JMML and RALD (Ras-associated autoimmune leukoproliferative disorder): common genetic etiology yet clinically distinct entities

Somatic mutations in autoinflammatory and autoimmune disease

Somatic mutations (also known as acquired mutations) are emerging as common, age-related processes that occur in all cells throughout the body. Somatic mutations are canonically linked to malignant processes but over the past decade have been increasingly causally connected to benign diseases including rheumatic conditions. Here we outline the contribution of somatic mutations to complex and monogenic immunological diseases with a detailed review of unique aspects associated with such causes. Somatic mutations can cause early- or late-onset rheumatic monogenic diseases but also contribute to the pathogenesis of complex inflammatory and immune-mediated diseases, affect disease progression and define new clinical subtypes. Although even variants with a low variant allele fraction can be pathogenic, clonal dynamics could lead to changes over time in the proportion of mutant cells, with possible phenotypic consequences for the individual. Thus, somatic mutagenesis and clonal expansion have relevant implications in genetic testing and counselling. On the basis of both increased recognition of somatic diseases in clinical practice and improved technical and bioinformatic processes, we hypothesize that there will be an ever-expanding list of somatic mutations in various genes leading to inflammatory conditions, particularly in late-onset disease.

A predictive classifier of poor prognosis in transplanted patients with juvenile myelomonocytic leukemia: a study on behalf of the Société Francophone de Greffe de Moelle et de Thérapie Cellulaire

Juvenile myelomonocytic leukemia (JMML) is an aggressive pediatric myeloproliferative neoplasm requiring hematopoietic stem cell transplantation (HSCT) in most cases. We retrospectively analyzed 119 JMML patients who underwent first allogeneic HSCT between 2002 and 2021. The majority (97%) carried a RAS-pathway mutation, and 62% exhibited karyotypic alterations or additional mutations in SETBP1, ASXL1, JAK3 and/or the RAS pathway. Relapse was the primary cause of death, with a 5-year cumulative incidence of 24.6% (95% CI: 17.1-32.9). Toxic deaths occurred in 12 patients, resulting in treatment-related mortality (TRM) of 9.0% (95% CI: 4.6-15.3). The 5-year overall (OS) and event-free survival were 73.6% (95% CI: 65.7-82.4) and 66.4% (95% CI: 58.2-75.8), respectively. Four independent adverse prognostic factors for OS were identified: age at diagnosis >2 years, time from diagnosis to HSCT ≥6 months, monocyte count at diagnosis >7.2x109/L, and the presence of additional genetic alterations. Based on these factors, we proposed a predictive classifier. Patients with 3 or more predictors (21% of the cohort) had a 5-year OS of 34.2%, whereas those with none (7%) had a 5-year OS of 100%. Our study demonstrates improved transplant outcomes compared to prior published data, which can be attributed to the synergistic impacts of a low TRM and a reduced, yet still substantial, relapse incidence. By integrating genetic information with clinical and hematologic features, we have devised a predictive classifier. This classifier effectively identifies a subgroup of patients who are at a heightened risk of unfavorable post-transplant outcomes who would benefit from novel therapeutic agents and post-transplant strategies.

Ras-associated autoimmune lymphoproliferative disorder

Distinguishing RALD from JMML can be difficult. This review discusses the clinical features, genetic aetiology and the treatments that are common and distinct between the two diagnoses.

Monoallelic KRAS (G13C) mutation triggers dysregulated expansion in induced pluripotent stem cell-derived hematopoietic progenitor cells

BACKGROUND

Although oncogenic RAS mutants are thought to exert mutagenic effects upon blood cells, it remains uncertain how a single oncogenic RAS impacts non-transformed multipotent hematopoietic stem or progenitor cells (HPCs). Such potential pre-malignant status may characterize HPCs in patients with RAS-associated autoimmune lymphoproliferative syndrome-like disease (RALD). This study sought to elucidate the biological and molecular alterations in human HPCs carrying monoallelic mutant KRAS (G13C) with no other oncogene mutations.

METHODS

We utilized induced pluripotent stem cells (iPSCs) derived from two unrelated RALD patients. Isogenic HPC pairs harboring either wild-type KRAS or monoallelic KRAS (G13C) alone obtained following differentiation enabled reliable comparative analyses. The compound screening was conducted with an established platform using KRAS (G13C) iPSCs and differentiated HPCs.

RESULTS

Cell culture assays revealed that monoallelic KRAS (G13C) impacted both myeloid differentiation and expansion characteristics of iPSC-derived HPCs. Comprehensive RNA-sequencing analysis depicted close clustering of HPC samples within the isogenic group, warranting that comparative studies should be performed within the same genetic background. When compared with no stimulation, iPSC-derived KRAS (G13C)-HPCs showed marked similarity with the wild-type isogenic control in transcriptomic profiles. After stimulation with cytokines, however, KRAS (G13C)-HPCs exhibited obvious aberrant cell-cycle and apoptosis responses, compatible with "dysregulated expansion," demonstrated by molecular and biological assessment. Increased BCL-xL expression was identified amongst other molecular changes unique to mutant HPCs. With screening platforms established for therapeutic intervention, we observed selective activity against KRAS (G13C)-HPC expansion in several candidate compounds, most notably in a MEK- and a BCL-2/BCL-xL-inhibitor. These two compounds demonstrated selective inhibitory effects on KRAS (G13C)-HPCs even with primary patient samples when combined.

CONCLUSIONS

Our findings indicate that a monoallelic oncogenic KRAS can confer dysregulated expansion characteristics to non-transformed HPCs, which may constitute a pathological condition in RALD hematopoiesis. The use of iPSC-based screening platforms will lead to discovering treatments that enable selective inhibition of RAS-mutated HPC clones.

Clonal hematopoiesis in children with predisposing conditions

Clonal hematopoiesis in children and young adults differs from that occuring in the older adult population. A variety of stressors drive this phenomenon, sometimes independent of age-related processes. For the purposes of this review, we adopt the term clonal hematopoiesis in predisposed individuals (CHIPI) to differentiate it from classical, age-related clonal hematopoiesis of indeterminate potential (CHIP). Stress-induced CHIPI selection can be extrinsic, such as following immunologic, infectious, pharmacologic, or genotoxic exposures, or intrinsic, involving germline predisposition from inherited bone marrow failure syndromes. In these conditions, clonal advantage relates to adaptations allowing improved cell fitness despite intrinsic defects affecting proliferation and differentiation. In certain contexts, CHIPI can improve competitive fitness by compensating for germline defects; however, the downstream effects of clonal expansion are often unpredictable - they may either counteract the underlying pathology or worsen disease outcomes. A more complete understanding of how CHIPI arises in young people can lead to the definition of preleukemic states and strategies to assess risk, surveillance, and prevention to leukemic transformation. Our review summarizes current research on stress-induced clonal dynamics in individuals with germline predisposition syndromes.

