WHIM Syndrome Research Articles

CXCR4 signaling determines the fate of hematopoietic multipotent progenitors by stimulating mTOR activity and mitochondrial metabolism

Both cell-intrinsic and niche-derived, cell-extrinsic cues drive the specification of hematopoietic multipotent progenitors (MPPs) in the bone marrow, which comprise multipotent MPP1 cells and lineage-restricted MPP2, MPP3, and MPP4 subsets. Patients with WHIM syndrome, a rare congenital immunodeficiency caused by mutations that prevent desensitization of the chemokine receptor CXCR4, have an excess of myeloid cells in the bone marrow. Here, we investigated the effects of increased CXCR4 signaling on the localization and fate of MPPs. Knock-in mice bearing a WHIM syndrome–associated CXCR4 mutation ( CXCR4 1013 ) phenocopied the myeloid skewing of bone marrow in patients. Whereas MPP4 cells in wild-type mice differentiated into lymphoid cells, MPP4s in CXCR4 1013 knock-in mice differentiated into myeloid cells. This myeloid rewiring of MPP4s in CXCR4 1013 knock-in mice was associated with enhanced signaling mediated by the kinase mTOR and increased oxidative phosphorylation (OXPHOS). MPP4s also localized further from arterioles in the bone marrow of knock-in mice compared with wild-type mice, suggesting that the loss of extrinsic cues from the perivascular niche may also contribute to their myeloid skewing. Chronic treatment with the CXCR4 antagonist AMD3100 or the mTOR inhibitor rapamycin restored the lymphoid potential of MPP4s in knock-in mice. Thus, CXCR4 desensitization drives the lymphoid potential of MPP4 cells by dampening the mTOR-dependent metabolic changes that promote myeloid differentiation.

Mavorixafor: A spotlight on the clinical aspects and prospects of the first USFDA-approved treatment for the primary immunodeficiency WHIM syndrome

WHIM syndrome (WHIMS) is an extremely rare, severe, and potentially fatal genetic condition that affects the immune system, leading to warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM). Effective therapy for WHIMS requires regular monitoring, medical intervention, and a collaborative approach to treatment. Due to the limited therapeutic options, addressing WHIMS is an unmet medical need. The United States Food and Drug Administration (USFDA) recently granted approval for mavorixafor as the first treatment for WHIMS. This review focuses on the pharmacological characteristics, clinical investigations, associated inventions, and prospects of mavorixafor. The literature for this article was searched on PubMed, reputable websites (USFDA and X4 Pharmaceuticals) and free patent databases like Espacenet. WHIMS is distinguished by severe neutropenia and hypogammaglobulinemia, which increases the risk of developing cancer. Mavorixafor enhances the movement of neutrophils and lymphocytes from the bone marrow (BM) to the bloodstream. Hence, it could be beneficial for managing medical illnesses characterized by a decrease in the quantity of neutrophils and lymphocytes in the bloodstream. X4 Pharmaceuticals has submitted patent applications for the utilization of mavorixafor in the treatment of diverse cancer types, inflammatory ailments, B-cell dysfunction, Waldenstrom's macroglobulinemia, and primary immunodeficiency disorders. This suggests that mavorixafor can effectively treat various disorders either alone or when used in conjunction with other medications. It will be intriguing to observe the future approvals of mavorixafor for various disorders.Keywords: Mavorixafor; WHIM syndrome; Cancer; Immunodeficiency; Patent; Prospect

Increased Susceptibility of WHIM Mice to Papillomavirus-induced Disease is Dependent upon Immune Cell Dysfunction.

