIa antibody. Notably, therapeutic efficacy is much worse for minority (Uyghur) patients compared with corresponding Han patients. Similarly, it was much lower in GP antibody-positive patients compared with corresponding negative ones at low and medium bleeding score, with no response in GP antibody-positive patients at high bleeding score. Furthermore, there was a moderate negative correlation between therapeutic efficacy and GP-specific antibody (p < 0.05), but no obvious linear relationship between clinical bleeding degree and GP-specific antibody (p > 0.05). Conclusion: Collectively, the newly diagnosed ITP adults with GP-specific antibody have a poor response to short-term HD-DXM, especially in minority (Uyghur) patients with GP-specific antibody in China.

The diagnostic accuracy of mean platelet volume in differentiating immune thrombocytopenic purpura from hypo-productive thrombocytopenia: A systematic review and meta-analysis

BACKGROUND

Thrombocytopenia is defined as a decreased number of platelets in the circulating blood as a result of hypo-proliferation in marrow or peripheral destruction of platelets. Several diagnostic methods have been proposed to discriminate the underline cause of thrombocytopenia. Recent studies showed that mean platelet volume (MPV) could be used for differential diagnosis of immune thrombocytopenic purpura (ITP). Thus, we aimed to investigate the diagnostic accuracy of MPV for differential diagnosis of ITP from hypo-productive thrombocytopenia.

METHODS

This study was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines (PRISMA). The study protocol was registered on PROSPERO with the reference number CRD42023447789. Relevant published studies that were published up to April 10, 2023, in peer-reviewed journals were searched on electronic different databases. The methodological quality of the included studies was appraised using the quality assessment of diagnostic accuracy studies 2 (QADAS-2) tool. The pooled weight mean difference (WMD) of MPV between the ITP group and hypo-productive group was analyzed using a random-effects model meta-analysis. Relevant data were extracted using a Microsoft Excel spreadsheet and analyzed using STATA 11.0 and Meta-disc 1.4 software. Publication bias was evaluated using Deek's funnel plot asymmetry test.

RESULTS

A total of 14 articles were included in this systematic review and meta-analysis. The comparison of MPV between groups revealed that the pooled mean value of MPV increased significantly in ITP patients compared to patients with hypo-productive thrombocytopenia (WMD = 2.03; 95% CI, 1.38-2.69). The pooled sensitivity and specificity of MPV in differentiating ITP from hypo-productive thrombocytopenia were 76.0% (95% CI: 71.0%, 80.0%) and 79.0% (95% CI: 75.0%, 83.0%), respectively. The summary positive likelihood ratio (PLR) and negative likelihood ratio (NLR)using the random effects model were 3.89 (95% CI: 2.49, 6.10) and 0.29 (95% CI: 0.18, 0.46), respectively.

CONCLUSION

MPV can be used to discriminate ITP from hypo-productive thrombocytopenia. It can possess large advantages as it is noninvasive, simple, quick, inexpensive, easy to perform, reliable, and routinely generated by automated cell counters.

Is Childhood Immune Thrombocytopenia Associated With Acquired Toxoplasmosis? An Unusual Case of Infection That Led to Acute ITP in a Greek Male Toddler and Implications for Guidelines

INTRODUCTION

Childhood immune thrombocytopenic purpura (ITP) is a heterogeneous immune-mediated process triggered by infections, vaccines, allergies and parasites. Currently, there is little evidence in the literature beyond case reports of an association with Toxoplasma gondii (T. gondii).

METHODS

The authors describe the unusual case of an earlier healthy 2.5-year-old Greek boy who developed acute ITP with a life-threatening platelet count a few days after a T. gondii infection. Evidence for the infection onset was found incidentally 3 months after the initial admission to the hospital and only after any other plausible cause of thrombocytopenia was excluded, according to diagnosis guidelines.

RESULTS

The boy underwent 3 intravenous immunoglobulin treatments within a trimester, a period during which his alarming platelets count levels led to housebound activities. A quite slow recovery was only ignited after the third treatment, which was administered in conjunction with a mild antibiotic medication for the T. gondii infection. Full recovery was obtained 9 months after the initial admission, although the boy's potential scored high in clinical prediction models for developing transient ITP.

CONCLUSION

There is a need for more research on ITPs with no obvious cause to investigate a causal association with toxoplasmosis. Currently, testing for diseases of greater rarity and of higher diagnostic cost than T. gondii is included in the ITP guidelines. Hence, routinely testing for toxoplasmosis when considering potential childhood ITP triggers and infection treatment complementary to treating the ITP might be the key to accelerating the healing process and improving the quality of life of otherwise confined children.