Phenotypic profiling of CD34+ cells by advanced flow cytometry improves diagnosis of juvenile myelomonocytic leukemia

Diagnostic criteria for juvenile myelomonocytic leukemia (JMML) are currently well defined, however in some patients diagnosis still remains a challenge. Flow cytometry is a well established tool for diagnosis and follow-up of hematological malignancies, nevertheless it is not routinely used for JMML diagnosis. Herewith, we characterized the CD34+ hematopoietic precursor cells collected from 31 children with JMML using a combination of standardized EuroFlow antibody panels to assess the ability to discriminate JMML cells from normal/reactive bone marrow cell as controls (n=29) or from cells of children with other hematological diseases mimicking JMML (n=9). CD34+ precursors in JMML showed markedly reduced B-cell and erythroid-committed precursors compared to controls, whereas monocytic and CD7+ lymphoid precursors were significantly expanded. Moreover, aberrant immunophenotypes were consistently present in CD34+ precursors in JMML, while they were virtually absent in controls. Multivariate logistic regression analysis showed that combined assessment of the number of CD34+CD7+ lymphoid precursors and CD34+ aberrant precursors or erythroid precursors had a great potential in discriminating JMMLs versus controls. Importantly our scoring model allowed highly efficient discrimination of truly JMML versus patients with JMML-like diseases. In conclusion, we show for the first time that CD34+ precursors from JMML patients display a unique immunophenotypic profile which might contribute to a fast and accurate diagnosis of JMML worldwide by applying an easy to standardize single eight-color antibody combination.

Clonal Hematopoiesis, Inflammation, and Hematologic Malignancy

Somatic or acquired mutations are postzygotic genetic variations that can occur within any tissue. These mutations accumulate during aging and have classically been linked to malignant processes. Tremendous advancements over the past years have led to a deeper understanding of the role of somatic mutations in benign and malignant age-related diseases. Here, we review the somatic mutations that accumulate in the blood and their connection to disease states, with a particular focus on inflammatory diseases and myelodysplastic syndrome. We include a definition of clonal hematopoiesis (CH) and an overview of the origins and implications of these mutations. In addition, we emphasize somatic disorders with overlapping inflammation and hematologic disease beyond CH, including paroxysmal nocturnal hemoglobinuria and aplastic anemia, focusing on VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome. Finally, we provide a practical view of the implications of somatic mutations in clinical hematology, pathology, and beyond.

Diagnostic work-up of hematological malignancies with underlying germline predisposition disorders (GPD)

Hematological malignancies with underlying germline predisposition disorders have been recognized by the World Health Organization 5th edition and International Consensus Classification (ICC) classification systems. The list of genes and the associated phenotypes are expanding and involve both pediatric and adult populations. While the clinical presentation and underlying molecular pathogenesis are relatively well described, the knowledge regarding the bone marrow morphologic features, the landscape of somatic aberrations associated with progression to hematological malignancies is limited. These pose challenges in the diagnosis of low-grade myelodysplastic syndrome (MDS) to hematopathologists which carries direct implication for various aspects of clinical management of the patient, donor selection for transplantation, and family members. Here in, we provide a focused review on the diagnostic work-up of hematological malignancies with underlying germline predisposition disorders with emphasis on the spectrum of hematological malignancies associated with each entity, and characteristic bone marrow morphologic, somatic cytogenetic and molecular alterations at the time of diagnosis of hematological malignancies. We also review the key clinical, morphologic, and molecular features, that should initiate screening for these entities.

A young woman with persistent sore throat, Epstein-Barr virus, lymphadenopathy, and aberrant CD4 + CD7- T-cells

A young woman with persistent EBV viremia and lymphocytosis had an abnormal CD4- T cell population with aberrant loss of CD7. She had a diagnosis of chronic active EBV (CAEBV), a lymphoproliferative disorder for which she ultimately required allogeneic hematopoietic stem cell transplantation.

The International Consensus Classification (ICC) of hematologic neoplasms with germline predisposition, pediatric myelodysplastic syndrome, and juvenile myelomonocytic leukemia

Updating the classification of hematologic neoplasia with germline predisposition, pediatric myelodysplastic syndrome (MDS), and juvenile myelomonocytic leukemia (JMML) is critical for diagnosis, therapy, research, and clinical trials. Advances in next-generation sequencing technology have led to the identification of an expanding group of genes that predispose to the development of hematolymphoid neoplasia when mutated in germline configuration and inherited. This review encompasses recent advances in the classification of myeloid and lymphoblastic neoplasia with germline predisposition summarizing important genetic and phenotypic information, relevant laboratory testing, and pathologic bone marrow features. Genes are organized into three major categories including (1) those that are not associated with constitutional disorder and include CEBPA, DDX41, and TP53; (2) those associated with thrombocytopenia or platelet dysfunction including RUNX1, ANKRD26, and ETV6; and (3) those associated with constitutional disorders affecting multiple organ systems including GATA2, SAMD9, and SAMD9L, inherited genetic mutations associated with classic bone marrow failure syndromes and JMML, and Down syndrome. A provisional category of germline predisposition genes is created to recognize genes with growing evidence that may be formally included in future revised classifications as substantial supporting data emerges. We also detail advances in the classification of pediatric myelodysplastic syndrome (MDS), expanding the definition of refractory cytopenia of childhood (RCC) to include early manifestation of MDS in patients with germline predisposition. Finally, updates in the classification of juvenile myelomonocytic leukemia are presented which genetically define JMML as a myeloproliferative/myelodysplastic disease harboring canonical RAS pathway mutations. Diseases with features overlapping with JMML that do not carry RAS pathway mutations are classified as JMML-like. The review is based on the International Consensus Classification (ICC) of Myeloid and Lymphoid Neoplasms as reported by Arber et al. (Blood 140(11):1200-1228, 2022).

Mosaic RASopathies: A review of disorders caused by somatic pathogenic variants in the genes of the RAS/MAPK pathway

Mosaic RASopathies are a heterogeneous group of diseases characterized by the presence at birth or early onset of congenital anomalies, cutaneous and vascular anomalies, segmental overgrowth, and increased cancer risk. They are caused by somatic pathogenic variants of the genes belonging the RAt Sarcoma Mitogen-activated protein kinase (RAS/MAPK) pathway causing its hyperactivation. Here, we review the clinical and molecular characteristics of this heterogeneous group of diseases, including the possibilities of molecular diagnosis and new therapeutic perspectives.

Immune dysregulation associated with co-occurring germline CBL and SH2B3 variants

Background

CBL syndrome is a RASopathy caused by heterozygous germline mutations of the Casitas B-lineage lymphoma (CBL) gene. It is characterized by heterogeneous clinical phenotype, including developmental delay, facial dysmorphisms, cardiovascular malformations and an increased risk of cancer development, particularly juvenile myelomonocytic leukemia (JMML). Although the clinical phenotype has been progressively defined in recent years, immunological manifestations have not been well elucidated to date.

Methods

We studied the genetic, immunological, coagulative, and clinical profile of a family with CBL syndrome that came to our observation after the diagnosis of JMML, with homozygous CBL mutation, in one of the members.

