An update on pediatric ITP: differentiating primary ITP, IPD, and PID.

Immune thrombocytopenia (ITP) is the most common acquired thrombocytopenia in children and is caused by immune-mediated decreased platelet production and increased platelet destruction. In the absence of a diagnostic test, ITP must be differentiated from other thrombocytopenic disorders, including inherited platelet disorders. In addition, a diagnosis of secondary ITP due to a primary immune deficiency with immune dysregulation may not be apparent at diagnosis but can alter management and should be considered in an expanding number of clinical scenarios. The diagnostic evaluation of children with thrombocytopenia will vary based on the clinical history and laboratory features. Access to genotyping has broadened the ability to specify the etiology of thrombocytopenia, whereas increasing access to immunophenotyping, functional immunologic and platelet assays, and biochemical markers has allowed for more in-depth evaluation of patients. With this greater availability of testing, diagnostic algorithms in patients with thrombocytopenia have become complex. In this article, we highlight the diagnostic evaluation of thrombocytopenia in children with a focus on ITP, including consideration of underlying genetic and immune disorders, and use hypothetical patient cases to describe disease manifestations and strategies for treatment of pediatric ITP.

A case-control study of bleeding risk in children with 22q11.2 deletion syndrome undergoing cardiac surgery.

Previous research suggests that individuals with 22q11.2 deletion syndrome (DS) have an increased risk of bleeding following cardiac surgery. However, current guidelines for management of patients with 22q11.2DS do not provide specific recommendations for perioperative management. This study sought to identify specific risk factors for bleeding in this patient population. Examine the factors determining bleeding and transfusion requirements in patients with 22q11.2DS undergoing cardiac surgery. This was a single center review of patients who underwent cardiac surgery at the Children's Hospital of Philadelphia from 2000 to 2016. Data was extracted from the medical record. Frequency of bleeding events, laboratory values, and transfusion requirements were compared. We included 226 patients with 22q11.2DS and 506 controls. Bleeding events were identified in 13 patients with 22q11.2DS (5.8%) and 27 controls (5.3%). Platelet counts were lower among patients with 22q11.2DS than in control patients, but not statistically different comparing bleeding to not bleeding. Patients with 22q11.2DS received more transfusions (regardless of bleeding status). However, multivariate analysis showed only procedure type was associated with increased risk of bleeding (p = .012). The overall risk of bleeding when undergoing cardiac surgery is not different in patients with 22q11.2DS compared to non-deleted patients. Though platelet counts were lower in patients with 22q11.2DS, only procedure type was significantly associated with an increased risk of bleeding.

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.

Inherited bone marrow failure with macrothrombocytopenia due to germline tubulin beta class I (TUBB) variant.

Germline mutations in tubulin beta class I (TUBB), which encodes one of the ß-tubulin isoforms, were previously associated with neurological and cutaneous abnormalities. Here, we describe the first case of inherited bone marrow (BM) failure, including marked thrombocytopenia, morphological abnormalities, and cortical dysplasia, associated with a de novo p.D249V variant in TUBB. Mutant TUBB had abnormal cellular localisation in transfected cells. Following interferon/ribavirin therapy administered for transfusion-acquired hepatitis C, severe pancytopenia and BM aplasia ensued, which was unresponsive to immunosuppression. Acquired chromosome arm 6p loss of heterozygosity was identified, leading to somatic loss of the mutant TUBB allele.

Updated clinical practice recommendations for managing children with 22q11.2 deletion syndrome.