Warts, Hypogammaglobulinemia, Infections, and Myelokathexis (WHIM) syndrome is a rare primary immunodeficiency disease in humans caused by a gain of function in CXCR4, mostly due to inherited heterozygous mutations in CXCR4. One major clinical symptom of WHIM patients is their high susceptibility to human papillomavirus (HPV) induced disease, such as warts. Persistent high risk HPV infections cause 5% of all human cancers, including cervical, anogenital, head and neck and some skin cancers. WHIM mice bearing the same mutation identified in WHIM patients were created to study the underlying causes for the symptoms manifest in patients suffering from the WHIM syndrome. Using murine papillomavirus (MmuPV1) as an infection model in mice for HPV-induced disease, we demonstrate that WHIM mice are more susceptible to MmuPV1-induced warts (papillomas) compared to wild type mice. Namely, the incidence of papillomas is higher in WHIM mice compared to wild type mice when mice are exposed to low doses of MmuPV1. MmuPV1 infection facilitated both myeloid and lymphoid cell mobilization in the blood of wild type mice but not in WHIM mice. Higher incidence and larger size of papillomas in WHIM mice correlated with lower abundance of infiltrating T cells within the papillomas. Finally, we demonstrate that transplantation of bone marrow from wild type mice into WHIM mice normalized the incidence and size of papillomas, consistent with the WHIM mutation in hematopoietic cells contributing to higher susceptibility of WHIM mice to MmuPV1-induced disease. Our results provide evidence that MmuPV1 infection in WHIM mice is a powerful preclinical infectious model to investigate treatment options for alleviating papillomavirus infections in WHIM syndrome.

Unexpected diagnosis of WHIM syndrome in refractory autoimmune cytopenia

AbstractWHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome is a rare primary immunodeficiency predominantly caused by heterozygous gain-of-function mutations in the C-terminus of the gene CXCR4. These CXCR4 variants display impaired receptor trafficking with persistence of the CXCR4 receptor on the surface, resulting in hyperactive downstream signaling after CXCL12 stimulation. In turn, this results in defective lymphoid differentiation, and reduced blood neutrophil and lymphocyte numbers. Here, we report a CXCR4 mutation that in 2 members of a kindred, led to life-long autoimmunity and lymphoid hypertrophy as the primary clinical manifestations of WHIM syndrome. We examine the functional effects of this mutation, and how these have affected phosphorylation, activation, and receptor internalization.

Mavorixafor: First Approval.

Mavorixafor (XOLREMDI™) is an oral, selective C-X-C chemokine receptor 4 (CXCR4) antagonist developed by X4 Pharmaceuticals that blocks the binding of C-X-C chemokine ligand 12 (also known as stromal derived factor-1) to CXCR4. In April 2024, it became the first therapy to be approved for WHIM syndrome (named by an acronym for its observed characteristics of Warts, Hypogammaglobulinaemia, Infections and Myelokathexis) in the USA, where it is indicated for use in patients aged ≥ 12years with WHIM syndrome to increase the number of circulating mature neutrophils and lymphocytes. Clinical development of mavorixafor is ongoing for chronic neutropenic disorders. This article summarizes the milestones in the development of mavorixafor leading to this first approval for use in patients aged ≥ 12 years with WHIM syndrome to increase the number of circulating mature neutrophils and lymphocytes.

Expanding CXCR4 variant landscape in WHIM syndrome: integrating clinical and functional data for variant interpretation.

Warts, Hypogammaglobulinemia, Infections, Myelokathexis (WHIM) syndrome is a rare, combined immunodeficiency disease predominantly caused by gain-of-function variants in the CXCR4 gene that typically results in truncation of the carboxyl terminus of C-X-C chemokine receptor type 4 (CXCR4) leading to impaired leukocyte egress from bone marrow to peripheral blood. Diagnosis of WHIM syndrome continues to be challenging and is often made through clinical observations and/or genetic testing. Detection of a pathogenic CXCR4 variant in an affected individual supports the diagnosis of WHIM syndrome but relies on an appropriate annotation of disease-causing variants. Understanding the genotypic-phenotypic associations in WHIM syndrome has the potential to improve time to diagnosis and guide appropriate clinical management, resulting in a true example of precision medicine. This article provides an overview of the spectrum of CXCR4 variants in WHIM syndrome and summarizes the various lines of clinical and functional evidence that can support interpretation of newly identified variants.

Plerixafor for pathogen-agnostic treatment in murine thigh infection and zebrafish sepsis.

