Genetic etiologies of severe congenital neutropenia

Case report: Granulocyte-macrophage colony-stimulating factor sargramostim did not rescue the neutrophil phenotype in two patients with JAGN1-mutant severe congenital neutropenia

Background

Homozygous or compound heterozygous mutations in JAGN1 cause severe congenital neutropenia. JAGN1-mutant patients present with severe early-onset bacterial infections and most have been described as low-responders to recombinant granulocyte colony-stimulating factor (G-CSF) therapy. In a murine, hematopoietic JAGN1 knockout model, which displays susceptibility to Candida albicans infection in the absence of neutropenia, treatment with granulocyte-macrophage-CSF (GM-CSF) was able to restore the functional defect of neutrophils.

Patients

We present two unrelated patients with biallelic JAGN1 mutations, who were both treated with subcutaneous GM-CSF (sargramostim) after treatment failure to G-CSF. The first patient was an 18-year-old pregnant woman who received GM-CSF at 12 weeks of gestation up to a dose of 10 µg/kg/d for 7 days. The second patient was a 5-month-old girl who received GM-CSF for a total of 9 days at a dose of up to 20 µg/kg/d. GM-CSF did not increase neutrophil counts in our patients. Treatment was stopped when neutrophil numbers declined further, no beneficial effect was noticed, and patients presented with infections. No adverse effects were observed in either patient and the fetus. Both patients ultimately underwent successful hematopoietic stem cell transplantation.

Discussion

Both patients showed a high recurrence rate of severe infections on G-CSF treatment. GM-CSF therapy did not ameliorate the clinical phenotype, in contrast to the improvement of neutrophil function observed in the JAGN1 mouse model. No major additional extra-hematopoietic manifestations were evident in our patients.

Conclusion

In two unrelated patients, GM-CSF did not have any beneficial effect on neutrophil counts. Patients with JAGN1-mutant SCN with reduced G-CSF responsiveness and elevated infection rate should be evaluated early for stem cell transplantation.

Oral health management in children with severe congenital neutropenia with periodontitis: Case report

RATIONALE

Severe congenital neutropenia (SCN) is a rare and heterogeneous genetic disease. By describing the diagnosis and treatment of a child with SCN and periodontitis, this case provides a reference for the oral health management of a child with SCN and periodontitis.

PATIENT CONCERNS

We describe a boy with clinical manifestations of oral bleeding, neutropenia, recurrent fever, and other recurrent infections. The absolute neutrophil count (ANC) was <0.50 × 109/L most of the time. Morphological examination of bone marrow cells showed active granulocyte hyperplasia and dysmaturation.

DIAGNOSES

According to the clinical manifestations, hematological examination and gene detection results, the child was diagnosed as SCN with chronic periodontitis.

INTERVENTIONS

Periodontal treatment was performed after informed consent was obtained from the child guardian. These included supragingival and subgingival cleaning, hydrogen peroxide and saline irrigation, placement of iodoglycerin in the gingival sulcus, and oral hygiene instruction. Hematopoietic stem cell transplantation (HSCT) was performed later.

OUTCOMES

One month after initial periodontal treatment, oral hygiene was well maintained and gingival swelling had subsided. Probing depth (PD) index on periodontal probing and bleeding was significantly reduced. However, there was no significant change in blood routine and other indicators before and after periodontal treatment.

CONCLUSION

Once SCN is diagnosed, individualized treatment plans can be developed according to the characteristics of the disease and its impact on oral health, which can effectively control the interaction between SCN and periodontal disease and reduce the occurrence of serious infection.

Inherited bone marrow failure syndromes and germline predisposition to myeloid neoplasia: A practical approach for the pathologist

The diagnostic work up and surveillance of germline disorders of bone marrow failure and predisposition to myeloid malignancy is complex and involves correlation between clinical findings, laboratory and genetic studies, and bone marrow histopathology. The rarity of these disorders and the overlap of clinical and pathologic features between primary and secondary causes of bone marrow failure, acquired aplastic anemia, and myelodysplastic syndrome may result in diagnostic uncertainty. With an emphasis on the pathologist's perspective, we review diagnostically useful features of germline disorders including Fanconi anemia, Shwachman-Diamond syndrome, telomere biology disorders, severe congenital neutropenia, GATA2 deficiency, SAMD9/SAMD9L diseases, Diamond-Blackfan anemia, and acquired aplastic anemia. We discuss the distinction between baseline morphologic and genetic findings of these disorders and features that raise concern for the development of myelodysplastic syndrome.