Results

Variant analysis revealed the co-occurrence of CBL heterozygous mutation (c.1141 T > C) and SH2B3 mutation (c.1697G > A) in two other members. Patients carrying both mutations showed an ALPS-like phenotype characterized by lymphoproliferation, cytopenia, increased double-negative T-cells, impaired Fas-mediated lymphocyte apoptosis, altered cell death in PBMC and low TRECs expression. A coagulative work-up was also performed and showed the presence of subclinical coagulative alterations in patients carrying both mutations.

Conclusion

In the reported family, we described immune dysregulation, as part of the clinical spectrum of CBL mutation with the co-occurrence of SH2B3.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40246-022-00414-y.

International Consensus Classification of Myeloid Neoplasms and Acute Leukemias: integrating morphologic, clinical, and genomic data

The classification of myeloid neoplasms and acute leukemias was last updated in 2016 within a collaboration between the World Health Organization (WHO), the Society for Hematopathology, and the European Association for Haematopathology. This collaboration was primarily based on input from a clinical advisory committees (CACs) composed of pathologists, hematologists, oncologists, geneticists, and bioinformaticians from around the world. The recent advances in our understanding of the biology of hematologic malignancies, the experience with the use of the 2016 WHO classification in clinical practice, and the results of clinical trials have indicated the need for further revising and updating the classification. As a continuation of this CAC-based process, the authors, a group with expertise in the clinical, pathologic, and genetic aspects of these disorders, developed the International Consensus Classification (ICC) of myeloid neoplasms and acute leukemias. Using a multiparameter approach, the main objective of the consensus process was the definition of real disease entities, including the introduction of new entities and refined criteria for existing diagnostic categories, based on accumulated data. The ICC is aimed at facilitating diagnosis and prognostication of these neoplasms, improving treatment of affected patients, and allowing the design of innovative clinical trials.

A Malignant Mimicker: Features of Kikuchi-Fujimoto Disease in the Pediatric Population

BACKGROUND

Kikuchi-Fujimoto disease (KFD) is a rare, benign, and self-limited disease that presents with cervical lymphadenopathy and systemic symptoms. Histologic evaluation is often necessary to differentiate KFD from other entities.

METHODS

Electronic medical records and diagnostic material were reviewed for 14 children diagnosed with KFD and 6 children diagnosed with infectious mononucleosis (IM) from 2013-2021. Four cases of KFD were further characterized using targeted DNA-based next-generation sequencing.

RESULTS

Systemic symptoms were present in 86% (n = 12/14) of KFD patients, the most common being fever. Laboratory values worrisome for malignancy included cytopenia(s) (n = 9/12), elevated ESR and/or CRP (n = 9/12), elevated ferritin (n = 7/7), and elevated LDH (n = 7/10). Histologically, lymph nodes showed characteristic necrotic foci without neutrophils surrounded by MPO+ "crescentic" histiocytes. Immunoblasts and CD123+ plasmacytoid dendritic cells (pDCs) were also increased surrounding the necrosis. IM lymph nodes showed similar features when necrosis was present but increases in pDCs were patchy and rare neutrophils were seen in the necrotic foci. Molecular analysis of 4 KFD cases did not identify pathogenic variants.

CONCLUSION

While the signs/symptoms of KFD are worrisome, there are pathologic features that help differentiate it from potential mimics. We did not identify characteristic molecular features to aid in the work-up of these cases.

EAHP 2020 workshop proceedings, pediatric myeloid neoplasms

The first section of the bone marrow workshop of the European Association of Haematopathology (EAHP) 2020 Virtual Meeting was dedicated to pediatric myeloid neoplasms. The section covered the whole spectrum of myeloid neoplasms, including myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), myelodysplastic/myeloproliferative neoplasms (MDS/MPN), and acute myeloid leukemia (AML). The workshop cases are hereby presented, preceded by an introduction on these overall rare diseases in this age group. Very rare entities such as primary myelofibrosis, pediatric MDS with fibrosis, and MDS/MPN with JMML-like features and t(4;17)(q12;q21); FIP1L1::RARA fusion, are described in more detail.

A case of refractory systemic lupus erythematosus with monocytosis exhibiting somatic KRAS mutation

Background

Systemic lupus erythematosus (SLE), an autoimmune disorder that damages various organ systems, is caused by a combination of genetic and environmental factors. Although germline mutations of several genes are known to cause juvenile SLE, most of the susceptibility genetic variants of adult SLE are common variants of the population, somatic mutations that cause or exacerbate SLE have not been reported. We hereby report a refractory SLE case with monocytosis accompanying somatic KRAS mutation that have been shown to cause lupus-like symptoms.

Case presentation

A 60-year-old female patient who had been diagnosed with SLE was admitted to our hospital. Although prednisolone and tacrolimus treatments had kept her thrombocytopenia and anti-DNA Ab level at bay for more than 4 years, a diagnosis of transverse myelitis was made when she became acutely ill with pleocytosis. Elevated cells (predominately monocytes), protein, IgG, and IL-6 levels were also found in the cerebrospinal fluid (CSF) of the patient. Standard pulse treatments of methylprednisolone, high-dose of prednisolone, and intravenous cyclophosphamide in combination with plasma exchange could not alleviate the refractory neural and autoimmune manifestation. Monocytosis of peripheral blood was also noted. Flow cytometric analysis revealed elevated ratio of CD14+CD16+ atypical monocytes, which excluded the possibility of chronic myelomonocytic leukemia. Lupus-like symptoms with monocytosis reminded us of Ras-associated autoimmune leukoproliferative disorder, and Sanger sequencing of KRAS and NRAS genes from the patients’ peripheral blood mononuclear cells (PBMC), sorted CD3+ lymphocytes and CD14+ monocytes, and cerebrospinal fluid were performed. An activating KRAS somatic mutation was found in the patients’ DNA at the time of encephalomyelitis diagnosis.

Conclusion

Somatic mutations of some genes including KRAS may cause the refractoriness of SLE.

Abnormal B-Cell Maturation and Increased Transitional B Cells in CBL Syndrome

CBL syndrome is a Noonan-like RASopathy with heterogeneous clinical phenotype and predisposition to juvenile myelomonocytic leukemia (JMML). Here we describe two patients with identical germline CBL mutation and clinical and immune-hematological overlapping features with autoimmune lymphoproliferative syndrome (ALPS) and B-cell expansion with NF-κB and T-cell anergy (BENTA) syndrome. Increased immature/transitional B cells can be depicted in CBL syndrome, ALPS, and BENTA. Nonetheless, our patients here described showed peculiar B-cell phenotype due to increased immature/transitional CD34⁺ B cells. This feature differentiates CBL syndrome from BENTA, pointing toward an abnormal proliferation of B-cell early precursors.

Juvenile myelomonocytic leukemia in the molecular era: a clinician's guide to diagnosis, risk stratification, and treatment

Juvenile myelomonocytic leukemia is an overlapping myeloproliferative and myelodysplastic disorder of early childhood . It is associated with a spectrum of diverse outcomes ranging from spontaneous resolution in rare patients to transformation to acute myeloid leukemia in others that is generally fatal. This unpredictable clinical course, along with initially descriptive diagnostic criteria, led to decades of productive international research. Next-generation sequencing now permits more accurate molecular diagnoses in nearly all patients. However, curative treatment is still reliant on allogeneic hematopoietic cell transplantation for most patients, and additional advances will be required to improve risk stratification algorithms that distinguish those that can be observed expectantly from others who require swift hematopoietic cell transplantation.