Plerixafor is a CXCR4 antagonist approved in 2008 by the FDA for hematopoietic stem cell collection. Subsequently, plerixafor has shown promise as a potential pathogen-agnostic immunomodulator in a variety of preclinical animal models. Additionally, investigator-led studies demonstrated plerixafor prevents viral and bacterial infections in patients with WHIM syndrome, a rare immunodeficiency with aberrant CXCR4 signaling. Here, we investigated whether plerixafor could be repurposed to treat sepsis or severe wound infections, either alone or as an adjunct therapy. In a Pseudomonas aeruginosa lipopolysaccharide (LPS)-induced zebrafish sepsis model, plerixafor reduced sepsis mortality and morbidity assessed by tail edema. There was a U-shaped response curve with the greatest effect seen at 0.1 μM concentration. We used Acinetobacter baumannii infection in a neutropenic murine thigh infection model. Plerixafor did not show reduced bacterial growth at 24 h in the mouse thigh model, nor did it amplify the effects of a rifampin antibiotic therapy, in varying regimens. While plerixafor did not mitigate or treat bacterial wound infections in mice, it did reduce sepsis mortality in zebra fish. The observed mortality reduction in our LPS model of zebrafish was consistent with prior research demonstrating a mortality benefit in a murine model of sepsis. However, based on our results, plerixafor is unlikely to be successful as an adjunct therapy for wound infections. Further research is needed to better define the scope of plerixafor as a pathogen-agnostic therapy. Future directions may include the use of longer acting CXCR4 antagonists, biased CXCR4 signaling, and optimization of animal models.

A phase 3 randomized trial of mavorixafor, a CXCR4 antagonist, for WHIM syndrome

AbstractWe investigated efficacy and safety of mavorixafor, an oral CXCR4 antagonist, in participants with warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome, a rare immunodeficiency caused by CXCR4 gain-of-function variants. This randomized (1:1), double-blind, placebo-controlled, phase 3 trial enrolled participants aged ≥12 years with WHIM syndrome and absolute neutrophil count (ANC) ≤0.4 × 103/μL. Participants received once-daily mavorixafor or placebo for 52 weeks. The primary end point was time (hours) above ANC threshold ≥0.5 × 103/μL (TATANC; over 24 hours). Secondary end points included TAT absolute lymphocyte count ≥1.0 × 103/μL (TATALC; over 24 hours); absolute changes in white blood cell (WBC), ANC, and absolute lymphocyte count (ALC) from baseline; annualized infection rate; infection duration; and total infection score (combined infection number/severity). In 31 participants (mavorixafor, n = 14; placebo, n = 17), mavorixafor least squares (LS) mean TATANC was 15.0 hours and 2.8 hours for placebo (P < .001). Mavorixafor LS mean TATALC was 15.8 hours and 4.6 hours for placebo (P < .001). Annualized infection rates were 60% lower with mavorixafor vs placebo (LS mean 1.7 vs 4.2; nominal P = .007), and total infection scores were 40% lower (7.4 [95% confidence interval [CI], 1.6-13.2] vs 12.3 [95% CI, 7.2-17.3]). Treatment with mavorixafor reduced infection frequency, severity, duration, and antibiotic use. No discontinuations occurred due to treatment-emergent adverse events (TEAEs); no related serious TEAEs were observed. Overall, mavorixafor treatment demonstrated significant increases in LS mean TATANC and TATALC, reduced infection frequency, severity/duration, and was well tolerated. The trial was registered at www.clinicaltrials.gov as #NCT03995108.

7 Phase 3 Trial of an Oral CXCR4 Antagonist, Mavorixafor, for Treatment of Patients With WHIM Syndrome: Preliminary Results From Ongoing Open-Label Extension Period of Continuous Mavorixafor Treatment

7 Phase 3 Trial of an Oral CXCR4 Antagonist, Mavorixafor, for Treatment of Patients With WHIM Syndrome: Preliminary Results From Ongoing Open-Label Extension Period of Continuous Mavorixafor Treatment

194 Characterizing a unique B-cell precursor population as a potential diagnostic tool for WHIM syndrome and APDS

194 Characterizing a unique B-cell precursor population as a potential diagnostic tool for WHIM syndrome and APDS

CXCR4 WHIM syndrome is a cancer predisposition condition for virus-induced malignancies.

