Clofarabine monotherapy in aggressive, relapsed and refractory Langerhans cell histiocytosis.

Over 50% of patients with systemic LCH are not cured with front-line therapies, and data to guide salvage options are limited. We describe 58 patients with LCH who were treated with clofarabine. Clofarabine monotherapy was active against LCH in this cohort, including heavily pretreated patients with a systemic objective response rate of 92.6%, higher in children (93.8%) than adults (83.3%). BRAFV600E+ variant allele frequency in peripheral blood is correlated with clinical responses. Prospective multicentre trials are warranted to determine optimal dosing, long-term efficacy, late toxicities, relative cost and patient-reported outcomes of clofarabine compared to alternative LCH salvage therapy strategies.

Real-world treatment patterns and outcomes in patients with primary hemophagocytic lymphohistiocytosis treated with emapalumab.

ABSTRACT: Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening, hyperinflammatory syndrome. Emapalumab, a fully human monoclonal antibody that neutralizes the proinflammatory cytokine interferon gamma, is approved in the United States to treat primary HLH (pHLH) in patients with refractory, recurrent, or progressive disease, or intolerance with conventional HLH treatments. REAL-HLH, a retrospective study, conducted across 33 US hospitals, evaluated real-world treatment patterns and outcomes in patients treated with ≥1 dose of emapalumab between 20 November 2018 and 31 October 2021. In total, 46 patients met the pHLH classification criteria. Median age at diagnosis was 1.0 year (range, 0.3-21.0). Emapalumab was initiated for treating refractory (19/46), recurrent (14/46), or progressive (7/46) pHLH. At initiation, 15 of 46 patients were in the intensive care unit, and 35 of 46 had received prior HLH-related therapies. Emapalumab treatment resulted in normalization of key laboratory parameters, including chemokine ligand 9 (24/33, 72.7%), ferritin (20/45, 44.4%), fibrinogen (37/38, 97.4%), platelets (39/46, 84.8%), and absolute neutrophil count (40/45, 88.9%). Forty-two (91.3%) patients were considered eligible for transplant. Pretransplant survival was 38 of 42 (90.5%). Thirty-one (73.8%) transplant-eligible patients proceeded to transplant, and 23 of 31 (74.2%) of those who received transplant were alive at the end of the follow-up period. Twelve-month survival probability from emapalumab initiation for the entire cohort (N = 46) was 73.1%. There were no discontinuations because of adverse events. In conclusion, results from the REAL-HLH study, which describes treatment patterns, effectiveness, and outcomes in patients with pHLH treated with emapalumab in real-world settings, are consistent with the emapalumab pivotal phase 2/3 pHLH trial.

Clinical and Treatment History of Patients with Partial DiGeorge Syndrome and Autoimmune Cytopenia at Multiple Centers.

BACKGROUND: Patients with partial DiGeorge syndrome (pDGS) can present with immune dysregulation, the most common being autoimmune cytopenia (AIC). There is a lack of consensus on the approach to type, combination, and timing of therapies for AIC in pDGS. Recognition of immune dysregulation early in pDGS clinical course may help individualize treatment and prevent adverse outcomes from chronic immune dysregulation. OBJECTIVES: Objectives of this study were to characterize the natural history, immune phenotype, and biomarkers in pDGS with AIC. METHODS: Data on clinical presentation, disease severity, immunological phenotype, treatment selection, and response for patients with pDGS with AIC were collected via retrospective chart review. Flow cytometric analysis was done to assess T and B cell subsets, including biomarkers of immune dysregulation. RESULTS: Twenty-nine patients with the diagnosis of pDGS and AIC were identified from 5 international institutions. Nineteen (62%) patients developed Evan's syndrome (ES) during their clinical course and twenty (69%) had antibody deficiency syndrome. These patients demonstrated expansion in T follicular helper cells, CD19hiCD21lo B cells, and double negative cells and reduction in CD4 naïve T cells and regulatory T cells. First-line treatment for 17/29 (59%) included corticosteroids and/or high-dose immunoglobulin replacement therapy. Other overlapping therapies included eltrombopag, rituximab, and T cell immunomodulators. CONCLUSIONS: AIC in pDGS is often refractory to conventional AIC treatment paradigms. Biomarkers may have utility for correlation with disease state and potentially even response to therapy. Immunomodulating therapies could be initiated early based on early immune phenotyping and biomarkers before the disease develops or significantly worsens.

