Neutropenia in general is defined as a blood neutrophil count of less than 1.5 × 109/L, in severe neutropenia counts drop to less than 0.5 × 109/L, but the definition of neutropenia varies according to the patient's ethnic origin and age. For Caucasian adults, the absolute neutrophil count (ANC) threshold of 1.8 × 109/L is adopted for the definition of neutropenia according to the World Health Organization (see Fioredda etal. (1)). It can be inherited or acquired, and it is an uncommon haematological finding in adult outpatient clinics. Neutropenia can result from decreased production of neutrophil precursors in the bone marrow, as in the case of severe congenital neutropenia, or from increased utilization of neutrophils in some bacterial infections, or accelerated destruction as is the case with drug-induced neutropenia, viral infections and autoimmune neutropenia. Severe chronic neutropenia increases susceptibility to bacterial or fungal infections. Treating severe chronic neutropenia patients with granulocyte colony-stimulating factor (G-CSF) can increase neutrophil counts for most types of neutropenia. This article will provide guidance on diagnosing and managing severe chronic neutropenia in adult patients and provides a transition programme from adolescence to adulthood.

We report a mouse model of severe congenital neutropenia due to VPS45 missense mutations. It represents the first animal model of human neutropenia due to a defect in intracellular trafficking.

Mutations in the neutrophil elastase gene (ELANE) have classically been established as the primary genetic etiology of severe congenital neutropenia (SCN) and cyclic neutropenia (CyN), characterized by early-stage granulocytic maturation arrest and a predisposition to life-threatening infections. However, recent high-throughput transcriptomic, multi-omics, and functional studies have unveiled a paradigm-shifting, multidimensional role for neutrophil elastase (NE) that extends far beyond the confines of bone marrow failure. As a highly active serine protease, NE has emerged as a central hub in regulating recently discovered forms of regulated cell death (RCD), including pyroptosis, ferroptosis, and NETosis, and orchestrating the tumor immune microenvironment (TIME). Within the bone marrow, mutant NE triggers intense proteotoxic stress, reactive oxygen species (ROS) accumulation, and a unique proapoptotic "aggrephagy" (the selective autophagic degradation of misfolded protein aggregates), driving granulocyte colony-stimulating factor (G-CSF) resistance and clonal evolution toward acute myeloid leukemia (AML). Extracellularly, NE released via neutrophil extracellular traps (NETs) acts as a fascinating double-edged sword: it possesses the intrinsic capability to selectively eradicate genetically diverse cancer cells by cleaving the CD95 death domain and interacting with histone H1 isoforms, yet it concomitantly mediates immunosuppression, chemoresistance, and systemic inflammatory response syndrome (SIRS) in sepsis by reprogramming macrophage polarization. This review systematically synthesizes the intricate molecular mechanisms of NE, emphasizing the profound crosstalk between hematopoietic failure, inflammatory cell death pathways, and tumor immunology. Furthermore, this review highlights the translational potential of these discoveries, exploring cutting-edge therapeutic strategies, including CRISPR/Cas9-based precise base editing, dual-nickase promoter targeting, and selective allosteric small-molecule inhibitors, ultimately aiming to bridge the critical gaps from bench to bedside.

The central importance of neutrophils for human health is clearly demonstrated by the clinical presentation of patients with severe congenital neutropenia (CN) and cyclic neutropenia (CyN). The majority of patients with CN with neutropenia as their only symptom do not survive the first year of life unless they are treated with recombinant human cytokine granulocyte colony-stimulating factor (rhG-CSF) or undergo allogeneic bone marrow transplantation. Understanding the processes of defective granulopoiesis downstream of CN-associated gene mutations sheds light on the mechanisms that regulate granulopoiesis and granulocyte functions. Furthermore, given that CN is a preleukemia syndrome, studying CN can help to define the role of defective granulopoiesis and deregulated neutrophil functions in leukemogenesis. The development of advanced experimental models of CN and CyN overcomes the limitations of insufficient patient material for research, leading to breakthroughs in the understanding of their pathogenesis and the development of new potential therapies.