Warts, hypogammaglobulinaemia, infections and myelokathexissyndrome (WHIMS) is a rare combined primary immunodeficiency caused by the gain of function of the CXCR4 chemokine receptor. We present the prevalence of cancer in WHIMS patients based on data from the French Severe Chronic Neutropenia Registry and an exhaustive literature review. The median follow-up of the 14 WHIMS 'patients was 28.5 years. A central review and viral evaluation of pathological samples were organized, and we conducted a thorough literature review to identify all reports of WHIMS cases. Six French patients were diagnosed with cancer at a median age of 37.6 years. The 40-year risk of malignancy was 39% (95% confidence interval [CI]: 6%-74%). We observed two human papillomavirus (HPV)-induced vulvar carcinomas, three lymphomas (two Epstein-Barr virus [EBV]-related) and one basal cell carcinoma. Among the 155 WHIMS cases from the literature, 22 cancers were reported in 16 patients, with an overall cancer 40-year risk of 23% (95% CI: 13%-39%). Malignancies included EBV-associated lymphoproliferative disorders and HPV-positive genital and anal cancers as in the French cohort. Worldwide, nine cases of malignancy were associated with HPV and four with EBV. Immunocompromised WHIMS patients appear to be particularly susceptible to developing early malignancy, mainly HPV-induced carcinomas, followed by EBV-related lymphomas.

WHIM-синдром: обзор литературы и описание двух собственных клинических наблюдений в одной семье

WHIM syndrome (warts, hypogammaglobulinemia, infections, and myelokathexis) is a rare genetic disease associated with activating germline mutations in the gene encoding chemokine receptor CXCR4. WHIM syndrome is manifested by neutropenia, lymphopenia, infections, and degenerative changes of mature neutrophils with bone marrow myeloid hyperplasia (myelokathexis). Some patients show hypogammaglobulinemia, persistent cutaneous, genital, or elsewhere localized warts. There are also cases of congenital heart defects. The present paper extensively analyzes genetic basis, pathophysiology, clinical manifestations, and diagnosis of WHIM syndrome as well as its treatment options. The paper reports two cases in one family.

Interplay between androgen and CXCR4 chemokine signaling in myelin repair

In men, reduced levels of testosterone are associated with the prevalence and progression of multiple sclerosis (MS), a chronic and disabling demyelinating disorder. Testosterone has been shown to promote myelin repair. Here, we demonstrate that the cooperation between testosterone and CXCR4 signaling involving astrocytes is required for myelin regeneration after focal demyelination produced in the ventral mouse spinal cord by the infusion of lysolecithin. The testosterone-dependent remyelination of axons by oligodendrocytes was accompanied by an increase in astrocytes expressing CXCR4, its ligand CXCL12 and the androgen receptor (AR) within the demyelinated area. Depriving males of their testosterone or pharmacological inhibition of CXCR4, with the selective antagonist AMD3100, prevented the appearance of astrocytes expressing CXCR4, CXCL12 and AR within the demyelinated area and the concomitant recruitment of myelin forming oligodendrocytes. Conditional genetic ablation of either CXCR4 or AR in astrocytes also completely blocked the formation of new myelin by oligodendrocytes. Interestingly, the gain of function mutation in CXCR4 causing WHIM syndrome allows remyelination to take place, even in the absence of testosterone, but its potentiating effects remained observable. After testosterone deprivation or CXCR4 inhibition, the absence of astrocytes within the demyelinated area led to the incursion of Schwann cells, most likely derived from spinal nerves, and the formation of peripheral nerve type myelin. In patients with progressive MS, astrocytes expressing CXCR4 and AR surrounded myelin lesions, and their presence opposed the incursion of Schwann cells. These results highlight a mechanism of promyelinating testosterone signaling and the importance of normalizing its levels in combined myelin repair therapies.

Heterogeneous phenotype of a Chinese Familial WHIM syndrome with CXCR4V340fs gain-of-function mutation.

WHIM syndrome is a rare, autosomal dominant inborn error of immunity characterized by warts, hypogammaglobulinemia, infection, and myelokathexis. It is caused mainly by heterozygous mutations at the C-terminus of the C-X-C chemokine receptor type 4 (CXCR4) gene. We described the detailed clinical, genetic, immunological and treatment characteristic of four WHIM patients from a single Chinese family. Here, we report four patients from a family carrying a variant of CXCR4 (c.1016_1017dupCT), which introduces a frameshift at codon V340, resulting in an extension of 14 amino acids (p.V340L fs*27). We provide and in-depth analysis of their clinical, genetic, immunological and treatment characteristic, noting that these patients exhibited an atypical clinical phenotype when compared to reported CXCR4R334X patients. Additionally, the frameshift variant CXCR4V340fs led to impaired receptor downregulation in patients' PBMCs, and in HEK293T cells transfected with the variant plasmids. Our study provided detailed clinical features of four CXCR4V340fs WHIM patients from one Chinese family who presented atypical phenotype and enrich the spectrum of WHIM syndrome.