Understanding the Spectrum of Immune Dysregulation Manifestations in Autoimmune Lymphoproliferative Syndrome and Autoimmune Lymphoproliferative Syndrome-like Disorders.

As a disorder of immune dysregulation, autoimmune lymphoproliferative syndrome (ALPS) stems from pathogenic variants in the first apoptosis signal-mediated apoptosis (Fas) and Fas-ligand pathway that result in elevations of CD3+ TCRαß+ CD4- CD8- T cells along with chronic lymphoproliferation, a heightened risk for malignancy, and importantly for the rheumatologist, increased risk of autoimmunity. While immune cytopenias are the most encountered autoimmune phenomena, there is increasing appreciation for ocular, musculoskeletal, pulmonary and renal inflammatory manifestations similar to more common rheumatology diseases. Additionally, ALPS-like conditions that share similar clinical features and opportunities for targeted therapy are increasingly recognized via genetic testing, highlighting the need for rheumatologists to be facile in the recognition and diagnosis of this spectrum of disorders. This review will focus on clinical and laboratory features of both ALPS and ALPS-like disorders with the intent to provide a framework for rheumatologists to understand the pathophysiologic drivers and discriminate between diagnoses.

Newborn tandem mass spectroscopy screening for adenosine deaminase deficiency.

BACKGROUND: Newborn screening (NBS) by means of T cell receptor excision circles (TREC) is now universal in the United States, Puerto Rico, and the Navajo Nation as a strategy to identify severe combined immunodeficiency (SCID) in newborns. Owing to the characteristics of adenosine deaminase (ADA) deficiency, a small but important number of cases can be missed by this screening. OBJECTIVE: To evaluate the results of the first year statewide NBS for ADA by means of dried blood spot NBS. METHODS: On October 7, 2019, the state of Michigan began screening newborn dried blood spots for ADA deficiency by means of the Neobase-2 tandem mass spectroscopy (TMS) kit. We report 1 known case of ADA deficiency in the 18 months before screening. We then reviewed the results of the first 2 years of TMS ADA screening in Michigan. RESULTS: There was 1 patient with ADA deficiency known to our centers in the 18 months before initiation of TMS ADA screening; this patient died of complications of their disease. In the first 2 years of TMS ADA NBS, 206,321 infants were screened, and 2 patients had positive ADA screen results. Both patients had ADA deficiency confirmed through biochemical and genetic testing. One patient identified also had a positive TREC screen and was confirmed to have ADA-SCID. CONCLUSION: In our first 2 years, TMS NBS for ADA deficiency identified 2 patients with ADA deficiency at negligible cost, including 1 patient who would not have been identified by TREC NBS. This report provides initial evidence of the value of specific NBS for ADA deficiency.

SOCS1 Haploinsufficiency Presenting as Severe Enthesitis, Bone Marrow Hypocellularity, and Refractory Thrombocytopenia in a Pediatric Patient with Subsequent Response to JAK Inhibition.

Haploinsufficiency of suppressor of cytokine signaling 1 (SOCS1) is a recently discovered autoinflammatory disorder with significant rheumatologic, immunologic, and hematologic manifestations. Here we report a case of SOCS1 haploinsufficiency in a 5-year-old child with profound arthralgias and immune-mediated thrombocytopenia unmasked by SARS-CoV-2 infection. Her clinical manifestations were accompanied by excessive B cell activity, eosinophilia, and elevated IgE levels. Uniquely, this is the first report of SOCS1 haploinsufficiency in the setting of a chromosomal deletion resulting in complete loss of a single SOCS1 gene with additional clinical findings of bone marrow hypocellularity and radiologic evidence of severe enthesitis. Immunologic profiling showed a prominent interferon signature in the patient's peripheral blood mononuclear cells, which were also hypersensitive to stimulation by type I and type II interferons. The patient showed excellent clinical and functional laboratory response to tofacitinib, a Janus kinase inhibitor that disrupts interferon signaling. Our case highlights the need to utilize a multidisciplinary diagnostic approach and consider a comprehensive genetic evaluation for inborn errors of immunity in patients with an atypical immune-mediated thrombocytopenia phenotype.