Congenital neutropenia refers to a group of rare inherited disorders in which neutrophil development or release is disrupted, predisposing affected children to frequent infections. Among the genes involved, CXCR2 loss-of-function variants have recently been recognized as a distinct cause of the disease. Here, we report a 12-month-old Chinese boy, who presented with repeated febrile respiratory illnesses and intermittent neutropenia since the age of 10 months. During each episode of the child’s viral infection, absolute neutrophil counts ranged between 0.13 and 0.44 ×10 9 /L, while hemoglobin and platelet values remained within the expected range. Lymphocyte subsets and immunoglobulin levels were normal. Whole-exome sequencing revealed two novel CXCR2 variants: a frameshift mutation (c.665delT, p.Val222GlyfsTer4) from his mother and a missense mutation (c.748A>C, p.Met250Leu) from his father. He required intermittent courses of granulocyte colony-stimulating factor and broad-spectrum antibiotics during neutropenic fever episodes. This case expands the mutational and phenotypic spectrum of CXCR2 -related congenital neutropenia and highlights the value of genetic testing for infants with unexplained chronic neutropenia and recurrent infections.

The multicellular metazoan lineage acquired a novel chaperone in the mitochondrial intermembrane space, the AAA+ disaggregase and refoldase CLPB. Although it is not known how they function together, CLPB and the intrinsically disordered IMS protein HAX1 interact and share disease and cellular phenotypes; loss of function in either gene causes severe congenital neutropenia as well as neuropathology and causes many proteins in the IMS and its bounding membranes to become insoluble. We sought to determine how HAX1 functions with CLPB. Through biochemical reconstitution, we find that HAX1 is a stimulatory cofactor of CLPB. HAX1 promotes oligomerization of CLPB into an active disaggregase and stimulates the ATPase and refoldase activities of the oligomeric complex. A short peptide within HAX1 is necessary for direct interaction with the ankyrin domain of CLPB, but stimulation of CLPB activity requires additional elements of HAX1. Characterization of CLPB and CLPB-HAX1 oligomers indicates that HAX1 shifts the predominant oligomeric state of CLPB from a dodecamer to a hexamer elaborated 1:1 with HAX1, suggesting that this smaller oligomer is important during the cycle of CLPB function with clients.

Severe congenital neutropenia (SCN) is a rare hematological disorder characterized by a marked reduction in circulating neutrophils and recurrent infections. This study aimed to evaluate bone metabolism in patients with SCN via biochemical and bone mineral density (BMD) measurements. This study included 76 patients who were diagnosed with SCN at six tertiary immunology centers. Demographic, clinical, laboratory, and BMD findings were retrospectively analyzed and measured via dual-energy X-ray absorptiometry (DXA). The study included 76 patients, 39 (51.3%) females and 37 (48.7%) males. The mean age was 206.9 ± 105.1 months, with a median age at diagnosis of 18.5 months (range: 1-264) and a follow-up period of 120 months (range: 2-324). Parental consanguinity was present in 57 patients (75%). Among patients evaluated by DXA, 30 (39.5%) had low BMD, with a mean BMD score of 0.63 ± 0.20 and a Z-score of -2.88 ± 0.90. Osteoporosis was detected in 11 adult patients (29.7%). The most common genetic mutations were HAX1 in 46 patients (60.5%) and ELANE in 15 patients (19.7%). No significant difference in BMD was observed between patients with HAX1 and ELANE mutations (p = 0.60). Granulocyte colony-stimulating factor (G-CSF) was administered to 73 patients. The median G-CSF dose was 5 (2-12) µg/kg/day in the normal BMD group and 5 (2-10) µg/kg/day in the low BMD group. No significant relationship was found between the duration or dose of G-CSF and BMD (p = 0.76, p = 0.38). Additionally, 13 patients received vitamin D, four received calcium, and one was treated with calcitonin and alendronate. Our findings indicate that patients with SCN have a high prevalence of bone mineral loss. The underlying pathophysiology and potential effects of recombinant G-CSF treatment on increased bone mineral loss remain controversial and warrant further investigation.