Historical Cohort of Severe Congenital Neutropenia in Iran: Clinical Course, Laboratory Evaluation, Treatment, and Survival

INTRODUCTION

Severe congenital neutropenia (SCN) is one of the primary immunodeficiency diseases developed by genetic alterations. Mutations in several genes including HAX-1 , G6PC3 , jagunal , and VPS45 account for autosomal recessive SCN.

PATIENTS AND METHODS

Patients with SCN registered in the Iranian Primary Immunodeficiency Registry and referred to our clinic at the Children's Medical Center were reviewed.

RESULTS

Thirty-seven eligible patients with a mean age of 28.51 ± 24.38 months at the time of diagnosis were included. Nineteen cases had consanguineous parents and 10 cases had confirmed or unconfirmed positive family history. The most prevalent infectious symptoms were oral infections followed by respiratory infections. We identified HAX-1 mutation in 4, ELANE mutation in 4 cases, G6PC3 mutation in 1, and WHIM syndrome in 1 case. Other patients remained genetically unclassified. After the median follow-up of 36 months from the time of diagnosis, the overall survival was 88.88%. The mean event-free survival was 185.84 months (95% CI: 161.02, 210.66).

DISCUSSION

Autosomal recessive SCN is more common in countries with high rates of consanguinity like Iran. The genetic classification was possible only for a few patients in our study. This might suggest that there are other autosomal recessive genes causative of neutropenia that have yet to be described.

Inherited Susceptibility to Hematopoietic Malignancies in the Era of Precision Oncology

As germline predisposition to hematopoietic malignancies has gained increased recognition and attention in the field of oncology, it is important for clinicians to use a systematic framework for the identification, management, and surveillance of patients with hereditary hematopoietic malignancies (HHMs). In this article, we discuss strategies for identifying individuals who warrant diagnostic evaluation and describe considerations pertaining to molecular testing. Although a paucity of prospective data is available to guide clinical monitoring of individuals harboring pathogenic variants, we provide recommendations for clinical surveillance based on consensus opinion and highlight current advances regarding the risk of progression to overt malignancy in HHM variant carriers. We also discuss the prognosis of HHMs and considerations surrounding the utility of allogeneic stem-cell transplantation in these individuals. We close with an overview of contemporary issues at the intersection of HHMs and precision oncology.

A Novel Intronic Mutation Reduces HAX1 Level and is Associated With Severe Congenital Neutropenia

Severe congenital neutropenia (SCN) is a rare disease. Autosomal recessive forms of SCN are more frequent in countries where consanguineous marriages are common. In this report, we describe a 54-day-old female with neutropenia who presented with ecthyma gangrenosum. Clinical exome sequencing was used to identify the mutation. HAX1 messenger RNA and isoforms were examined by real-time quantitative and conventional polymerase chain reaction. Bone marrow aspiration was stained by hematoxylin and eosin. Granulocytes were tested for apoptosis upon H2O2 exposure. T-cell proliferation was tested by flow cytometry. Clinical exome sequencing revealed a novel homozygous acceptor splice site mutation in intron 3 of HAX1 (c.505-1G>C), which reduced both isoforms A and B of HAX1 messenger RNA. The Western blot studies showed a complete absence of HAX1 protein. The purified neutrophils from the patient showed increased apoptosis upon H2O2 exposure, whereas T-cell proliferative responses to various stimuli were intact. The patient was treated with combined antibiotics, filgrastim, and placed on antibiotics prophylaxis. To the best of our knowledge, our data provide the first experimental evidence for HAX1 deficiency because of a splice site mutation. Although 3 other splice site variants have been deposited in databases, functional studies were missing. This novel variant of HAX1 may explain the SCN and secondary infections in our patients.