The complex nature of CXCR4 mutations in WHIM syndrome.

Heterozygous autosomal dominant mutations in the CXCR4 gene cause WHIM syndrome, a severe combined immunodeficiency disorder. The mutations primarily affect the C-terminal region of the CXCR4 chemokine receptor, specifically several potential phosphorylation sites critical for agonist (CXCL12)-mediated receptor internalization and desensitization. Mutant receptors have a prolonged residence time on the cell surface, leading to hyperactive signaling that is responsible for some of the symptoms of WHIM syndrome. Recent studies have shown that the situation is more complex than originally thought, as mutant WHIM receptors and CXCR4 exhibit different dynamics at the cell membrane, which also influences their respective cellular functions. This review examines the functional mechanisms of CXCR4 and the impact of WHIM mutations in both physiological and pathological conditions.

EVALUATING A NEWBORN INFANT WITH PANCYTOPENIA FOR WHIM SYNDROME

EVALUATING A NEWBORN INFANT WITH PANCYTOPENIA FOR WHIM SYNDROME

Severe CD8+ T Lymphopenia in WHIM Syndrome Caused by Selective Sequestration in Primary Immune Organs.

Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome is an ultra-rare combined primary immunodeficiency disease caused by heterozygous gain-of-function mutations in the chemokine receptor CXCR4. WHIM patients typically present with recurrent acute infections associated with myelokathexis (severe neutropenia due to bone marrow retention of mature neutrophils). Severe lymphopenia is also common, but the only associated chronic opportunistic pathogen is human papillomavirus and mechanisms are not clearly defined. In this study, we show that WHIM mutations cause more severe CD8 than CD4 lymphopenia in WHIM patients and WHIM model mice. Mechanistic studies in mice revealed selective and WHIM allele dose-dependent accumulation of mature CD8 single-positive cells in thymus in a cell-intrinsic manner due to prolonged intrathymic residence, associated with increased CD8 single-positive thymocyte chemotactic responses invitro toward the CXCR4 ligand CXCL12. In addition, mature WHIM CD8+ T cells preferentially home to and are retained in the bone marrow in mice in a cell-intrinsic manner. Administration of the specific CXCR4 antagonist AMD3100 (plerixafor) in mice rapidly and transiently corrected T cell lymphopenia and the CD4/CD8 ratio. After lymphocytic choriomeningitis virus infection, we found no difference in memory CD8+ T cell differentiation or viral load between wild-type and WHIM model mice. Thus, lymphopenia in WHIM syndrome may involve severe CXCR4-dependent CD8+ T cell deficiency resulting in part from sequestration in the primary lymphoid organs, thymus, and bone marrow.

Results of a Phase 3 Trial of an Oral CXCR4 Antagonist, Mavorixafor, for Treatment of Patients With WHIM Syndrome