Autoimmunity in Primary Immunodeficiency Disorders: An Updated Review on Pathogenic and Clinical Implications

During the last years, studies investigating the intriguing association between immunodeficiency and autoimmunity led to the discovery of new monogenic disorders, the improvement in the knowledge of the pathogenesis of autoimmunity, and the introduction of targeted treatments. Autoimmunity is observed with particular frequency in patients with primary antibody deficiencies, such as common variable immunodeficiency (CVID) and selective IgA deficiency, but combined immunodeficiency disorders (CIDs) and disorders of innate immunity have also been associated with autoimmunity. Among CIDs, the highest incidence of autoimmunity is described in patients with autoimmune polyendocrine syndrome 1, LRBA, and CTLA-4 deficiency, and in patients with STAT-related disorders. The pathogenesis of autoimmunity in patients with immunodeficiency is far to be fully elucidated. However, altered germ center reactions, impaired central and peripheral lymphocyte negative selection, uncontrolled lymphocyte proliferation, ineffective cytoskeletal function, innate immune defects, and defective clearance of the infectious agents play an important role. In this paper, we review the main immunodeficiencies associated with autoimmunity, focusing on the pathogenic mechanisms responsible for autoimmunity in each condition and on the therapeutic strategies. Moreover, we provide a diagnostic algorithm for the diagnosis of PIDs in patients with autoimmunity.

Risk of autoimmune diseases in patients with RASopathies: systematic study of humoral and cellular immunity

BACKGROUND

Abnormalities of the immune system are rarely reported in patients affected by RASopathies. Aim of the current study was to investigate the prevalence of immune system dysfunction in a cohort of patients affected by RASopathies.

STUDY DESIGN

A group of 69 patients was enrolled: 60 at the Federico II University, Naples, 7 at University Magna Graecia of Catanzaro, 2 at "Scuola Medica Salernitana", Salerno. An age- and sex-matched control group was also enrolled. Autoimmune disorders were investigated according to international consensus criteria. Immune framework was also evaluated by immunoglobulin levels, CD3, CD4, CD8, CD19, CD56 lymphocyte subpopulations, autoantibodies levels and panel of inflammatory molecules, in both patients and controls.

RESULTS

Frequent upper respiratory tract infections were recorded in 2 patients; pneumonia, psoriasis and alopecia in single patients. Low IgA levels were detected in 8/44 patients (18.18%), low CD8 T cells in 13/35 patients (37.14%). Anti-tg and anti-TPO antibodies were detected in 3/24 patients (12.5%), anti r-TSH in 2 cases (8.33%), all in euthyroidism. Serum IgA and CD8 levels were significantly lower in patients than in controls (p 0.00685; p 0.000656 respectively). All tested patients showed increased inflammatory molecules compared to controls. These findings may anticipate the detection of overt autoimmune disease.

CONCLUSIONS

Patients affected by RASopathies are at risk to develop autoimmune disorders. Routine screening for autoimmunity is recommended in patients with RASopathy.

Hallmarks of Cancers: Primary Antibody Deficiency Versus Other Inborn Errors of Immunity

Inborn Errors of Immunity (IEI) comprise more than 450 inherited diseases, from which selected patients manifest a frequent and early incidence of malignancies, mainly lymphoma and leukemia. Primary antibody deficiency (PAD) is the most common form of IEI with the highest proportion of malignant cases. In this review, we aimed to compare the oncologic hallmarks and the molecular defects underlying PAD with other IEI entities to dissect the impact of avoiding immune destruction, genome instability, and mutation, enabling replicative immortality, tumor-promoting inflammation, resisting cell death, sustaining proliferative signaling, evading growth suppressors, deregulating cellular energetics, inducing angiogenesis, and activating invasion and metastasis in these groups of patients. Moreover, some of the most promising approaches that could be clinically tested in both PAD and IEI patients were discussed.

Primary Immune Regulatory Disorders With an Autoimmune Lymphoproliferative Syndrome-Like Phenotype: Immunologic Evaluation, Early Diagnosis and Management

Primary immune regulatory disorders (PIRD) are associated with autoimmunity, autoinflammation and/or dysregulation of lymphocyte homeostasis. Autoimmune lymphoproliferative syndrome (ALPS) is a PIRD due to an apoptotic defect in Fas-FasL pathway and characterized by benign and chronic lymphoproliferation, autoimmunity and increased risk of lymphoma. Clinical manifestations and typical laboratory biomarkers of ALPS have also been found in patients with a gene defect out of the Fas-FasL pathway (ALPS-like disorders). Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA), we identified more than 600 patients suffering from 24 distinct genetic defects described in the literature with an autoimmune lymphoproliferative phenotype (ALPS-like syndromes) corresponding to phenocopies of primary immunodeficiency (PID) (NRAS, KRAS), susceptibility to EBV (MAGT1, PRKCD, XIAP, SH2D1A, RASGRP1, TNFRSF9), antibody deficiency (PIK3CD gain of function (GOF), PIK3R1 loss of function (LOF), CARD11 GOF), regulatory T-cells defects (CTLA4, LRBA, STAT3 GOF, IL2RA, IL2RB, DEF6), combined immunodeficiencies (ITK, STK4), defects in intrinsic and innate immunity and predisposition to infection (STAT1 GOF, IL12RB1) and autoimmunity/autoinflammation (ADA2, TNFAIP3,TPP2, TET2). CTLA4 and LRBA patients correspond around to 50% of total ALPS-like cases. However, only 100% of CTLA4, PRKCD, TET2 and NRAS/KRAS reported patients had an ALPS-like presentation, while the autoimmunity and lymphoproliferation combination resulted rare in other genetic defects. Recurrent infections, skin lesions, enteropathy and malignancy are the most common clinical manifestations. Some approaches available for the immunological study and identification of ALPS-like patients through flow cytometry and ALPS biomarkers are provided in this work. Protein expression assays for NKG2D, XIAP, SAP, CTLA4 and LRBA deficiencies and functional studies of AKT, STAT1 and STAT3 phosphorylation, are showed as useful tests. Patients suspected to suffer from one of these disorders require rapid and correct diagnosis allowing initiation of tailored specific therapeutic strategies and monitoring thereby improving the prognosis and their quality of life.