This review aimed to update the clinical practice guidelines for managing children and adolescents with 22q11.2 deletion syndrome (22q11.2DS). The 22q11.2 Society, the international scientific organization studying chromosome 22q11.2 differences and related conditions, recruited expert clinicians worldwide to revise the original 2011 pediatric clinical practice guidelines in a stepwise process: (1) a systematic literature search (1992-2021), (2) study selection and data extraction by clinical experts from 9 different countries, covering 24 subspecialties, and (3) creation of a draft consensus document based on the literature and expert opinion, which was further shaped by survey results from family support organizations regarding perceived needs. Of 2441 22q11.2DS-relevant publications initially identified, 2344 received full-text reviews, including 1545 meeting criteria for potential relevance to clinical care of children and adolescents. Informed by the available literature, recommendations were formulated. Given evidence base limitations, multidisciplinary recommendations represent consensus statements of good practice for this evolving field. These recommendations provide contemporary guidance for evaluation, surveillance, and management of the many 22q11.2DS-associated physical, cognitive, behavioral, and psychiatric morbidities while addressing important genetic counseling and psychosocial issues.

Platelet findings in 22q11.2 deletion syndrome correlate with disease manifestations but do not correlate with GPIb surface expression.

Prior studies have demonstrated that patients with chromosome 22q11.2 deletion syndrome (22q11.2DS) have lower platelet counts (PC) compared to non-deleted populations. They also have an increased mean platelet volume. The mechanism for this has been postulated to be haploinsufficiency of the GPIBB gene. We examined platelet parameters, deletion size and factors known to influence counts, including status of thyroid hormone and congenital heart disease (CHD), in a population of 825 patients with 22q11.2DS. We also measured surface expression of GPIB-IX complex by flow cytometry. The major determinant of PC was deletion status of GP1BB, regardless of surface expression or other factors. Patients with nested distal chromosome 22q11.2 deletions (those with GP1BB present) had higher PCs than those with proximal deletions where GP1BB is deleted. Patients with 22q11.2DS also demonstrated an accelerated PC decrease with age, occurring in childhood. These data demonstrate that genes within the proximal deletion segment drive PC differences in 22q11.2DS and suggest that PC reference ranges may need to be adjusted for age and deletion size in 22q11.2DS populations. Bleeding did not correlate with either platelet count or GPIb expression. Further studies into drivers of expression of GPIb and associations with severe thrombocytopenia and immune thrombocytopenia are needed to inform clinical care.

Sports participation in chronic immune thrombocytopenia: Safer than you thought?

BACKGROUND/OBJECTIVES: Pediatric patients with chronic immune thrombocytopenia (ITP) commonly have activity limitations placed to prevent injury without data guiding clinical decision-making. The objective of this study was to determine risk factors associated with injury in children with chronic ITP. DESIGN/METHODS: Retrospective single-center cohort study from January 1, 2008 to March 31, 2019 in subjects age 5-21 years with chronic ITP (platelet count < 100,000/µL for >1 year). RESULTS: One-hundred-two subjects were included, with a mean diagnosis age of 9.3 ± 4.6 years. Mean follow-up 3.8 ± 2.3 years; 61% (62) of subjects were female; 60% (61) participated in organized sports, mean 2 ± 1 sports/subject; 8.8% (9) received ITP therapy for sports participation. Common sports: basketball (28%) and soccer (28%). There were 31 injuries in 26 subjects, and 68% (21) occurred while at play. Most common injuries: 68% (21/31) soft tissue and 23% (7/31) head trauma. Fifteen (48%) injuries were severe enough for medical evaluation at the time of injury. Only one patient received acute ITP treatment for their injury. Injury was associated with participation in high-risk sports (p < .001), male sex (p = .007), and participation in multiple organized sports (p = .008). CONCLUSION: In this study of 102 pediatric subjects with chronic ITP, injury was mild and infrequent predominantly occurring while at play. The majority participated in organized sports safely. Risk of injury was associated with high-risk sport participation (p < .001). Only one injury necessitated ITP treatment, suggesting that participation in most sports is likely safe in children with chronic ITP.

Distinct immune trajectories in patients with chromosome 22q11.2 deletion syndrome and immune-mediated diseases.