Utility of clinical comprehensive genomic characterization for diagnostic categorization in patients presenting with hypocellular bone marrow failure syndromes

Bone marrow failure (BMF) related to hypoplasia of hematopoietic elements in the bone marrow is a heterogeneous clinical entity with a broad differential diagnosis including both inherited and acquired causes. Accurate diagnostic categorization is critical to optimal patient care and detection of genomic variants in these patients may provide this important diagnostic and prognostic information. We performed real-time, accredited (ISO15189) comprehensive genomic characterization including targeted sequencing and whole exome sequencing in 115 patients with BMF syndrome (median age 24 years, range 3 months - 81 years). In patients with clinical diagnoses of inherited BMF syndromes, acquired BMF syndromes or clinically unclassifiable BMF we detected variants in 52% (12/23), 53% (25/47) and 56% (25/45) respectively. Genomic characterization resulted in a change of diagnosis in 30/115 (26%) including the identification of germline causes for 3/47 and 16/45 cases with pre-test diagnoses of acquired and clinically unclassifiable BMF respectively. The observed clinical impact of accurate diagnostic categorization included choice to perform allogeneic stem cell transplantation, disease-specific targeted treatments, identification of at-risk family members and influence of sibling allogeneic stem cell donor choice. Multiple novel pathogenic variants and copy number changes were identified in our cohort including in TERT, FANCA, RPS7 and SAMD9. Whole exome sequence analysis facilitated the identification of variants in two genes not typically associated with a primary clinical manifestation of BMF but also demonstrated reduced sensitivity for detecting low level acquired variants. In conclusion, genomic characterization can improve diagnostic categorization of patients presenting with hypoplastic BMF syndromes and should be routinely performed in this group of patients.

Primary Immunodeficiencies With Defects in Innate Immunity: Focus on Orofacial Manifestations

The field of primary immunodeficiencies (PIDs) is rapidly evolving. Indeed, the number of described diseases is constantly increasing thanks to the rapid identification of novel genetic defects by next-generation sequencing. PIDs are now rather referred to as “inborn errors of immunity” due to the association between a wide range of immune dysregulation-related clinical features and the “prototypic” increased infection susceptibility. The phenotypic spectrum of PIDs is therefore very large and includes several orofacial features. However, the latter are often overshadowed by severe systemic manifestations and remain underdiagnosed. Patients with impaired innate immunity are predisposed to a variety of oral manifestations including oral infections (e.g., candidiasis, herpes gingivostomatitis), aphthous ulcers, and severe periodontal diseases. Although less frequently, they can also show orofacial developmental abnormalities. Oral lesions can even represent the main clinical manifestation of some PIDs or be inaugural, being therefore one of the first features indicating the existence of an underlying immune defect. The aim of this review is to describe the orofacial features associated with the different PIDs of innate immunity based on the new 2019 classification from the International Union of Immunological Societies (IUIS) expert committee. This review highlights the important role played by the dentist, in close collaboration with the multidisciplinary medical team, in the management and the diagnostic of these conditions.

Management of a Patient With Congenital Biallelic CSF3R Mutation With GM-CSF

Severe Congenital Neutropenia (SCN) is a rare inherited disease characterized by an absolute neutrophil count (ANC) lower than 500/μL. Genetic heterogeneity and biallelic CSF3R mutation has rarely been identified as an underlying genetic defect in SCN. The majority of SCN patients respond to granulocyte colony stimulating factor treatment; however, in patients with inherited CSF3R mutation, ANC cannot generally be increased with granulocyte colony stimulating factor treatment. In such cases, granulocyte macrophage colony stimulating factor presents as an effective treatment option. Herein, we report a case of a 5-year-old SCN girl with homozygous c610-611 del ins AG (p.Q204R) mutation in the CSF3R gene, who was successfully treated with granulocyte macrophage colony stimulating factor.

Novel ELANE Gene Mutation in a Newborn with Severe Congenital Neutropenia: Case Report and Literature Review

Severe neutropenia is defined as an absolute neutrophil count (ANC) of less than 0.5 × 10 ⁹ /L. Severe congenital neutropenia (SCN) is an inborn disorder with maturation arrest of granulocytes due to various genetic abnormalities, which may lead to immunodeficiency. Among several associated genetic mutations, the variants or heterozygous mutations of the ELANE gene coding neutrophil elastase comprise approximately 50% of the genetic causes of SCN. We present a newborn (male) with severe neutropenia due to a novel ELANE gene mutation. The newborn was born at 38 ^6/7 weeks gestation to a 25-year-old mother with hypertension and morbid obesity. Pregnancy and delivery were uncomplicated but the baby obtained a complete blood count (CBC) on day of life 2 for a work up of hyperbilirubinemia. He was noted to initially have an ANC of 0.2 × 10 ⁹ /L and 0 on subsequent blood counts. A bone marrow biopsy showed a left shift and consistent with myeloid maturation arrest. In direct DNA sequencing analysis, we found an ELANE gene mutation (Val119Glu, V119E), which may be a new gene mutation to cause SCN. The diagnosis of SCN in newborns is usually based on neutropenia identified on a routine CBC. Sufficient awareness and high suspicion of this rare disease can prevent missed or delayed diagnosis of SCN. Our analysis also suggests a new pathological mutation in the ELANE gene and supports the important role of molecular testing in SCN.