Molecular mechanisms underlying congenital neutropenia in patients with HAX1 deficiency are not clear at the moment. HAX1 deficiency was shown to result in the arrest of neutrophil differentiation. Our studies of the effect of HAX1 deficiency on the proteomic and metabolic profiles of promyelocytic cells have led to the conclusion, supported by specific tests, that fatty acid metabolism is affected in HAX1 KO cells. The lipid droplet content is increased in HAX1 KO cells, pointing to the accumulation of fatty acids that are not metabolized. Studies of autophagosome function in HAX1 WT and KO cells revealed that lipid droplet autophagy is defective at the stage of fusion with the lysosome. Autophagy-dependent generation of free fatty acids is critical for neutrophil differentiation, so HAX1 deficiency that affects normal autophagy of lipids in promyeloblasts should explain differentiation arrest. Moreover, we have demonstrated that HAX1-deficient cells are also compromised in fatty acid uptake.

Septins are a conserved family of hematopoietic cytoskeletal regulators. We report two full-term male siblings with a stop-loss variant in the X-linked SEPTIN6 gene who tested positive on SCID newborn screening and presented with myeloid tetraploidy, congenital neutropenia, absent circulating B cells, and variable T cell lymphopenia despite a normal percentage of naive T cells. In the proband, neutropenia was unresponsive to G-CSF with undetectable antineutrophil antibody. Both siblings had hypersegmented myeloid forms and tetraploidy with subsequent development of trisomy 8. One sibling had monosomy 7. Mature and progenitor B cells were markedly decreased to absent; rare plasma cells were present. Mature myeloid forms and plasma cells accumulated in the marrow leading to peripheral neutropenia and B cell lymphopenia. Matched sibling myeloablative HSCT resulted in full disease correction and minimal-to-no GVHD. In xenograft studies, altered SEPTIN6 function led to reduced early lymphoid progenitor cells, demonstrating that SEPTIN6 plays a critical role in lymphocyte development, representing a new inborn error of immunity.

Severe congenital neutropenia (SCN) is a heterogeneous hematopoietic disorder characterized by impaired granulocyte maturation and increased susceptibility to infections. Over 25 genes have been linked to SCN, yet the molecular pathogenesis remains unknown in 30%-50% of cases. This study aimed to expand the understanding of SEC61A1 variant-mediated diseases. Clinical data were collected from the patient. Whole-exome sequencing was performed, followed by Sanger sequencing for familial validation. Bioinformatics, conservation, and protein structural analyses were conducted to evaluate candidate variants. We report an 11-year-old boy with decreased neutrophils and lymphocytes, and elevated proportions of monocytes and eosinophils. Bone marrow showed granulocytic hyperplasia with maturation arrest and nuclear abnormalities. Flow cytometric analysis of bone marrow cells is indicative of aberrant myeloid antigen differentiation and impaired granulocytic maturation. A novel de novo pathogenic SEC61A1 variant (c.1135 T > C; p.Trp379Arg) was identified. Structural analysis suggested that this variant may disrupt protein conformational stability. The SEC61A1 c.1135 T > C (p.Trp379Arg) variant is considered likely pathogenic. This is the second reported SEC61A1 variant associated with SCN11, expanding the genetic and phenotypic spectrum of SCN.

CLPB-related mitochondrial disease causes congenital neutropenia, developmental delay/intellectual disability, progressive brain atrophy, movement disorders, cataracts, and 3-methylglutaconic aciduria. Both monoallelic and biallelic forms exist. This retrospective cohort study compared clinical outcomes and genotype-structure-phenotype correlations across zygosity groups. Sixty-three individuals (41 biallelic, 22 monoallelic; 6 unpublished) with disease-causing CLPB variants were identified via literature review and a multicenter survey. In silico modeling assessed structural impact. A modified CLPB Disease Burden Index (DBI) quantified severity. Median age at last follow-up was 4.0years (IQR: 0.25-12.6) in biallelic and 12.0years (IQR: 5.3-21.0) in monoallelic cases. Death occurred in 66% of biallelic and 23% of monoallelic individuals, with earlier median age at death in biallelic cases (6months vs 2.4years). Biallelic cases had significantly higher DBI scores and poorer survival (4-year survival: 50% vs 82%). Stop/stop genotypes were associated with greater disease burden than missense combinations. Structural predictions-particularly variants causing nonsense-mediated decay or ankyrin domain disruption-were stronger survival predictors than zygosity or age of onset. Early-onset disease (<12months) correlated with more severe progression. Later onset often resulted in milder phenotypes. Hematologic and neurologic features overlapped across zygosity; cataracts and dystonia were more common in biallelic cases. Milestone attainment was poor, with <50% walking or speaking, and only 10-20% doing so on time. Four monoallelic patients received hematopoietic stem cell transplants with mixed outcomes. Granulocyte colony-stimulating factor was associated with improved survival. This is the largest cohort study to date comparing biallelic and monoallelic CLPB deficiency. Structural variant impact-particularly ankyrin domain disruption-emerged as a key prognostic factor.