BACKGROUND: Identification of biomarkers associated with immune-mediated diseases in 22q11.2 deletion syndrome is an evolving field. OBJECTIVES: We sought to use a carefully phenotyped cohort to study immune parameters associated with autoimmunity and atopy in 22q11.2 deletion syndrome to define biomarkers associated with immune-mediated disease in this syndrome. METHODS: Chart review validated autoimmune disease and atopic condition diagnoses. Laboratory data were extracted for each subcohort and plotted according to age. A random-effects model was used to define statistical significance. RESULTS: CD19, CD4, and CD4/45RA lymphocyte populations were not different from the general cohort for patients with atopic conditions. CD4/45RA T cells were significantly lower in the subjects with immune thrombocytopenia compared with the general cohort, and CD4 T-cell counts were lower in patients with autoimmune thyroid disease. CONCLUSIONS: The mechanisms of autoimmunity in cytopenias may be distinct from those of solid-organ autoimmunity in 22q11.2 deletion syndrome. This study identifies potential biomarkers for risk stratification among commonly obtained laboratory studies.

Hematologic abnormalities in Aicardi Goutières Syndrome.

BACKGROUND: Because of the broad clinical spectrum, heritable autoinflammatory diseases present a management and therapeutic challenge. The most common genetic interferonopathy, Aicardi Goutières Syndrome (AGS), is associated with early onset neurologic disability and systemic inflammation. The chronic inflammation of AGS is the result of dysregulation of interferon (IFN) expression by one of nine genes within converging pathways. While each AGS subtype shares common features, distinct patterns of severity and potential for systemic complications amongst the genotypes are emerging. Multilineage cytopenias are a potentially serious, but poorly understood, complication of AGS. As immunomodulatory treatment options are developed, it is important to characterize the role of the disease versus treatment in hematologic abnormalities. This will allow for better understanding and management of cytopenia. METHODS: In total, 142 individuals with molecularly-confirmed AGS were included. Information on genotype, demographics, and all available hematologic laboratory values were collected from existing medical records. As part of a clinical trial, a subset of this cohort (n = 52) were treated with a janus kinase inhibitor (baricitinib), and both pre- and post-treatment values were included. Abnormal values were graded based on Common Terminology Criteria for Adverse Events (CTCAE v5.0), supplemented with grading definitions for thrombocytosis, and were compared across genotypes and baricitinib exposure. RESULTS: In total, 11,184 laboratory values were collected over a median of 2.54 years per subject (range 0-22.68 years). To reduce bias from repeated sampling within a limited timeframe, laboratory results were restricted to the most abnormal value within a month (n = 8485). The most common abnormalities were anemia (noted in 24% of subjects prior to baricitinib exposure), thrombocytopenia (9%), and neutropenia (30%). Neutropenia was most common in the SAMHD1 cohort and increased with baricitinib exposure (38/69 measurements on baricitinib versus 14/121 while not on baricitinib). Having an abnormality prior to treatment was associated with having an abnormality on treatment for neutropenia and thrombocytopenia. CONCLUSION: By collecting available laboratory data throughout the lifespan, we were able to identify novel patterns of hematologic abnormalities in AGS. We found that AGS results in multilineage cytopenias not limited to the neonatal period. Neutropenia, anemia, and thrombocytopenia were common. Moderate-severe graded events of neutropenia, anemia, and leukopenia were more common on baricitinib, but rarely of clinical consequence. Based on these results, we would recommend careful monitoring of hematologic parameters of children affected by AGS throughout the lifespan, especially while on therapy, and consideration of AGS as a potential differential diagnosis in children with neurologic impairment of unclear etiology with hematologic abnormalities. Trial registration ClinicalTrials.gov Identifier: NCT01724580 ClinicalTrials.gov Identifier: NCT03921554.

Hemolysis After Medication Exposure in Pediatric Patients With G6PD Deficiency.