Next-Generation Sequencing Reveals A JAGN1 Mutation in a Syndromic Child With Intermittent Neutropenia

BACKGROUND

Jagunal homolog 1 (JAGN1) gene was identified as a novel responsible for severe congenital neutropenia. The protein encoded by this gene is required for neutrophil differentiation, survival and function in microbial activity. JAGN1-deficient human neutrophils are characterized by alterations in trafficking within the endoplasmic reticulum and golgi compartments because of ultrastructural defects in endoplasmic reticulum and susceptibility to apoptosis.

OBSERVATIONS

We report a patient exhibiting an intermittent neutropenia, for which a next-generation sequencing revealed a homozygous mutation in the JAGN1 gene.

CONCLUSIONS

The patient extends the clinical variability associated to JAGN1 mutations, and this case highlights the importance of genetic investigations in patients with suspected neutropenia.

Human dendritic cell immunodeficiencies

The critical functions of dendritic cells (DCs) in immunity and tolerance have been demonstrated in many animal models but their non-redundant roles in humans are more difficult to probe. Human primary immunodeficiency (PID), resulting from single gene mutations, may result in DC deficiency or dysfunction. This relatively recent recognition illuminates the in vivo role of human DCs and the pathophysiology of the associated clinical syndromes. In this review, the development and function of DCs as established in murine models and human in vitro systems, discussed. This forms the basis of predicting the effects of DC deficiency in vivo and understanding the consequences of specific mutations on DC development and function. DC deficiency syndromes are associated with heterozygous GATA2 mutation, bi-allelic and heterozygous IRF8 mutation and heterozygous IKZF1 mutation. The intricate involvement of DCs in the balance between immunity and tolerance is leading to increased recognition of their involvement in a number of other immunodeficiencies and autoimmune conditions. Owing to the precise control of transcription factor gene expression by super-enhancer elements, phenotypic anomalies are relatively commonly caused by heterozygous mutations.

Periodontal and other oral manifestations of immunodeficiency diseases

The list of immunodeficiency diseases grows each year as novel disorders are discovered, classified, and sometimes reclassified due to our ever-increasing knowledge of immune system function. Although the number of patients with secondary immunodeficiencies (SIDs) greatly exceeds those with primary immunodeficiencies (PIDs), the prevalence of both appears to be on the rise probably because of scientific breakthroughs that facilitate earlier and more accurate diagnosis. Primary immunodeficiencies in adults are not as rare as once thought. Globally, the main causes of secondary immunodeficiency are HIV infection and nutritional insufficiencies. Persons with acquired immune disorders such as AIDS caused by the human immunodeficiency virus (HIV) are now living long and fulfilling lives as a result of highly active antiretroviral therapy (HAART). Irrespective of whether the patient's immune-deficient state is a consequence of a genetic defect or is secondary in nature, dental and medical practitioners must be aware of the constant potential for infections and/or expressions of autoimmunity in these individuals. The purpose of this review was to study the most common conditions resulting from primary and secondary immunodeficiency states, how they are classified, and the detrimental manifestations of these disorders on the periodontal and oral tissues.

Neutrophil Evolution and Their Diseases in Humans

Granulocytes have been preserved and have evolved across species, developing into cells that provide one of the first lines of host defense against pathogens. In humans, neutrophils are involved in early recognition and killing of infectious pathogens. Disruption in neutrophil production, emigration, chemotaxis, and function cause a spectrum of primary immune defects characterized by host susceptibility to invasive infections.