Congenital neutropenia, particularly ELANE-associated forms, is associated with recurrent oral infections and aggressive periodontitis. While ELANE deficiency compromises oral health, its relationship to plaque biofilm ecology and metabolic function remains unclear. The oral microbiome-metabolome interplay in this condition remains largely uncharacterized globally. Here, we address this gap by characterizing the dental plaque metagenome and inferred metabolic pathways in a defined cohort of Thai neutropenia patients. In this exploratory study, we sequenced dental plaque samples from a defined cohort of nine individuals: three patients with severe congenital neutropenia or cyclic neutropenia (CyN) with confirmed ELANE variants, and six from age- and gender-matched healthy controls. Shotgun metagenomics was used for genomic analysis, followed by comprehensive microbiota examination. Subsequently, MetaCyc, a curated database, was used for in silico analysis and comparisons of the predicted functional pathways between the test and control plaque biofilms. The principal coordinate analysis plot and heat map revealed distinct segregation of microbial profiles between the patients and control groups. A significant variation in the proportions of the five core phyla was noted in patients and controls. Two commensal species, Aggregatibacter sp oral taxon 458 and Leptotrichia sp oral taxon 212, were enriched in the controls. Conversely, four species were significantly enriched in the patients, Selenomonas flueggei, Streptococcus milleri, Kingella oralis, and Actinobaculum sp oral taxon 183; the latter being notably elevated across all patients. The MetaCyc in silico analyses suggested predicted enrichment of functional pathways associated with inflammation and oxidative stress in patients, including L-methionine biosynthesis IV, formaldehyde assimilation III, L-rhamnose degradation, and the superpathway of (R,R)-butanediol biosynthesis pathways. Our study advances the understanding of ELANE-associated periodontitis by moving beyond descriptive microbiota analysis to suggest potential associations between host immune deficiency, microbial dysbiosis, and the microbiota-associated metabolic pathway alterations. These findings provide preliminary insights into targeted periodontal care in neutropenic patients, though further validation in larger cohorts is required.

More than 30 distinct genetic entities associated with severe congenital neutropenia (SCN) have been described. SCN has a risk of clonal expansion of mutated hematopoietic cells. Jagunal homolog 1 (JAGN1) deficiency has been described as a genetic cause of SCN and is now estimated to account for approximately 10% of all SCN cases. One prevalent variant in patients with JAGN1 deficiency is NM_032492.4:c.63G>T (p.Glu21Asp). The clinical description and disease evolution study of Romanian patients with JAGN1 deficiency caused by the JAGN1 c.63G>T variant were performed together with a literature review of similar cases. The clinical characterization of six Romanian patients and nine additional patients reported in the literature with JAGN1 deficiency caused by the c.63G>T variant (40% female) revealed a wide phenotypic spectrum, including: neutropenia (all), severe infections (80%), developmental delay (13%), dental problems such as stomatitis/periodontitis (66%), and short stature (7%). No patient developed malignancy/leukemia during the follow-up period (15 ± 8.1 years). Most patients (93%) had a homozygous variant and consanguineous background, while one had compound heterozygous JAGN1 variants. The five Romanian patients carrying this homozygous variant, possibly due to a founder effect, had a relatively favorable clinical outcome, with good overall prognosis.

A previously healthy Caucasian man in his 30s presented with a 9-week history of productive cough, fever and dyspnoea, initially treated as pneumonia with transient improvement. Examination revealed coarse right-sided crepitations and finger clubbing. Laboratory testing demonstrated persistent severe neutropenia and elevated inflammatory markers, while imaging showed persistent right middle lobe consolidation. Further history revealed recurrent respiratory infections, diarrhoea and poor dentition since childhood, with medical records showing possible neutrophil migration defect. The patient received 6 weeks of broad-spectrum antibiotics and granulocyte-colony stimulating factor, resulting in resolution of consolidation and modest neutrophil recovery. Acquired causes of immunosuppression were excluded through microbiological and immunological workup. Stool testing confirmed pancreatic exocrine insufficiency. Genetic testing identified a pathogenic heterozygous signal recognition particle-54 mutation, consistent with Shwachman Diamond-like syndrome. Given the risk of leukaemic transformation, the patient was referred for haematopoietic stem cell transplantation. This case underscores the need for a multidisciplinary approach to manage rare neutropenic syndromes.