Interaction between Ras and Bcl2L12 in B cells suppresses IL-10 expression

The pathogenesis of recurrent tonsillitis is to be further investigated. B cell-derived interleukin (IL)-10 plays a critical role in immune regulation. Ras activation plays an important role in cancer and many immune disorders. This study aims to investigate the role of Ras activation in down regulating IL-10 expression in tonsillar B cells. Surgically removed tonsil tissues were collected from patients with recurrent acute tonsillar inflammation; B cells were isolated from the tonsillar tissues by flow cytometry sorting to be analyzed by the Ras-specific enzyme-linked immunosorbent assay and pertinent immunological approaches. We found that, compared to peripheral B cells (pBC), B cells isolated from the tonsillar tissues with recurrent inflammation (tBC) showed higher Ras activation, lower IL-10 expression and higher Bcl2L12 expression. Bcl2L12 formed a complex with GAP (GTPase activating protein) to prevent Ras from deactivating. The Ras activation triggered the MAPK/Sp1 pathway to promote the Bcl2L12 expression in B cells. Bcl2L12 prevented the IL-10 expression in tBCs, that was counteracted by inhibition of Ras or the Ras signal transduction pathway. In conclusion, Bcl2L12 interacts with Ras activation to compromise immune tolerance in the tonsils by inhibiting the IL-10 expression in tBCs. Inhibition of Bcl2L12 can restore the IL-10 expression in tBCs.

Current Treatment of Juvenile Myelomonocytic Leukemia

Juvenile myelomonocytic leukemia (JMML) is a rare pediatric leukemia characterized by mutations in five canonical RAS pathway genes. The diagnosis is made by typical clinical and hematological findings associated with a compatible mutation. Although this is sufficient for clinical decision-making in most JMML cases, more in-depth analysis can include DNA methylation class and panel sequencing analysis for secondary mutations. NRAS-initiated JMML is heterogeneous and adequate management ranges from watchful waiting to allogeneic hematopoietic stem cell transplantation (HSCT). Upfront azacitidine in KRAS patients can achieve long-term remissions without HSCT; if HSCT is required, a less toxic preparative regimen is recommended. Germline CBL patients often experience spontaneous resolution of the leukemia or exhibit stable mixed chimerism after HSCT. JMML driven by PTPN11 or NF1 is often rapidly progressive, requires swift HSCT and may benefit from pretransplant therapy with azacitidine. Because graft-versus-leukemia alloimmunity is central to cure high risk patients, the immunosuppressive regimen should be discontinued early after HSCT.

RASopathies: from germline mutations to somatic and multigenic diseases

The RAS-RAF-MEK-ERK signaling pathway is vital for different cellular mechanisms including cell proliferation, differentiation and apoptosis. This importance is highlighted by the high prevalence of mutations in RAS or related proteins of the pathway in cancers. More recently, development abnormalities have been linked to various germline mutations in this pathway and called RASopathies. Interestingly, rare disorders such as RAS-associated leukoproliferative diseases and histiocytosis have also been recently linked to multiple mutations in the same pathway, sometimes with the same mutation. This review will focus on germline RASopathies and rare somatic RASopathies and focus on how gain-of-function mutations in the same pathway can lead to various diseases.

Lymphadenopathy at the crossroad between immunodeficiency and autoinflammation: An intriguing challenge

Lymphadenopathies can be part of the clinical spectrum of several primary immunodeficiencies, including diseases with immune dysregulation and autoinflammatory disorders, as the clinical expression of benign polyclonal lymphoproliferation, granulomatous disease or lymphoid malignancy. Lymphadenopathy poses a significant diagnostic dilemma when it represents the first sign of a disorder of the immune system, leading to a consequently delayed diagnosis. Additionally, the finding of lymphadenopathy in a patient with diagnosed immunodeficiency raises the question of the differential diagnosis between benign lymphoproliferation and malignancies. Lymphadenopathies are evidenced in 15–20% of the patients with common variable immunodeficiency, while in other antibody deficiencies the prevalence is lower. They are also evidenced in different combined immunodeficiency disorders, including Omenn syndrome, which presents in the first months of life. Interestingly, in the activated phosphoinositide 3‐kinase delta syndrome, autoimmune lymphoproliferative syndrome, Epstein–Barr virus (EBV)‐related lymphoproliferative disorders and regulatory T cell disorders, lymphadenopathy is one of the leading signs of the entire clinical picture. Among autoinflammatory diseases, the highest prevalence of lymphadenopathies is observed in patients with periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) and hyper‐immunoglobulin (Ig)D syndrome. The mechanisms underlying lymphoproliferation in the different disorders of the immune system are multiple and not completely elucidated. The advances in genetic techniques provide the opportunity of identifying new monogenic disorders, allowing genotype–phenotype correlations to be made and to provide adequate follow‐up and treatment in the single diseases. In this work, we provide an overview of the most relevant immune disorders associated with lymphadenopathy, focusing on their diagnostic and prognostic implications.

Inherited deficiency of stress granule ZNFX1 in patients with monocytosis and mycobacterial disease

Human inborn errors of IFN-γ underlie mycobacterial disease, due to insufficient IFN-γ production by lymphoid cells, impaired myeloid cell responses to this cytokine, or both. We report four patients from two unrelated kindreds with intermittent monocytosis and mycobacterial disease, including bacillus Calmette-Guérin-osis and disseminated tuberculosis, and without any known inborn error of IFN-γ. The patients are homozygous for ZNFX1 variants (p.S959* and p.E1606Rfs*10) predicted to be loss of function (pLOF). There are no subjects homozygous for pLOF variants in public databases. ZNFX1 is a conserved and broadly expressed helicase, but its biology remains largely unknown. It is thought to act as a viral double-stranded RNA sensor in mice, but these patients do not suffer from severe viral illnesses. We analyze its subcellular localization upon overexpression in A549 and HeLa cell lines and upon stimulation of THP1 and fibroblastic cell lines. We find that this cytoplasmic protein can be recruited to or even induce stress granules. The endogenous ZNFX1 protein in cell lines of the patient homozygous for the p.E1606Rfs*10 variant is truncated, whereas ZNFX1 expression is abolished in cell lines from the patients with the p.S959* variant. Lymphocyte subsets are present at normal frequencies in these patients and produce IFN-γ normally. The hematopoietic and nonhematopoietic cells of the patients tested respond normally to IFN-γ. Our results indicate that human ZNFX1 is associated with stress granules and essential for both monocyte homeostasis and protective immunity to mycobacteria.

Pediatric Neoplasms Presenting with Monocytosis

PURPOSE OF REVIEW

Juvenile myelomonocytic leukemia (JMML) is a rare but severe pediatric neoplasm with hematopoietic stem cell transplant as its only established curative option. The development of targeted therapeutics for JMML is being guided by an understanding of the pathobiology of this condition. Here, we review JMML with an emphasis on genetics in order to (i) demonstrate the relationship between JMML genotype and clinical phenotype and (ii) explore potential genetic targets of novel JMML therapies.

RECENT FINDINGS

DNA hypermethylation studies have demonstrated consistently that methylation is related to disease severity. Increasing understanding of methylation in JMML may open the door to novel therapies, such as DNA methyltransferase inhibitors. The PI3K/AKT/MTOR, JAK/STAT, and RAF/MEK/ERK pathways are being investigated as therapeutic targets for JMML. Future therapy for JMML will be driven by an increased understanding of pathobiology. Targeted therapeutic approaches hold potential for improving outcomes in patients with JMML.