Case Report: Use of Obinutuzumab as an Alternative Monoclonal Anti-CD20 Antibody in a Patient With Refractory Immune Thrombocytopenia Complicated by Rituximab-Induced Serum Sickness and Anti-Rituximab Antibodies.

Management of refractory immune thrombocytopenia frequently involves rituximab, a chimeric anti-CD20 monoclonal antibody, to target B cells and induce remission in most patients. However, neutralizing antibodies to rituximab that nullify therapeutic response and may lead to serum sickness have been rarely reported. Here, we present a case of a young adult woman with Evans syndrome treated with rituximab, complicated by the development of serum sickness, acute respiratory distress syndrome, and platelet refractoriness presumed secondary to neutralizing antibodies to rituximab. She was successfully treated with the humanized anti-CD20 monoclonal antibody, obinutuzumab, with subsequent symptom resolution. Additionally, a review of 10 previously published cases of serum-sickness associated with the use of rituximab for idiopathic thrombocytopenic purpura (ITP) is summarized. This case highlights that recognition of more subtle or rare symptoms of rituximab-induced serum sickness is important to facilitate rapid intervention.

A Sherlock Approach to a Kindred With a Variable Immunohematologic Phenotype.

Given the ubiquity of leukopenia and sinopulmonary infections in childhood, differentiating patients with inborn errors of immunity (IEI) from otherwise healthy patients can be challenging. The diagnostic complexity is further exacerbated in disorders with wide phenotypic variability such as warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome. However, using a Sherlock approach with careful attention to details in the patient's medical history and physical examination coupled with a comprehensive family history can heighten the index of suspicion for underlying IEI. Subsequent iterative and deductive reasoning incorporating results from laboratory interrogation, response (or lack thereof) to standard therapy, and emergence of new symptoms can further aid in a timely diagnosis of IEI. Herein, we detail a WHIM syndrome kindred with marked phenotype variability, identified after the presentation of a child with intermittent neutropenia and sinopulmonary infections. The complexity of this kindred highlights the utility of an interspecialty, collaborative Sherlock approach to diagnosis, and care. In addition, the genetic underpinnings, diagnostic approaches, clinical features, supportive care options, and management of WHIM syndrome are reviewed.

Understanding neutropenia secondary to intrinsic or iatrogenic immune dysregulation.

As a key member of the innate and adaptive immune response, neutrophils provide insights into the hematopoietic and inflammatory manifestations of inborn errors of immunity (IEI) and the consequences of immunotherapy. The facile recognition of IEI presenting with neutropenia provides an avenue for hematologists to facilitate early diagnosis and expedite biologically rationale care. Moreover, enhancing the understanding of the molecular mechanisms driving neutropenia in IEI-decreased bone marrow reserves, diminished egress from the bone marrow, and decreased survival-offers an opportunity to further dissect the pathophysiology driving neutropenia secondary to iatrogenic immune dysregulation, eg, immune checkpoint inhibitors and chimeric antigen receptor T-cell therapy.

Diagnosis and therapeutic decision-making for the neutropenic patient.

Determining the cause of a low neutrophil count in a pediatric or adult patient is essential for the hematologist's clinical decision-making. Fundamental to this diagnostic process is establishing the presence or lack of a mature neutrophil storage pool, as absence places the patient at higher risk for infection and the need for supportive care measures. Many diagnostic tests, eg, a peripheral blood smear and bone marrow biopsy, remain important tools, but greater understanding of the diversity of neutropenic disorders has added new emphasis on evaluating for immune disorders and genetic testing. In this article, a structure is provided to assess patients based on the mechanism of neutropenia and to prioritize testing based on patient age and hypothesized pathophysiology. Common medical quandaries including fever management, need for growth factor support, risk of malignant transformation, and curative options in congenital neutropenia are reviewed to guide medical decision-making in neutropenic patients.

Histiocytic Neoplasms, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology.