BackgroundWarts, Hypogammaglobulinemia, Infections, and Myelokathexis (WHIM) syndrome is a rare, combined immunodeficiency presenting with leukopenia and infections, predominately caused by gain-of-function variants in CXCR4. Mavorixafor, an investigational oral CXCR4 antagonist, demonstrated promising efficacy and safety profiles in a phase 2 trial for participants with WHIM syndrome. ObjectiveTo report results of the randomized, double-blind, multicenter, placebo-controlled period of a phase 3 study evaluating the efficacy and safety of mavorixafor in participants with WHIM syndrome (NCT03995108). MethodsParticipants aged ≥12 years with clinical diagnosis of WHIM syndrome, confirmed CXCR4 variant, and absolute neutrophil count (ANC) or total white blood cell (WBC) count ≤400 cells/µL at screening were eligible. Participants were randomized 1:1 to receive mavorixafor (>50 kg, 400 mg once daily [QD]; ≤50 kg, 200 mg QD) or placebo for 52 weeks. The primary endpoint was time above threshold ANC (TAT-ANC). Figure 1 shows study design and select secondary endpoints. ResultsOverall, 31 participants were randomized (mavorixafor, n = 14; placebo, n = 17) and received ≥1 dose of treatment (intent-to-treat population). The primary endpoint, mean TAT-ANC, was 15.04 (mavorixafor-group) vs 2.75 hours (placebo-group; P <.0001). Additionally, mean TAT absolute lymphocyte count (TAT-ALC) was 15.80 (mavorixafor-group) vs 4.55 hours (placebo-group; P < .0001). Mean absolute WBC count, ANC, and ALC increased from baseline into normal range and sustained at each timepoint assessed over 52 weeks with mavorixafor versus placebo. Compared with placebo-group, mavorixafor-group showed 60% lower annualized infection rate (least squares [LS] mean: mavorixafor, 1.7; placebo, 4.2; nominal P = .0072), and 40% lower total infection score, a combination of infection number and severity (LS mean [95% CI]: mavorixafor, 7.41 [1.64–13.19]; placebo, 12.27 [7.24–17.30]). Greater reduction in infection duration and type and antibiotic use was observed with mavorixafor versus placebo.No discontinuations occurred due to adverse events (AEs). No treatment-related serious AEs or treatment-limiting toxicities were observed (Table 1). [Display omitted] Table 1Overall summary of AEs from the randomized, placebo-controlled periodParticipants, n (%)abcdMavorixafor (n = 14)Placebo (n = 17)Total (n = 31)Any TEAEe14 (100.0)17 (100.0)31 (100.0)Treatment-related TEAEe7 (50.0)3 (17.6)10 (32.3)Any SAE5 (35.7)2 (11.8)7 (22.6)Treatment-related SAE0 (0)0 (0)0 (0)TEAE leading to treatment discontinuatione,f0 (0)0 (0)0 (0)Treatment-limiting toxicity0 (0)0 (0)0 (0)AE, adverse event; SAE, serious adverse event; TEAE, treatment-emergent adverse event.Data cutoff November 11, 2022.aSafety was evaluated in the safety population, defined as all participants who received ≥1 dose of study medication (either mavorixafor or placebo). Participants were analyzed according to the treatment they actually received.bPercentages were based on the number of participants in each analysis group.cAll AEs were coded using Medical Dictionary for Regulatory Activities Version 25.0.dIf a participant had ≥2 AEs, the participant is counted only once in a category for the n. The same participant may appear in different categories.eTEAEs were defined as any AEs that begin or worsen on or after the start of study drug through 10 days after the last dose of study drug.fOne participant had a TEAE that emerged during the randomized, placebo-controlled period but leading to treatment discontinuation after entering the open-label period. ConclusionsPrimary and first key secondary endpoints were met. Mavorixafor-group showed significantly higher mean TAT-ANC and TATALC and greater reduction in infection frequency, severity, and duration versus placebo-group. Mavorixafor was generally well tolerated over the 52-week treatment period. About 87% of eligible participants enrolled in the open-label extension.

WHIM Syndrome-linked CXCR4 mutations drive osteoporosis

WHIM Syndrome is a rare immunodeficiency caused by gain-of-function CXCR4 mutations. Here we report a decrease in bone mineral density in 25% of WHIM patients and bone defects leading to osteoporosis in a WHIM mouse model. Imbalanced bone tissue is observed in mutant mice combining reduced osteoprogenitor cells and increased osteoclast numbers. Mechanistically, impaired CXCR4 desensitization disrupts cell cycle progression and osteogenic commitment of skeletal stromal/stem cells, while increasing their pro-osteoclastogenic capacities. Impaired osteogenic differentiation is evidenced in primary bone marrow stromal cells from WHIM patients. In mice, chronic treatment with the CXCR4 antagonist AMD3100 normalizes in vitro osteogenic fate of mutant skeletal stromal/stem cells and reverses in vivo the loss of skeletal cells, demonstrating that proper CXCR4 desensitization is required for the osteogenic specification of skeletal stromal/stem cells. Our study provides mechanistic insights into how CXCR4 signaling regulates the osteogenic fate of skeletal cells and the balance between bone formation and resorption.

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

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