Introduction. Congenital neutropenia is a severe and potentially fatal condition putting patients at high risk for life-threatening infections. Aim: to analyze the genetic heterogeneity in severe congenital neutropenia in children treated at the federal hospital. Materials and methods. The study included 178 patients aged 0 to 18 years, with the male-to-female ratio of 1.14:1 (95 boys and 83 girls). The inclusion criteria were: persistent or recurrent neutropenia in the complete blood count, either as an isolated finding or as a feature of a syndromic disease. All the patients underwent molecular genetic testing using high-throughput next generation sequencing, Sanger sequencing or multiplex ligation-dependent probe amplification (to confirm large deletions). Results. A large variety of genetic defects associated with congenital neutropenia were identified. The majority of the patients (38% (67/178)) had Shwachman–Diamond syndrome with biallelic defects in the SBDS gene, with the combination of the c.258+2TC and с.183_184delTAinsCT variants being the most common finding in this group (identified in 75% of the cases). Severe congenital neutropenia type 1 caused by defects in the ELANE gene was found in 28% (49/178) of the patients. The variants were located in all the exons as well as in introns 3 and 4. Some of the patients (7/49) had unfavourable amino acid substitutions at GLY214 and CYS151 associated with agranulocytosis, lack of response to granulocyte colony-stimulating factor and myelodysplastic syndrome. GATA2 deficiency was diagnosed in 8% (14/178) of the patients. Genetic variants in the GATA2 gene were identified in exons 5 and 6 and intron 5, most of them being missense (43% (6/14)) or nonsense (28% (4/14)) mutations. In 1 patient, a large whole-gene deletion was confirmed. WHIM syndrome was reported in 6% (11/178) of the patients. The most common heterozygous variant in the CXCR4 gene was c.1000CT – 64% (7/11). In some rare cases described here, congenital neutropenia was caused by defects in such genes as CSF3R, GFI1, G6PC3, TAFAZZIN, VPS13B, CLPB, RAC2, LYST, RAB27A, DNAJC21, SRP54, SLC37A4, USB1 or in the recently reported COPZ1 gene. We also identified few patients with X-linked congenital neutropenia associated with activating variants in the WAS gene. Conclusion. Modern genetic technologies allow for early diagnosis, optimal treatment selection and identification of novel genes involved in congenital neutropenia. As we continue to encounter familial cases, the importance of timely genetic and prenatal/preimplantation testing cannot be overstated.

Rationale:Congenital neutropenia (CN) encompasses a group of disorders characterized by impaired neutrophil differentiation, resulting in persistently low neutrophil counts in the peripheral blood. It presents with recurrent infections and an elevated risk of leukemia. Multiple genetic mutations have been implicated in the pathogenesis of neutropenia.Patient concerns:This paper reports the case of a 3-year-2-month-old boy admitted with a 4-day history of cough and fever, accompanied by recurrent respiratory infections, neutropenia, and growth retardation. Whole-exome sequencing identified a mutation in the caseinolytic peptidase B homolog (CLPB) gene (NM_030813.6: c.1681C>T: p.R561W).Diagnoses:Although the initial genetic sequencing did not reveal mutations consistent with the clinical presentation, the child continued to experience recurrent infections. Upon reanalysis, a pathogenic CLPB-related mutation was detected, leading to the diagnosis of CN.Interventions:During hospitalization, the patient received targeted antimicrobial therapy based on the identification of the pathogen. Following the confirmed diagnosis, he also received intermittent granulocyte colony-stimulating factor therapy.Outcomes:Administration of granulocyte colony-stimulating factor successfully maintained neutrophil counts above 0.5 × 109/L and significantly reduced the frequency of respiratory tract infections.Lessons:CLPB deficiency should be considered in pediatric patients presenting with CN and concurrent neurological symptoms, as early recognition allows for the timely initiation of appropriate treatment strategies and contributes to improved clinical outcomes.