Hemolysis in glucose-6-phosphate dehydrogenase (G6PD) deficiency varies by mutation status and the oxidative stressor. Although classified by percent of enzymatic deficiency, variability in normal G6PD values clouds assessment of hemolysis risk by level. This was a retrospective, single institution, cohort study assessing risk of postexposure medication-induced hemolysis in G6PD deficient patients. Exposures occurred in 87 of 1415 deficient patients. Only 2 of 87 medication-exposed patients had hemolytic episodes and both had very low enzymatic activity. No hemolytic events occurred with G6PD levels >7 units/g hemoglobin. Correlation of levels with mutation may improve predictive capacity for hemolysis in G6PD deficiency.

Thromboelastography Changes of Whole Blood Compared to Blood Component Transfusion in Infant Craniosynostosis Surgery.

ABSTRACT: Surgical treatment of craniosynostosis with cranial vault reconstruction in infants is associated with significant blood loss. The optimal blood management approach is an area of active investigation. Thromboelastography (TEG) was used to examine changes in coagulation after surgical blood loss that was managed by transfusion with either whole blood or blood components. Transfusion type was determined by availability of whole blood from the blood bank.This retrospective study examined differences in posttransfusion TEG maximum amplitude (MA), a measure of the maximum clot strength, for patients transfused with whole blood or blood components. We included all patients less than 24 months old who underwent cranial vault remodeling, received intraoperative transfusions with whole blood or blood components, and had baseline and posttransfusion TEG measured. Whole blood was requested for all patients and was preferentially used when it was available from the American Red Cross.Of 48 eligible patients, 30 received whole blood and 18 received blood components. All patients received an intraoperative antifibrinolytic agent. The posttransfusion MA in the whole blood group was 61.8 mm (IQR 59.1, 64.1) compared to 57.9 mm (IQR 50.5, 60.9) in the blood components group (P = 0.010). There was a greater posttransfusion decrease in MA for patients transfused with blood components (median decrease of 7.7 mm [IQR -3.4, 6.3]) compared with whole blood (median decrease of 2.1 mm [IQR -9.6, 7.5] P < 0.001).Transfusion with blood components was associated with a greater decrease in MA that was likely related to decreased postoperative fibrinogen in this group. Patients who received whole blood had higher postoperative fibrinogen levels.

Diagnostic Challenges in Pediatric Hemophagocytic Lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of severe immune dysregulation that encompasses a broad range of underlying genetic diseases and infectious triggers. Monogenic conditions, autoimmune diseases, and infections can all drive the phenotype of HLH and associated immune hyperactivation with hypercytokinemia. A diagnosis of HLH usually requires a combination of clinical and laboratory findings; there is no single sensitive and specific diagnostic test, which often leads to "diagnostic dilemmas" and delays in treatment initiation. Ferritin levels, one of the most commonly used screening tests, were collected across a large tertiary care pediatric hospital to identify the positive predictive value for HLH. Herein, we present several cases that illustrate the clinical challenges of confirming an HLH diagnosis. Additionally, we report on the utility of establishing a formal multi-disciplinary group to aid the prompt diagnosis and treatment of patients presenting with HLH-like pathophysiologies.

Refractory autoimmune cytopenias in pediatric Evans syndrome with underlying systemic immune dysregulation.

Evans syndrome is a rare but challenging disorder in children; and despite rapidly growing evidence for targetable systemic immune dysregulation driving these "idiopathic" autoimmune cytopenias, precision diagnosis and management remains sub-optimal among these patients. We analyzed retrospective clinical data for 60 pediatric ES patients followed at 3 large tertiary referral centers in the United States over a recent 6-year period and found that definable underlying systemic immune dysregulation was identified in only 42% of these patients throughout the course of clinical care. Median time from ES diagnosis to identification of the underlying systemic immune dysregulation disorder was 1.3 years (<1 month for rheumatologic disease, 2.3 years for CVID, 3.4 years for ALPS, and 7.4 years for monogenic disorders of immune regulation). Notably, a significantly higher percentage of patients in whom a definitive immune dysregulation disorder was ultimately identified required ≥3 cytopenia-directed therapies (92%) and also second- and third-line immunomodulatory agents (84%), vs those in whom no unifying immune dysregulation was diagnosed (65%, and 35%, respectively)-indicating that autoimmune cytopenias as a manifestation of systemic immune dysregulation are more treatment-refractory and severe. These data underline the importance of identifying the underlying systemic immune dysregulation and providing targeted therapy in pediatric ES.