Histiocytic neoplasms are rare hematologic disorders accounting for less than 1% of cancers of the soft tissue and lymph nodes. Clinical presentation and prognosis of these disorders can be highly variable, leading to challenges for diagnosis and optimal management of these patients. Treatment often consists of systemic therapy, and recent studies support use of targeted therapies for patients with these disorders. Observation ("watch and wait") may be sufficient for select patients with mild disease. These NCCN Guidelines for Histiocytic Neoplasms include recommendations for diagnosis and treatment of adults with the most common histiocytic disorders: Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease.

Impact of COVID-19 on Pediatric Immunocompromised Patients.

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Adjustments to pharmacologic therapies for hemophagocytic lymphohistiocytosis while on extracorporeal support.

Hemophagocytic lymphohistiocytosis (HLH) is an immune dysregulatory syndrome characterized by severe inflammation and end-organ damage. Due to significant organ dysfunction, patients often require extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT). In this report, we describe consideration for adjusting treatment in the context of extracorporeal organ support. We describe agents commonly used and dosing adjustments made in light of extracorporeal organ support. We report six cases that illustrate the feasibility of initiating standard HLH therapies in patients requiring these modalities.

Distinct genetic pathways define pre-malignant versus compensatory clonal hematopoiesis in Shwachman-Diamond syndrome.

To understand the mechanisms that mediate germline genetic leukemia predisposition, we studied the inherited ribosomopathy Shwachman-Diamond syndrome (SDS), a bone marrow failure disorder with high risk of myeloid malignancies at an early age. To define the mechanistic basis of clonal hematopoiesis in SDS, we investigate somatic mutations acquired by patients with SDS followed longitudinally. Here we report that multiple independent somatic hematopoietic clones arise early in life, most commonly harboring heterozygous mutations in EIF6 or TP53. We show that germline SBDS deficiency establishes a fitness constraint that drives selection of somatic clones via two distinct mechanisms with different clinical consequences. EIF6 inactivation mediates a compensatory pathway with limited leukemic potential by ameliorating the underlying SDS ribosome defect and enhancing clone fitness. TP53 mutations define a maladaptive pathway with enhanced leukemic potential by inactivating tumor suppressor checkpoints without correcting the ribosome defect. Subsequent development of leukemia was associated with acquisition of biallelic TP53 alterations. These results mechanistically link leukemia predisposition to germline genetic constraints on cellular fitness, and provide a rational framework for clinical surveillance strategies.

Quality of life and patient-reported outcomes in chronic severe neutropenia conditions.

Quality of life (QOL) and patient-reported outcomes (PROs) assessments in immunodeficiency patients, including those with chronic severe neutropenia conditions, are imperative to determining modifiable health-related features to optimize care. We present the largest study to date of QOL in those with chronic severe neutropenia conditions with further evaluation of patient provider satisfaction and patient-reported outcome measures. Subjects completed electronic surveys assessing QOL, PROs, and patient provider satisfaction. There is a significantly negative impact of a chronic severe neutropenia disorder on QOL, fatigue, physical function, cognitive function and pain in adult patients when compared to controls. Children with a chronic neutropenia condition had comparable QOL to controls, but reported fewer depressive symptoms, improved mobility, and stronger self-reported peer relationships. Adults had worse scores for QOL, depression and fatigue when compared to children. Adult and pediatric chronic severe neutropenia patients or their caregivers felt that their medical provider was compassionate, trustworthy, and accessible. However, less than 50% of adult patients agreed their clinician had excellent expertise in white blood cell disorders. Chronic neutropenia complexly affect QOL and PROs. An analysis of these parameters allows for targeted interventions to improve patient psychosocial, physical and neurocognitive health.

Line Associated Thrombosis in Pediatric Patients With NF-κB Pathway Variants.

Our report explores the complex role that nuclear factor-kappa B (NF-κB) plays in thrombosis formation, inflammation, and immunity; while additionally demonstrating that patients with NF-κB pathway pathogenic variants appear to carry a substantial thrombotic risk, particularly when secondary thrombotic risk factors are present. We propose that prophylactic anticoagulation should be strongly considered in such patients during high-risk situations and provide additional hematologic management strategies for those with NF-κB pathway alterations. We hope our work also calls to attention the potential need for a broader assessment of venous thromboembolism risk in patients with immune dysregulation to better delineate which patient populations may benefit from anticoagulation prophylaxis.