Idiopathic splenomegaly in childhood and the spectrum of RAS-associated lymphoproliferative disease: a case report

Background

KRAS (KRAS proto-oncogene, GTPase; OMIM: 190,070) encodes one of three small guanosine triphosphatase proteins belonging to the RAS family. This group of proteins is responsible for cell proliferation, differentiation and inhibition of apoptosis. Gain-of-function variants in KRAS are commonly found in human cancers. Non-malignant somatic KRAS variants underlie a subset of RAS-associated autoimmune leukoproliferative disorders (RALD). RALD is characterized by splenomegaly, persistent monocytosis, hypergammaglobulinemia and cytopenia, but can also include autoimmune features and lymphadenopathy. In this report, we describe a non-malignant somatic variant in KRAS with prominent clinical features of massive splenomegaly, thrombocytopenia and lymphopenia.

Case presentation

A now-11-year-old girl presented in early childhood with easy bruising and bleeding, but had an otherwise unremarkable medical history. After consulting for the first time at 5 years of age, she was discovered to have massive splenomegaly. Clinical follow-up revealed thrombocytopenia, lymphopenia and increased polyclonal immunoglobulins and C-reactive protein. The patient had an unremarkable bone marrow biopsy, flow cytometry showed no indication of expanded double negative T-cells, while malignancy and storage disorders were also excluded. When the patient was 8 years old, whole exome sequencing performed on DNA derived from whole blood revealed a heterozygous gain-of-function variant in KRAS (NM_004985.5:c.37G > T; (p.G13C)). The variant was absent from DNA derived from a buccal swab and was thus determined to be somatic.

Conclusions

This case of idiopathic splenomegaly in childhood due to a somatic variant in KRAS expands our understanding of the clinical spectrum of RAS-associated autoimmune leukoproliferative disorder and emphasizes the value of securing a molecular diagnosis in children with unusual early-onset presentations with a suspected monogenic origin.

Clinical and Cytometric Study of Immune Involvement in a Heterogeneous Cohort of Subjects With RASopathies and mTORopathies

RASopathies and mTORopathies are groups of genetic syndromes associated with increased activation of the RAS-MAPK or the PI3K-AKT-mTOR pathway, resulting in altered cell proliferation during embryonic and postnatal development. The RAS-MAPK and the PI3K-AKT-mTOR pathways are connected to each other and play a crucial role in adaptive immunity. However, with the exception of Activated PI3K delta syndrome (APDS), immune function has not been deeply studied in these disorders. We collected clinical and immunophenotypic data of a cohort of patients with RASopathies and mTORopathies. Overall, we enrolled 47 patients (22 females, 25 males, age 2-40 years): 33 with neurofibromatosis type 1, 11 Noonan syndrome and 3 Bannayan-Riley-Ruvalcaba syndrome. 8 patients reported a history of invasive infections requiring hospitalization and intravenous antibiotic therapy. Only 3 patients reported a history of unusual, difficult-to-treat or deep-seated infection. Adenotonsillectomy was performed in 11 patients (24%). However, in most cases (83%) patients' parents did not perceive their child as more prone to infections than their peers. Lymphocyte subpopulations were analyzed in 37 of the 47 patients (16 female, 21 males, age 1-40 years). Among the studied lymphocyte subsets, the only consistent alteration regarded an increased percentage of immature B cells (recent bone marrow emigrants) in 34 out of 37 (91,9%) patients, and an increased percentage of double negative T cells in 9 patients. In conclusion, although borderline immune abnormalities were present in a significant proportion of subjects and adenotonsillectomy was performed more frequently than expected for the general population, no major immune disturbance was found in this cohort of patients.

Immunologic evaluation and genetic defects of apoptosis in patients with autoimmune lymphoproliferative syndrome (ALPS)

Apoptosis plays an important role in controlling the adaptive immune response and general homeostasis of the immune cells, and impaired apoptosis in the immune system results in autoimmunity and immune dysregulation. In the last 25 years, inherited human diseases of the Fas-FasL pathway have been recognized. Autoimmune lymphoproliferative syndrome (ALPS) is an inborn error of immunity, characterized clinically by nonmalignant and noninfectious lymphoproliferation, autoimmunity, and increased risk of lymphoma due to a defect in lymphocyte apoptosis. The laboratory hallmarks of ALPS are an elevated percentage of T-cell receptor αβ double negative T cells (DNTs), elevated levels of vitamin B12, soluble FasL, IL-10, IL-18 and IgG, and defective in vitro Fas-mediated apoptosis. In order of frequency, the genetic defects associated with ALPS are germinal and somatic ALPS-FAS, ALPS-FASLG, ALPS-CASP10, ALPS-FADD, and ALPS-CASP8. Partial disease penetrance and severity suggest the combination of germline and somatic FAS mutations as well as other risk factor genes. In this report, we summarize human defects of apoptosis leading to ALPS and defects that are known as ALPS-like syndromes that can be clinically similar to, but are genetically distinct from, ALPS. An efficient genetic and immunological diagnostic approach to patients suspected of having ALPS or ALPS-like syndromes is essential because this enables the establishment of specific therapeutic strategies for improving the prognosis and quality of life of patients.

Polyclonal B-cell lymphocytosis in English bulldogs

Background

English bulldogs disproportionally develop an expansion of small B‐cells, which has been interpreted as B‐cell chronic lymphocytic leukemia (BCLL). However, clonality testing in these cases has often not been supportive of neoplasia.

Hypothesis

English bulldogs have a syndrome of nonneoplastic B‐cell expansion.

Animals

Eighty‐four English bulldogs with small‐sized CD21+ B‐cell lymphocytosis in the blood as determined by flow cytometry.

Methods

This is a retrospective study. We characterized this syndrome by assessing B‐cell clonality, clinical presentation, flow cytometric features, and immunoglobulin gammopathy patterns. We identified 84 cases with CD21+ lymphocytosis among 195 English bulldogs with blood samples submitted to the Colorado State University‐Clinical Immunology laboratory for immunophenotyping between 2010 and 2019. Flow cytometry features were compared to normal B‐cells and BCLL cases. PCR for antigen receptor rearrangements (PARR) by multiple immunoglobulin primers was performed to assess B‐cell clonality. A subset of cases with gammopathy were examined by protein electrophoresis, immunofixation, and immunoglobulin subclass ELISA quantification.

Results

Seventy percent (58/83) of cases had polyclonal or restricted polyclonal immunoglobulin gene rearrangements, suggesting nonmalignant B‐cell expansion. The median age of all dogs in the study was 6.8 years and 74% were male. The median (range) lymphocyte count was 22 400/μL (2000‐384 400/μL) and B‐cells had low expression of class II MHC and CD25. Splenomegaly or splenic masses were detected in 57% (26/46) of cases and lymphadenopathy in 11% (7/61). Seventy‐one percent (52/73) of cases had hyperglobulinemia and 77% (23/30) with globulin characterization had IgA ± IgM polyclonal or restricted polyclonal gammopathy patterns.

Conclusions and Clinical Importance

Polyclonal B‐cell lymphocytosis in English bulldogs is characterized by low B‐cell class II MHC and CD25 expression, splenomegaly and hyperglobulinemia consisting of increased IgA ± IgM. We hypothesize that this syndrome has a genetic basis.