Clinical significance of antinuclear antibodies in primary immune thrombocytopenia

There are discrepancies across guidelines about whether the dosage of antinuclear antibodies (ANAs) is of use at the diagnosis of primary immune thrombocytopenia (ITP). This review describes the current knowledge about ANA prevalence in patients with primary ITP, and their potential usefulness as biomarkers for ITP evolution, response to treatments and increased risk of subsequent development of systemic lupus and thrombosis.

A proposal for new definition (s) and management approach to paediatric refractory ITP: Reflections from the Intercontinental ITP Study Group

Immune thrombocytopenia (ITP) in children is a relatively mild and self-limited disorder with the majority of children demonstrating normalization of platelet count by 12 months from diagnosis. Because of this, many children with ITP can be observed without the need for treatment. When needed, treatment with either intravenous immunoglobulin (IVIG) or corticosteroids is highly effective (>80% IVIG and >95% corticosteroids). For those children who require second-line therapies, response rates of >60% are seen with both the thrombopoietin-receptor agonists and rituximab. Despite this, some children will have 'refractory' ITP (rITP) with poor or transient responses to platelet-raising therapies. Here, we review the clinical features of rITP in children, outline proposed classifications and explore potential predictors for children with rITP.

Markers of refractory primary immune thrombocytopenia

Refractory immune thrombocytopenia (ITP) is a challenging disease that can be defined by refractoriness to second-line treatments. In this review, we list and comment available evidence about clinical and biological factors associated with refractoriness to splenectomy, thrombopoietin receptor agonists (TPO-RAs), rituximab and fostamatinib, as well as those associated with multirefractory ITP (active disease with failure of rituximab, TPO-RAs and splenectomy).

Refractory immune thrombocytopenia in adults: Towards a new definition

Immune thrombocytopenia (ITP) is an autoimmune haematological disorder characterized by immune-mediated thrombocytopenia and a variable risk of bleeding. Despite the availability of multiple treatment options, some patients are considered refractory since they do not achieve a platelet count response to multiple treatments and are at risk of bleeding. The term 'refractory' has been used to identify this patient group; however, with the advent of multiple lines of treatment, its meaning has become ambiguous. To address this issue, we reviewed previous definitions of refractory ITP, solicited the views of ITP experts and collected data from registries to inform a definition. Twenty ITP experts who attended the 7th Expert Meeting of the Intercontinental Cooperative ITP Study Group in September 2022 answered a web-based survey: 95% felt that there was a need for a new definition of refractory ITP for clinical and research purposes. The use of the term refractory, accompanied by a clear indication of the type and timing of failed treatments, was supported by 85% of respondents. Preliminary data on the frequency of refractory patients from the McMaster and Norwegian ITP Registries demonstrated that the proportion of adult ITP patients who had failed first-line therapy, rituximab, thrombopoietin receptor agonists, any immune suppressant medication and splenectomy ranged from 0.4% to 3.8%. We propose a definition of refractory ITP that could be evaluated in future studies.

Paediatric-onset Evans syndrome: Breaking away from refractory immune thrombocytopenia

Since its first description by Evans in 1951, this syndrome has been linked to chronic immune thrombocytopenia with the concurrent or delayed onset of autoimmune haemolytic anaemia or neutropenia. For decades, the evolution of Evans syndrome (ES) has carried a poor prognosis and often resulted in chronic steroid exposure, multiple immune suppressing medications directed against T or B lymphocytes, and splenectomy. This paper presents a new view of ES based on recent advances in genomics which begin to classify patients based on their underlying molecular variants in previously described primary immune disorders. This has opened up new avenues of targeted therapy or bone marrow transplant at rather than broad long-term immune suppression or splenectomy. Importantly, recent studies of the full lifespan of ES suggest that at least 80% of those paediatric patients will progress to various clinical or biological immunopathological manifestations with age despite the resolution of their cytopenias. Those patients merit long-term follow-up and monitoring in dedicated transition programs to improve outcome at the adult age.