Monocyte, Macrophage, and Dendritic Cell Development: the Human Perspective

The maintenance of monocytes, macrophages, and dendritic cells (DCs) involves manifold pathways of ontogeny and homeostasis that have been the subject of intense study in recent years. The concept of a peripheral mononuclear phagocyte system continually renewed by blood-borne monocytes has been modified to include specialized DC pathways of development that do not involve monocytes, and longevity through self-renewal of tissue macrophages. The study of development remains difficult owing to the plasticity of phenotypes and misconceptions about the fundamental structure of hematopoiesis. However, greater clarity has been achieved in distinguishing inflammatory monocyte-derived DCs from DCs arising in the steady state, and new concepts of conjoined lymphomyeloid hematopoiesis more easily accommodate the shared lymphoid and myeloid phenotypes of some DCs. Cross-species comparisons have also yielded coherent systems of nomenclature for all mammalian monocytes, macrophages, and DCs. Finally, the clear relationships between ontogeny and functional specialization offer information about the regulation of immune responses and provide new tools for the therapeutic manipulation of myeloid mononuclear cells in medicine.

Dendritic cell analysis in primary immunodeficiency

Purpose of review

Dendritic cells are specialized antigen-presenting cells which link innate and adaptive immunity, through recognition and presentation of antigen to T cells. Although the importance of dendritic cells has been demonstrated in many animal models, their contribution to human immunity remains relatively unexplored in vivo.

Given their central role in infection, autoimmunity, and malignancy, dendritic cell deficiency or dysfunction would be expected to have clinical consequences.

Recent findings

Human dendritic cell deficiency disorders, related to GATA binding protein 2 (GATA2) and interferon regulatory factor 8 (IRF8) mutations, have highlighted the importance of dendritic cells and monocytes in primary immunodeficiency diseases and begun to shed light on their nonredundant roles in host defense and immune regulation in vivo. The contribution of dendritic cell and monocyte dysfunction to the pathogenesis of primary immunodeficiency disease phenotypes is becoming increasingly apparent. However, dendritic cell analysis is not yet a routine part of primary immunodeficiency disease workup.

Summary

Widespread uptake of dendritic cell/monocyte screening in clinical practice will facilitate the discovery of novel dendritic cell and monocyte disorders as well as advancing our understanding of human dendritic cell biology in health and disease.

Germline Genetic Predisposition to Hematologic Malignancy

Development of hematologic malignancies is driven by mutations that may be somatic or germline. Availability of next-generation DNA sequencing technologies has facilitated the development of individualized diagnostic evaluations and tailored treatment strategies. Until now, such personalized medical approaches have largely centered on prognostic stratification and treatment strategies informed by acquired somatic mutations. The role of germline mutations in children and adults with hematologic malignancies was previously underappreciated. Diagnosis of an inherited predisposition to hematologic malignancy informs choice of therapy, risk of treatment-related complications, donor selection for hematopoietic stem cell transplantation, evaluation of comorbidities, and surveillance strategies to improve clinical outcomes. The recognition that patients with inherited hematologic malignancy syndromes may present without classic clinical stigmata or suspicious family history has led to increased reliance on genetic testing, which, in turn, has raised new diagnostic challenges. Genomic testing is a rapidly evolving field with an increasing number of choices for testing for the practicing clinician to navigate. This review will discuss general approaches to diagnosis and management of patients with germline predisposition to hematology malignancies and will consider applications and limitations of genomic testing in clinical practice.

Neonatal manifestations of inherited bone marrow failure syndromes

The inherited bone marrow failure syndromes (IBMFS) are a rare yet clinically important cause of neonatal hematological and non-hematological manifestations. Many of these syndromes, such as Fanconi anemia, dyskeratosis congenita and Diamond-Blackfan anemia, confer risks of multiple medical complications later in life, including an increased risk of cancer. Some IBMFS may present with cytopenias in the neonatal period whereas others may present only with congenital physical abnormalities and progress to pancytopenia later in life. A thorough family history and detailed physical examination are integral to the work-up of any neonate in whom there is a high index of suspicion for an IBMFS. Correct detection and diagnosis of these disorders is important for appropriate long-term medical surveillance and counseling not only for the patient but also for appropriate genetic counselling of their families regarding recurrence risks in future children and generations.