Clinical Spectrum of Ras-Associated Autoimmune Leukoproliferative Disorder (RALD)

Ras-associated autoimmune leukoproliferative disorder (RALD) is a clinical entity initially identified in patients evaluated for an autoimmune lymphoproliferative syndrome (ALPS)-like phenotype. It remains a matter of debate whether RALD is a chronic and benign lymphoproliferative disorder or a pre-malignant condition. We report the case of a 7-year-old girl diagnosed with RALD due to somatic KRAS mutation who progressed to a juvenile myelomonocytic leukemia phenotype and finally evolved into acute myeloid leukemia. The case report prompted a literature review by a search for all RALD cases published in PubMed and Embase. We identified 27 patients with RALD. The male-to-female ratio was 1:1 and median age at disease onset was 2 years (range 3 months-36 years). Sixteen patients (59%) harbored somatic mutations in KRAS and 11 patients (41%) somatic mutations in NRAS. The most common features were splenomegaly (26/27 patients), autoimmune cytopenia (15/16 patients), monocytosis (18/24 patients), pericarditis (6 patients), and skin involvement (4 patients). Two patients went on to develop a hematopoietic malignancy. In summary, the current case documents an additional warning about the long-term risk of malignancy in RALD.

Immunophenotypic characteristics of juvenile myelomonocytic leukaemia and their relation with the molecular subgroups of the disease

The diagnosis of juvenile myelomonocytic leukaemia (JMML) is based on clinical, laboratory and molecular features but immunophenotyping [multiparametric flow cytometry (MFC)] has not been used routinely. In the present study, we describe the flow cytometric features at diagnosis with special attention to the distribution of monocytic subsets and the relation between MFC and molecular subgroups. MFC was performed with an eight-colour platform based on Euroflow. We studied 33 JMML cases. CD34⁺ /CD117⁺ /CD13⁺ cells >2% was found in 25 cases, and 51·5% presented an aberrant expression of CD7. A decrease of CD34⁺ /CD19⁺ /CD10⁺ cells was seen in eight cases and in four they were absent. The granulocytic population had a decreased side scatter in 29 cases. Bone marrow monocytic precursors were increased in 28 patients, with a decrease in classical monocytes (median 80·7%) and increase in CD16⁺ (intermediate and non-classical). A more pronounced increase in myeloid CD34⁺ cells was seen in patients with Neurofibromatosis type 1 (NF1) and tyrosine-protein phosphatase non-receptor type 11 (PTPN11), with aberrant CD7 expression in four of six and 10/12 patients respectively. Thus, JMML shows an immunophenotypic profile similar to myelodysplastic syndromes, and a different monocyte subset distribution when compared with chronic MML. MFC proved to be an important diagnostic tool that can help in differential diagnosis with other clonal diseases with monocytosis.

A Case of Uveitis in a Patient With Juvenile Myelomonocytic Leukemia Successfully Treated With Adalimumab

Patients with juvenile myelomonocytic leukemia due to germline CBL mutation (10% to 15%) may have a subacute course occasionally associated with autoimmune disorders, which may resemble RAS-associated autoimmune lymphoproliferative disorder. In both conditions, prognosis and standard treatment for autoimmune phenomena remain poorly understood. We report the case of a 7-year-old boy with juvenile myelomonocytic leukemia with severe steroid-dependent uveitis, who did not respond to several therapeutic attempts with immunosuppressant agents, including sirolimus, and was finally successfully treated with adalimumab. This case offers further insight into the management of autoimmune disorders in the context of predisposing genetic conditions.

After 95 years, it's time to eRASe JMML

Juvenile myelomonocytic leukaemia (JMML) is a rare clonal disorder of early childhood. Constitutive activation of the RAS pathway is the initial event in JMML. Around 90% of patients diagnosed with JMML carry a mutation in the PTPN11, NRAS, KRAS, NF1 or CBL genes. It has been demonstrated that after this first genetic event, an additional somatic mutation or epigenetic modification is involved in disease progression. The available genetic and clinical data have enabled researchers to establish relationships between JMML and several clinical conditions, including Noonan syndrome, Ras-associated lymphoproliferative disease, and Moyamoya disease. Despite scientific progress and the development of more effective treatments, JMML is still a deadly disease: the 5-year survival rate is ~50%. Here, we report on recent research having led to a better understanding of the genetic and molecular mechanisms involved in JMML.

Primary immunodeficiencies: novel genes and unusual presentations

Recent advances in genomics have greatly expanded the spectrum of primary immune deficiencies (PIDs). Along with the identification of pathogenic variants in novel genes, distinct phenotypes have been associated with different variants in the same gene. Although PIDs have been historically defined based on increased susceptibility to infections, immune dysregulation has emerged as a frequent and in some cases, predominant phenotype. Autoimmune cytopenias with onset in childhood, lasting longer than 12 months, and affecting multiple lineages should raise the suspicion of a possible PID with monogenic origin. Characterization of the various molecular and cellular mechanisms responsible for these unusual manifestations of PIDs, although at times resource intensive, may allow for targeted intervention in many of them.

FAS and RAS related Apoptosis defects: From autoimmunity to leukemia

The human adaptive immune system recognizes almost all the pathogens that we encounter and all the tumor antigens that may arise during our lifetime. Primary immunodeficiencies affecting lymphocyte development or function therefore lead to severe infections and tumor susceptibility. Furthermore, the fact that autoimmunity is a frequent feature of primary immunodeficiencies reveals a third function of the adaptive immune system: its self-regulation. Indeed, the generation of a broad repertoire of antigen receptors (via a unique strategy of random somatic rearrangements of gene segments in T cell and B cell receptor loci) inevitably creates receptors with specificity for self-antigens and thus leads to the presence of autoreactive lymphocytes. There are many different mechanisms for controlling the emergence or action of autoreactive lymphocytes, including clonal deletion in the primary lymphoid organs, receptor editing, anergy, suppression of effector lymphocytes by regulatory lymphocytes, and programmed cell death. Here, we review the genetic defects affecting lymphocyte apoptosis and that are associated with lymphoproliferation and autoimmunity, together with the role of somatic mutations and their potential involvement in more common autoimmune diseases.

18F-FDG PET Imaging Features of Patients With Autoimmune Lymphoproliferative Syndrome

INTRODUCTION

Autoimmune lymphoproliferative syndrome (ALPS) is a rare immune dysregulatory condition, usually presenting in childhood with massive lymphadenopathy, splenomegaly, and an increased incidence of lymphoma. Methods to differentiate between benign ALPS adenopathy and lymphoma are needed. To this end, we evaluated the usefulness of FDG PET.

METHODS

We prospectively evaluated 76 ALPS/ALPS-like patients including FS-7-associated surface antigen (FAS) germline mutation with (n = 4) and without lymphoma (n = 50), FAS-somatic (n = 6), ALPS-unknown (n = 6), and others (n = 10) who underwent FDG PET. Uptakes in 14 nodal sites, liver, and spleen were determined.