Quality of life is an important indication for second-line treatment in children with immune thrombocytopenia.

BACKGROUND: The decision to initiate second-line treatment in children with immune thrombocytopenia (ITP) is complex and involves many different factors. METHODS: In this prospective, observational, longitudinal cohort study of 120 children from 21 centers, the factors contributing to the decision to start second-line treatments for ITP were captured. At study entry, clinicians were given a curated list of 12 potential reasons the patient required a second-line treatment. Clinicians selected all that applied and ranked the top three reasons. RESULTS: Quality of life (QOL) was the most frequently cited reason for starting a second-line therapy. Clinicians chose it as a reason to treat in 88/120 (73%) patients, as among the top three reasons in 68/120 (57%), and as the top reason in 32/120 (27%). Additional factors ranked as the top reason to start second-line treatment included severity of bleeding (22/120, 18%), frequency of bleeding (19/120, 16%), and severity of thrombocytopenia (18/120, 15%). Patients for whom QOL (p = .006) or sports participation (p = .02) were ranked reasons were more likely to have chronic ITP, whereas those for whom severity (p = .003) or frequency (p = .005) of bleeding were ranked reasons were more likely to have newly diagnosed or persistent ITP. Parental anxiety, though rarely the primary impetus for treatment, was frequently cited (70/120, 58%) as a contributing factor. CONCLUSION: Perceived QOL is the most frequently selected reason pediatric patients start second-line therapies for ITP. It is critical that studies of treatments for childhood ITP include assessments of their effects on QOL.

Thrombocytosis in an infant with a TRPV4 mutation: a case report.

Mutations in the calcium channel gene Transient Receptor Potential cation channel subfamily V member 4 (TRPV4) cause autosomal dominant skeletal dysplasia, with phenotypes ranging from mild to perinatal lethality. A recent report detailed enhanced proplatelet formation and increased murine platelet count in the context of TRPV4 activation. No prior reports have described platelet count abnormalities in human TRPV4 disease. Here, we report a case of prolonged thrombocytosis in the context of TRPV4-associated metatropic dysplasia that was lethal in the infantile period.

Updates in diagnosis of the inherited platelet disorders.

PURPOSE OF REVIEW: To provide a comprehensive update on the current available methodologies and techniques for diagnosis of inherited platelet disorders (IPD). RECENT FINDINGS: The contributions of many groups have resulted in the significant progress in the molecular diagnosis of IPD including the identification of many genes responsible for the various phenotypes. The widespread use and availability of next-generation sequencing has brought to the forefront ethical challenges associated with nontargeted sequencing as well as provided us with novel variants to functionally validate. These requirements have driven the development of novel tools for functional assessment of platelets, although none of the novel techniques beyond sequencing have yet taken clinical hold. SUMMARY: Much work is ongoing on functional and molecular assessment of platelet disorders and the incorporation of combined assessments is likely to yield the highest diagnostic results.

Next-generation sequencing for the diagnosis of MYH9-RD: Predicting pathogenic variants.

The heterogeneous manifestations of MYH9-related disorder (MYH9-RD), characterized by macrothrombocytopenia, Döhle-like inclusion bodies in leukocytes, bleeding of variable severity with, in some cases, ear, eye, kidney, and liver involvement, make the diagnosis for these patients still challenging in clinical practice. We collected phenotypic data and analyzed the genetic variants in more than 3,000 patients with a bleeding or platelet disorder. Patients were enrolled in the BRIDGE-BPD and ThromboGenomics Projects and their samples processed by high throughput sequencing (HTS). We identified 50 patients with a rare variant in MYH9. All patients had macrothrombocytes and all except two had thrombocytopenia. Some degree of bleeding diathesis was reported in 41 of the 50 patients. Eleven patients presented hearing impairment, three renal failure and two elevated liver enzymes. Among the 28 rare variants identified in MYH9, 12 were novel. HTS was instrumental in diagnosing 23 patients (46%). Our results confirm the clinical heterogeneity of MYH9-RD and show that, in the presence of an unclassified platelet disorder with macrothrombocytes, MYH9-RD should always be considered. A HTS-based strategy is a reliable method to reach a conclusive diagnosis of MYH9-RD in clinical practice.