Understanding chronic neutropenia: life is short

The pathophysiological mechanisms underlying chronic neutropenia are extensive, varying from haematopoietic stem cell disorders resulting in defective neutrophil production, to accelerated apoptosis of neutrophil progenitors or circulating mature neutrophils. While the knowledge concerning genetic defects associated with congenital neutropenia or bone marrow failure is increasing rapidly, the functional role and consequences of these genetic alterations is often not well understood. In addition, there is a large group of diseases, including primary immunodeficiencies and metabolic diseases, in which chronic neutropenia is one of the symptoms, while there is no clear bone marrow pathology or haematopoietic stem cell dysfunction. Altogether, these disease entities illustrate the complexity of normal neutrophil development, the functional role of the (bone marrow) microenvironment and the increased propensity to undergo apoptosis, which is typical for neutrophils. The large variety of disorders associated with chronic neutropenia makes classification almost impossible and possibly not desirable, based on the clinical phenotypes. However, a better understanding of the regulation of normal myeloid differentiation and neutrophil development is of great importance in the diagnostic evaluation of unexplained chronic neutropenia. In this review we propose insights in the pathophysiology of chronic neutropenia in the context of the functional role of key players during normal neutrophil development, neutrophil release and neutrophil survival.

Chronic neutrophilic leukemia: novel mutations and their impact on clinical practice

PURPOSE OF REVIEW

Chronic neutrophilic leukemia (CNL) is a rare BCR-ABL1-negative myeloid malignancy that is characterized by mature granulocytosis without dysgranulopoiesis. Differential diagnosis of CNL includes reactive or secondary granulocytosis and other myeloid neoplasms, such as atypical chronic myeloid leukemia (aCML) and chronic myelomonocytic leukemia (CMML). Herein, we focus on recently described mutations in CNL and their impact on diagnosis, prognosis and treatment.

RECENT FINDINGS

In 2013, membrane-proximal CSF3R mutations, most frequently CSF3RT618I, were described in CNL and aCML. Subsequent studies confirmed the presence of such mutations in nearly all patients with CNL but not in aCML. Furthermore, the majority of the patients with CSF3R-mutated CNL also expressed other mutations, such as SETBP1 and ASXL1, which might be prognostically detrimental. Laboratory studies revealed that CSF3RT618I induced JAK inhibitor-sensitive activation of JAK-STAT and CNL-like disease in mice. Case reports have indicated palliative but not disease-modifying activity of JAK inhibitor therapy in CSF3R-mutated CNL.

SUMMARY

CNL is now a morphologically and molecularly defined myeloid malignancy, and no longer a diagnosis of exclusion. The identification of CNL-specific molecular markers provides a much needed pathogenetic insight and also offers the opportunity to revise current diagnostic criteria and identify prognostic biomarkers and potential drug targets.

Regulation of Neutrophil Serine Proteases by Intracellular Serpins

Neutrophil granules contain serine proteases that are central components of the antimicrobial weapons of the innate immune system. Neutrophil proteases also contribute to the amplification and resolution of inflammatory responses through defined proteolytic cleavage of mediators, cell surface receptors, and extracellular matrix proteins. In the blood and at mucosal surfaces, neutrophil serine proteases are regulated by serpins found in plasma and by non-serpin secreted inhibitors. Distinct mechanisms leading to neutrophil cell death have been described for the granule serine proteases, neutrophil elastase, cathepsin G, and proteinase-3. Granule leakage in neutrophils triggers death pathways mediated by cathepsin G and proteinase-3, and both proteases are tightly regulated by their inhibitor SERPINB1 in a cell intrinsic manner. Although stored in the same types of granules, neutrophil elastase does not significantly contribute to cell death following intracellular release from granules into the cytoplasm. However, heterozygous mutations in ELANE, the gene encoding elastase, are the cause of severe congenital neutropenia, a life-threatening condition characterized by the death of neutrophils at an early precursor stage in the bone marrow. This chapter focuses on recent work exploring the biology of clade B intracellular serpins that inhibit neutrophil serine proteases and their functions in neutrophil homeostasis and serine protease control at sites of inflammation.