RESULTS

In 76 ALPS patients, FDG PET showed uptake in multiple nodal sites in all but 1 patient. The highest SUVmax values in FAS mutation without lymphoma, FAS mutation with lymphoma, FAS somatic, ALPS-unknown, and other genetic mutations were a median (range) 9.2 (4.3-25), 16.2 (10.7-37.2), 7.6 (4.6-18.1), 11.5 (4.8-17.2), and 5.5 (0-15.3), respectively. Differences between uptake in the FAS group with and without lymphoma were statistically significant, but overlapped, making discrimination between individuals with/without lymphoma impossible. The spleen:liver uptake ratio was greater than 1 in 82% of patients.

CONCLUSIONS

While statistically significant differences were observed in FAS mutation ALPS with and without lymphoma, the significant overlap in FDG uptake and visual appearance in many patients prevents discrimination between patients with and without lymphoma. Similar patterns of FDG biodistribution were noted between the various ALPS subgroups.

Sustained remission with azacitidine monotherapy and an aberrant precursor B-lymphoblast population in juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) has a poor prognosis in general, with hematopoietic stem cell transplant (HSCT) remaining the standard of care for cure. The hypomethylating agent, azacitidine, has been used as a bridging therapy to transplant. However, no patients have been treated with azacitidine without an HSCT post azacitidine. We report on an infant with JMML with somatic KRAS G12A mutation and monosomy 7 who achieved sustained remission following azacitidine monotherapy. He also developed an aberrant B-lymphoblast population which declined with similar kinetics as his JMML-associated abnormalities, suggesting that a B-lymphoblast population in JMML does not always progress to acute leukemia.

An updated review on phenocopies of primary immunodeficiency diseases

Primary immunodeficiency diseases (PIDs) refer to a heterogenous group of disorders characterized clinically by increased susceptibility to infections, autoimmunity and increased risk of malignancies.

These group of disorders present with clinical manifestations similar to PIDs with known genetic defects but have either no genetic defect or have a somatic mutation and thus have been labelled as “Phenocopies of PIDs”. These diseases have been further subdivided into those associated with somatic mutations and those associated with presence of auto-antibodies against various cytokines.

In this review, we provide an update on clinical manifestations, diagnosis and management of these diseases.

RAS-associated Autoimmune Leukoproliferative disease (RALD) manifested with early-onset SLE-like syndrome: a case series of RALD in Chinese children

BACKGROUND

Primary immunodeficiency diseases (PIDs) patients may show systemic lupus erythematosus (SLE)-like autoimmunity disorders, such as cytopenias, as well as polyarthritis, which leads to concerns of misdiagnosis. We diagnosed three RALD cases between 2015 and 2018, who were suspected as SLE and summarized clinical characteristics.

METHODS

We collected and analyzed the clinical data of the 3 cases. DNA was extracted from the patients' and their parents' peripheral blood as well as oral mucosa cells, hair follicles, and nails. Genes were detected with the application of gene trapping high-throughput sequencing using PIDs panel and suspicious gene or mutation was further verified by Sanger sequencing.

RESULTS

1.

CLINICAL FEATURES

On the one hand, the patients presented with severe thrombocytopenia, facial erythema, arthritis, positive autoantibodies and other manifestations, supporting the diagnosis of SLE. On the other hand, symptoms including early onset ages, recurrent infections, lymphadenopathy, hepatosplenomegaly, monocytosis and hypergammaglobulinemia, were common observed in PIDs. 2. Gene analysis: NRAS mutations (c.38G > A, p.G13D or c.37G > T, p.G13C) were found in the blood of the patients. Besides, the same set of mutations was detected in buccal mucosa of patient 1 and nails of patient 3 while the frequency was much lower. However, no mutation was found in other tissues or in their parents' blood. Consequently, they were NRAS somatic mutated RALD.

CONCLUSIONS

For those early-onset SLE-like patients with predominant hematologic disorders, monocytosis, recurrent infectious history, accompanied with hepatosplenomegaly and lymphadenopathy, a genetic screening of PIDs might be required.

Superficial and Deep Cutaneous Involvement by RAS-Associated Autoimmunne Leukoproliferative Disease (RALD Cutis): A Histologic Mimicker of Histiocytoid Sweet Syndrome

RAS-associated autoimmune leukoproliferative disease (RALD) is a recently described noninfectious and nonmalignant clinical syndrome characterized by autoimmune disorders, massive splenomegaly, modest lymphadenopathy, and monocytosis. On the molecular level, RALD is defined by somatic mutations of either NRAS or KRAS gene in a subset of hematopoietic cells. To date, there is a dearth of well-documented histopathologic description of cutaneous involvement by RALD in the literature. In the current case report, a 43-year-old female patient with a history of RALD presented with clinical pictures of sepsis and an erythematous rash in the left lower extremity. Histologic examination revealed a dense perivascular and interstitial infiltrate of immature myeloid cells admixed with scattered neutrophils involving the dermis and subcutaneous adipose tissue, imparting a panniculitis-like histologic pictures. There was a strong angiocentric propensity of the immature hematopoietic cells as well as extensive extravasation of red blood cells, even in the subcutaneous adipose tissue. Immunohistochemically, the immature hematopoietic cells were positive for CD43, CD4, and CD68, but negative for CD34, CD117, and myeloperoxidase. Overall, the histologic and cytologic findings were highly reminiscent of histiocytoid Sweet syndrome. Review of the English literature revealed cutaneous involvements by RALD only in patients with KRAS mutation compared with none of its NRAS counterparts. However, larger clinicopathologic studies on cutaneous involvement by RALD are warranted. The term "RALD cutis" with its histologic and molecular features is suggested to serve as a potential groundwork for future studies of this rare phenomenon.

Pediatric Evans syndrome is associated with a high frequency of potentially damaging variants in immune genes

Evans syndrome (ES) is a rare severe autoimmune disorder characterized by the combination of autoimmune hemolytic anemia and immune thrombocytopenia. In most cases, the underlying cause is unknown. We sought to identify genetic defects in pediatric ES (pES), based on a hypothesis of strong genetic determinism. In a national, prospective cohort of 203 patients with early-onset ES (median [range] age at last follow-up: 16.3 years ([1.2-41.0 years]) initiated in 2004, 80 nonselected consecutive individuals underwent genetic testing. The clinical data were analyzed as a function of the genetic findings. Fifty-two patients (65%) received a genetic diagnosis (the M+ group): 49 carried germline mutations and 3 carried somatic variants. Thirty-two (40%) had pathogenic mutations in 1 of 9 genes known to be involved in primary immunodeficiencies (TNFRSF6, CTLA4, STAT3, PIK3CD, CBL, ADAR1, LRBA, RAG1, and KRAS), whereas 20 patients (25%) carried probable pathogenic variants in 16 genes that had not previously been reported in the context of autoimmune disease. Lastly, no genetic abnormalities were found in the remaining 28 patients (35%, the M- group). The M+ group displayed more severe disease than the M- group, with a greater frequency of additional immunopathologic manifestations and a greater median number of lines of treatment. Six patients (all from the M+ group) died during the study. In conclusion, pES was potentially genetically determined in at least 65% of cases. Systematic, wide-ranging genetic screening should be offered in pES; the genetic findings have prognostic significance and may guide the choice of a targeted treatment.