Fatigue in children and adolescents with immune thrombocytopenia.

Immune thrombocytopenia (ITP), an acquired autoimmune disorder of low platelets and risk of bleeding, has a substantial impact on health-related quality of life (HRQoL). Patients with ITP often report significant fatigue, although the pathophysiology of this is poorly understood. In this observational cohort of 120 children receiving second-line therapies for ITP, we assessed reports of fatigue using the Hockenberry Fatigue Scale. Children and adolescents with ITP reported a similarly high level of fatigue with 54% (29/54) of children and 62% (26/42) of adolescents reporting moderate-to-severe fatigue. There was no correlation between fatigue and age or gender. Adolescents with newly diagnosed and persistent ITP had higher mean fatigue scores than those with chronic ITP (P = 0·03). Fatigue significantly improved in children and adolescents by 1 month after starting second-line treatments, and this improvement continued to be present at 12 months after starting treatment. Fatigue scores at all time-points correlated with general HRQoL using the Kids ITP Tool, but did not correlate with bleeding symptoms, platelet count, or platelet response to treatment. Fatigue is common in children and adolescents with ITP and may benefit from ITP-directed treatment even in the absence of bleeding symptoms.

Glanzmann thrombasthenia: genetic basis and clinical correlates.

Glanzmann thrombasthenia (GT) is an autosomal recessive disorder of platelet aggregation caused by quantitative or qualitative defects in integrins αIIb and ß3. These integrins are encoded by the ITGA2B and ITGB3 genes and form platelet glycoprotein (GP)IIb/IIIa, which acts as the principal platelet receptor for fibrinogen. Although there is variability in the clinical phenotype, most patients present with severe mucocutaneous bleeding at an early age. A classic pattern of abnormal platelet aggregation, platelet glycoprotein expression and molecular studies confirm the diagnosis. Management of bleeding is based on a combination of hemostatic agents including recombinant activated factor VII with or without platelet transfusions and antifibrinolytic agents. Refractory bleeding and platelet alloimmunization are common complications. In addition, pregnant patients pose unique management challenges. This review highlights clinical and molecular aspects in the approach to patients with GT, with particular emphasis on the significance of multidisciplinary care.

Genetic variants in toll-like receptor 4 are associated with lack of steroid-responsiveness in pediatric ITP patients.

Although the most common front-line therapies for immune thrombocytopenia (ITP) have been in use for decades, it is still not possible to predict an individual patient's clinical course and response to therapy. Patients are managed with a trial-and-error approach and often suffer side effects of therapies which could have been avoided if response prediction were possible. Corticosteroids are the most frequently used upfront therapy for adults and children with ITP. Our group performed whole exome sequencing on a cohort of pediatric ITP patients, and identified two missense single nucleotide variants (SNV) in Toll-like receptor 4 (TLR4). These coding variants in TLR4 had an increased frequency in Caucasian patients with poor response to upfront steroid therapy. Both TLR4 (D299G; rs4986790) and TLR4 (T399I; rs4986791) had a minor allele frequency (MAF) of 20.7% in those patients unresponsive to steroids, but were present at lower allele frequencies of 2.3% and 3.4% in responders respectively (P < .001). These findings were consistent with the trend identified in an independent cohort of pediatric ITP patients treated with corticosteroids who underwent direct genotyping for both SNVs. This study identified two candidate genetic variants in two unique cohorts of ITP patients which may contribute to steroid response and have prognostic implications for treatment response in ITP.