The antimicrobial propeptide hCAP-18 plasma levels in neutropenia of various aetiologies: a prospective study

The underlying cause of neutropenia may be difficult to determine due to similar clinical presentation in many neutropenic conditions. The neutrophil protein hCAP-18 (pro-LL-37) is a major component of neutrophil secondary granules and in this prospective study we assessed the use of hCAP-18 levels in blood plasma for differential diagnosis of neutropenic patients (n = 133) of various aetiologies. Plasma levels of hCAP-18 were determined using immunoblot and ELISA. Patients with severe congenital neutropenia (n = 23) presented with the lowest levels of plasma hCAP-18 and differential diagnostic accuracy revealed high sensitivity (100%) and specificity (98.8%) for hCAP-18 ELISA. The correlation coefficient of the hCAP-18 ELISA versus immunoblotting was (R = 0.831) and that of the peptide LL-37 ELISA versus immunoblotting was (R = 0.405) (P < 0.001). Plasma hCAP-18 levels thus displayed high diagnostic value in differential diagnosis of chronic neutropenia. Neutropenic patients with Shwachman-Diamond syndrome, Barth syndrome, Cohen syndrome, acute myeloid leukaemia and specific granule deficiency presented with reduced plasma hCAP-18 levels as well. The blood plasma level of hCAP-18 was thus low in conditions in which the neutrophil antibacterial propeptide hCAP-18 is deficient, i.e. severe congenital neutropenia and neutrophil-specific granule deficiency, and in conditions in which bone marrow myelopoiesis is negatively affected.

Genetic analysis and clinical picture of severe congenital neutropenia in Israel

BACKGROUND

The relative frequency of mutated genes among patients with severe congenital neutropenia (SCN) may differ between various ethnic groups. To date, few population-based genetic studies have been reported. This study describes the genetic analysis of 32 Israeli patients with SCN.

PROCEDURES

Clinical data were retrieved from the prospective Israeli Inherited Bone Marrow Failure Registry. Recruitment included living and deceased patients who were diagnosed between 1982 and 2012, for whom molecular diagnosis was performed. ELANE, HAX1 and G6PC3 genes were sequenced in all patients, and GFI-1 and WAS genes were sequenced if other genes were wildtype.

RESULTS

Eleven patients (34%) had heterozygous mutations in ELANE (10 kindreds), eight (25%) had homozygous mutations in G6PC3 (5 kindreds) and 13 (41%) had no detected mutations. No patients had mutations in HAX1 or WAS. Four of the eight patients with G6PC3 mutations had congenital anomalies. The probability of survival for all patients was 50% at age of 18. Deaths were mainly due to sepsis (5 patients, 4/5 not responding to G-CSF, none with G6PC3 mutation). Two patients developed acute myelogenous leukemia (AML) and one myelodysplastic syndrome (MDS), none with G6PC3 mutation.

CONCLUSIONS

We found a unique pattern of SCN mutations in Israel with homozygous G6PC3 mutations in eight (25%) patients, the highest frequency described so far. HAX1 mutations, reported mainly in Sweden and Iran, were absent. Patients with G6PC3 mutations had congenital anomalies, appeared to have a better response to G-CSF, and so far have not developed AML or MDS.

Severe congenital neutropenia due to G6PC3 deficiency: early and delayed phenotype in two patients with two novel mutations

Severe Congenital Neutropenia type 4 (SCN4, OMIM 612541) is a rare autosomal recessive disease due to mutations in the G6PC3 gene. The phenotype comprises neutropenia of variable severity and other anomalies including congenital heart defects, prominent superficial veins, uro-genital anomalies, facial dysmorphism, growth and developmental delay and intermittent thrombocytopenia. In some patients, SCN represents the only manifestation of the disease. Variable findings have been reported at bone marrow examination ranging from a maturation arrest at the myelocyte/promyelocyte stage (either in a hypocellular or hypercellular context) to myelokathexis. Here we report two patients harbouring two novel mutations in the G6PC3 gene, including the first Italian patient even described. Both the patients share profound neutropenia with severe infections early in life; in one case non-hematopoietic stigmata of the syndrome, including evident facial dysmorphism and vascular anomalies, appeared gradually over time, prominently in the second decade. Therefore, G6PC3 defects should be considered in any case of congenital, unexplained neutropenia regardless of the clinical phenotype. Both patients are on G-CSF treatment with no evidence of malignant evolution. Even if G6PC3 deficiency seems not to have a propensity towards malignancy, a careful evaluation is warranted.