Primary and secondary immune thrombocytopenia (ITP): Time for a rethink

There are not many publications that provide a holistic view of the management of primary and secondary ITP as a whole, reflecting the similarities and differences between the two. Given the lack of major clinical trials, we believe that comprehensive reviews are much needed to guide the diagnosis and treatment of ITP today. Therefore, our review addresses the contemporary diagnosis and treatment of ITP in adult patients. With respect to primary ITP we especially focus on establishing the management of ITP based on the different and successive lines of treatment. Life-threatening situations, "bridge therapy" to surgery or invasive procedures and refractory ITP are also comprehensively reviewed here. Secondary ITP is studied according to its pathogenesis by establishing three major differential groups: Immune Thrombocytopenia due to Central Defects, Immune Thrombocytopenia due to Blocked Differentiation and Immune Thrombocytopenia due to Defective Peripheral Immune Response. Here we provide an up-to-date snapshot of the current diagnosis and treatment of ITP, including a special interest in addressing rare causes of this disease in our daily clinical practice. The target population of this review is adult patients only and the target audience is medical professionals.

Long-term outcome in vaccine-induced immune thrombocytopenia and thrombosis

BACKGROUND

Rapid diagnosis and treatment has improved outcome of patients with vaccine-induced immune thrombocytopenia and thrombosis (VITT). However, after the acute episode, many questions on long-term management of VITT remained unanswered.

OBJECTIVES

To analyze, in patients with VITT, the long-term course of anti-platelet factor 4 (PF4) antibodies; clinical outcomes, including risk of recurrent thrombosis and/or thrombocytopenia; and the effects of new vaccinations.

METHODS

71 patients with serologically confirmed VITT in Germany were enrolled into a prospective longitudinal study and followed for a mean of 79 weeks from March 2021 to January 2023. The course of anti-PF4 antibodies was analyzed by consecutive anti-PF4/heparin immunoglobulin G enzyme-linked immunosorbent assay and PF4-enhanced platelet activation assay.

RESULTS

Platelet-activating anti-PF4 antibodies became undetectable in 62 of 71 patients (87.3%; 95% CI, 77.6%-93.2%). In 6 patients (8.5%), platelet-activating anti-PF4 antibodies persisted for >18 months. Five of 71 patients (7.0%) showed recurrent episodes of thrombocytopenia and/or thrombosis; in 4 of them (80.0%), alternative explanations beside VITT were present. After further COVID-19 vaccination with a messenger RNA vaccine, no reactivation of platelet-activating anti-PF4 antibodies or new thrombosis was observed. No adverse events occurred in our patients subsequently vaccinated against influenza, tick-borne encephalitis, varicella, tetanus, diphtheria, pertussis, and polio. No new thrombosis occurred in the 24 patients (33.8%) who developed symptomatic SARS-CoV-2 infection following recovery from acute VITT.

CONCLUSION

Once the acute episode of VITT has passed, patients appear to be at low risk for recurrent thrombosis and/or thrombocytopenia.

Serum from half of patients with immune thrombocytopenia trigger macrophage phagocytosis of platelets

Humoral antiplatelet factors, such as autoantibodies, are thought to primarily clear platelets by triggering macrophage phagocytosis in immune thrombocytopenia (ITP). However, there are few studies characterizing the capacity and mechanisms of humoral factor-triggered macrophage phagocytosis of platelets using specimens from patients with ITP. Here, we assessed sera from a cohort of 24 patients with ITP for the capacity to trigger macrophage phagocytosis of normal donor platelets and characterized the contribution of humoral factors to phagocytosis. Sera that produced a phagocytosis magnitude greater than a normal human serum mean + 2 standard deviations were considered phagocytosis-positive. Overall, 42% (8/19) of MHC I alloantibody-negative ITP sera were phagocytosis-positive. The indirect monoclonal antibody immobilization of platelet antigens assay was used to detect immunoglobulin G (IgG) autoantibodies to glycoproteins (GP)IIb/IIIa, GPIb/IX, and GPIa/IIa. Autoantibody-positive sera triggered a higher mean magnitude of phagocytosis than autoantibody-negative sera. Phagocytosis correlated inversely with platelet counts among autoantibody-positive patients but not among autoantibody-negative patients. Select phagocytosis-positive sera were separated into IgG-purified and -depleted fractions via protein G and reassessed for phagocytosis. Phagocytosis was largely retained in the purified IgG fractions. In addition, we assessed serum concentrations of C-reactive protein, serum amyloid P, and pentraxin 3 as potential phagocytosis modulators. Pentraxin 3 concentrations correlated inversely with platelet counts among patients positive for autoantibodies. Taken together, sera from approximately half of the patients with ITP studied triggered macrophage phagocytosis of platelets beyond a normal level. An important role for antiplatelet autoantibodies in phagocytosis is supported; a role for pentraxins such as pentraxin 3 may be suggested.