Neutrophils, the first cells to arrive at the site of inflammation, are rather short-lived cells and thus have to be constantly replenished. During neutrophil development, vesicle dynamics need to be fine-tuned and impaired vesicle trafficking has been linked to failure in neutrophil maturation. Here, we characterized the role of VPS18 as a central core component of CORVET & HOPS tethering complexes for neutrophil development. Using CRISPR/Cas9-engineered Hoxb8 cells with heterozygous mutations in Vps18, we found that VPS18 deficiency interfered with neutrophil development due to tethering complex instability. As a result, vesicle dynamics were impaired with a strong increase in LC3B-II and p62 levels, indicating autophagosome accumulation and reduced autophagic flux. With transmission electron microscopy, we verified the increase in autophagosomes and also found irregularly shaped vesicular structures in Vps18 mutants. Subsequently, Vps18 mutant neutrophil progenitors underwent premature apoptosis. We described a novel patient with a heterozygous stop-gain mutation in VPS18 suffering from neutropenia and recurrent infections. To verify our findings in the human system, we used human induced pluripotent stem cells (iPSCs). Upon differentiation into neutrophils, loss of VPS18 resulted in an almost complete absence of iPSC-derived developing neutrophils. Heterozygous VPS18 mutant and patient mutation-harboring iPSCs were characterized by strongly reduced numbers of developing neutrophils. Zebrafish larvae with heterozygous mutations in vps18 were also characterized by significantly reduced neutrophil numbers. This study shows the pivotal impact of VPS18 for adequate vesicle dynamics during neutrophil development which might be relevant in the context of vesicle trafficking during granulopoiesis and congenital neutropenia.

Individuals with neutropenia or defective neutrophil disorders exhibit significantly increased susceptibility to oral infections and dental complications compared to the general population. Despite the elevated risk profile associated with these conditions, comprehensive and standardized dental care guidelines for affected individuals remain limited. Optimal management requires a multidisciplinary approach that incorporates pre-procedural risk stratification, individualized treatment planning, and appropriate post-procedural care strategies. There is a pressing need for well-controlled clinical studies to evaluate the efficacy of prophylactic antibiotic regimens and granulocyte colony-stimulating factor in mitigating infection risks in this vulnerable population. However, the rarity and heterogeneity of neutrophil disorders pose substantial challenges to the development of evidence-based protocols. Risk assessment must be individualized, tailored to individual patient profiles, considering factors such as the degree of neutropenia, prior history of infections, and the nature of planned dental procedures. Here, we review and summarize guidelines for dental management in patients with congenital neutrophil disorders and propose the need for targeted, evidence-based clinical studies to ensure safe and effective care.

Introduction Severe congenital neutropenia type 1 (SCN1) is a rare hereditary disorder caused by a maturation arrest in granulocyte development, most frequently associated with mutations in the ELANE gene, which encodes neutrophil elastase. Case Presentation Female patient, 3 years and 5 months old, with a history of recurrent perianal infections and necrotizing fasciitis secondary to complicated appendicitis with septic shock. She required laparotomy, appendectomy, ileostomy, debridement, and vasopressor support. During hospitalization, persistent severe neutropenia, lymphopenia, and eosinophilia were identified. Bone marrow aspiration showed a maturation arrest in the myeloid lineage with absence of neutrophils. Infectious isolates included Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and rhinovirus/enterovirus. Absolute neutrophil counts remained persistently low (100–530/μL), with a response to the administration of G-CSF (granulocyte colony stimulating factor: 5 mcg/kg/dose). Genetic sequencing revealed a heterozygous nonsense mutation in ELANE (c.684C&amp;gt;G, p.Tyr228Ter). Discussion The diagnosis of SCN1 was clinically supported by severe infections, persistent neutropenia, absence of mature granulocytes in the bone marrow, and genetic confirmation. This mutation generates a premature stop codon. Other relevant variants include GFI1, HAX1, VPS45, JAGN1, CSF3R, and WAS. Conclusion SCN1 should be suspected in pediatric patients with recurrent severe infections and persistent neutropenia. Early identification and treatment with G-CSF may improve clinical outcomes and reduce infectious complications.

IN VITRO MODEL OF STAGE-SPECIFIC EVOLUTION OF CLONAL HEMATOPOIESIS IN CN TO CN/AML