Autoimmune and other cytopenias in primary immunodeficiencies: pathomechanisms, novel differential diagnoses, and treatment

Autoimmunity and immune dysregulation may lead to cytopenia and represent key features of many primary immunodeficiencies (PIDs). Especially when cytopenia is the initial symptom of a PID, the order and depth of diagnostic steps have to be performed in accordance with both an immunologic and a hematologic approach and will help exclude disorders such as systemic lupus erythematosus, common variable immunodeficiency, and autoimmune lymphoproliferative syndromes, hemophagocytic disorders, lymphoproliferative diseases, and novel differential diagnoses such as MonoMac syndrome (GATA2 deficiency), CD27 deficiency, lipopolysaccharide-responsive beige-like anchor (LRBA) deficiency, activated PI3KD syndrome (APDS), X-linked immunodeficiency with magnesium defect (MAGT1 deficiency), and others. Immunosuppressive treatment often needs to be initiated urgently, which impedes further relevant immunologic laboratory analyses aimed at defining the underlying PID. Awareness of potentially involved disease spectra ranging from hematologic to rheumatologic and immunologic disorders is crucial for identifying a certain proportion of PID phenotypes and genotypes among descriptive diagnoses such as autoimmune hemolytic anemia, chronic immune thrombocytopenia, Evans syndrome, severe aplastic anemia/refractory cytopenia, and others. A synopsis of pathomechanisms, novel differential diagnoses, and advances in treatment options for cytopenias in PID is provided to facilitate multidisciplinary management and to bridge different approaches.

Diagnostic assays for chronic granulomatous disease and other neutrophil disorders

Inasmuch as neutrophils are the primary cellular defense against bacterial and fungal infections, disorders that affect these white cells typically predispose individuals to severe and recurrent infections. Therefore, diagnosis of such disorders is an important first step in directing long-term treatment/care for the patient. Herein, we describe methods to identify chronic granulomatous disease, leukocyte adhesion deficiency, and neutropenia. The assays are relatively simple to perform and cost effective and can be performed with equipment available in most laboratories.

A novel G6PC3 gene mutation in a patient with severe congenital neutropenia

Glucose-6-phosphatase catalytic subunit 3 (G6PC3) deficiency is a newly described syndromic type of severe congenital neutropenia, associated with multiple organ abnormalities including facial, cardiac, and urogenital abnormalities, and increased visibility of superficial veins. The molecular pathophysiology of G6PC3 deficiency is associated with the disturbed glucose homeostasis, increased endoplasmic reticulum stress, and apoptosis in neutrophils. We report a new case of G6PC3 deficiency caused by a novel homozygous G6PC3 gene mutation (p.Leu154Pro). Most remarkable is that the chronic neutropenia that originated from this novel G6PC3 genetic defect is also accompanied by some other unusual manifestations in this patient: myelokathexis and hypercholesterolemia.

Coexistence of sickle cell disease and severe congenital neutropenia: first impressions can be deceiving

We report an Omani family in whom the propositus had a rare coexistence of sickle cell disease and severe congenital neutropenia associated with a mutation in ELANE. In contrast to his siblings with sickle cell disease, the severity of HbSS-associated complications such as painful crises and acute chest syndrome was significantly reduced. His course of the disease had markedly worsened after initiating G-CSF therapy. These clinical observations suggest that neutropenia may ameliorate inflammatory responses and thus display a modulating factor with respect to the clinical course of sickle cell disease.

Glycosylation of mouse and human immune cells: insights emerging from N-glycomics analyses

N-glycans are key players mediating cell–cell communication in the immune system, interacting with glycan-binding proteins. In the present article, we discuss key themes that are emerging from the structural analysis of complex-type N-linked glycans from human and murine immune cell lines, employing high-sensitivity MALDI (matrix-assisted laser desorption ionization)–TOF (time-of-flight) MS technology. Particular focus is given to terminal epitopes, the abundance of multiply branched N-glycans and how glycosylation can affect human health in diseases such as congenital neutropenia and glycogen storage disease.

Human dendritic cell deficiency: the missing ID?

Animal models and human in vitro systems indicate that dendritic cells (DCs) have a crucial role in priming naive T cells, but just how important are they in the intact human? Recent descriptions of human DC deficiency have begun to shed light on this question and to illuminate other puzzles of human DC biology, including their haematopoietic origin, developmental regulation and homeostatic equilibrium with other leukocytes. In this Review, we explore the recently described DC deficiency syndromes, discussing what these have taught us with regard to DC function in humans and the important issues that remain unsolved.