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

ABSTRACT: We 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.

Heterozygous variants of CLPB are a cause of severe congenital neutropenia.

Severe congenital neutropenia is an inborn disorder of granulopoiesis. Approximately one third of cases do not have a known genetic cause. Exome sequencing of 104 persons with congenital neutropenia identified heterozygous missense variants of CLPB (caseinolytic peptidase B) in 5 severe congenital neutropenia cases, with 5 more cases identified through additional sequencing efforts or clinical sequencing. CLPB encodes an adenosine triphosphatase that is implicated in protein folding and mitochondrial function. Prior studies showed that biallelic mutations of CLPB are associated with a syndrome of 3-methylglutaconic aciduria, cataracts, neurologic disease, and variable neutropenia. However, 3-methylglutaconic aciduria was not observed and, other than neutropenia, these clinical features were uncommon in our series. Moreover, the CLPB variants are distinct, consisting of heterozygous variants that cluster near the adenosine triphosphate-binding pocket. Both genetic loss of CLPB and expression of CLPB variants result in impaired granulocytic differentiation of human hematopoietic progenitor cells and increased apoptosis. These CLPB variants associate with wild-type CLPB and inhibit its adenosine triphosphatase and disaggregase activity in a dominant-negative fashion. Finally, expression of CLPB variants is associated with impaired mitochondrial function but does not render cells more sensitive to endoplasmic reticulum stress. Together, these data show that heterozygous CLPB variants are a new and relatively common cause of congenital neutropenia and should be considered in the evaluation of patients with congenital neutropenia.

Disease Progression of WHIM Syndrome in an International Cohort of 66 Pediatric and Adult Patients.

Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome (WS) is a combined immunodeficiency caused by gain-of-function mutations in the C-X-C chemokine receptor type 4 (CXCR4) gene. We characterize a unique international cohort of 66 patients, including 57 (86%) cases previously unreported, with variable clinical phenotypes. Of 17 distinct CXCR4 genetic variants within our cohort, 11 were novel pathogenic variants affecting 15 individuals (23%). All variants affect the same CXCR4 region and impair CXCR4 internalization resulting in hyperactive signaling. The median age of diagnosis in our cohort (5.5 years) indicates WHIM syndrome can commonly present in childhood, although some patients are not diagnosed until adulthood. The prevalence and mean age of recognition and/or onset of clinical manifestations within our cohort were infections 88%/1.6 years, neutropenia 98%/3.8 years, lymphopenia 88%/5.0 years, and warts 40%/12.1 years. However, we report greater prevalence and variety of autoimmune complications of WHIM syndrome (21.2%) than reported previously. Patients with versus without family history of WHIM syndrome were diagnosed earlier (22%, average age 1.3 years versus 78%, average age 5 years, respectively). Patients with a family history of WHIM syndrome also received earlier treatment, experienced less hospitalization, and had less end-organ damage. This observation reinforces previous reports that early treatment for WHIM syndrome improves outcomes. Only one patient died; death was attributed to complications of hematopoietic stem cell transplantation. The variable expressivity of WHIM syndrome in pediatric patients delays their diagnosis and therapy. Early-onset bacterial infections with severe neutropenia and/or lymphopenia should prompt genetic testing for WHIM syndrome, even in the absence of warts.

Results of a phase 2 trial of an oral CXCR4 antagonist, mavorixafor, for treatment of WHIM syndrome.

Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome is a rare primary immunodeficiency caused by gain-of-function mutations in the CXCR4 gene. We report the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary efficacy of mavorixafor from a phase 2 open-label dose-escalation and extension study in 8 adult patients with genetically confirmed WHIM syndrome. Mavorixafor is an oral small molecule selective antagonist of the CXCR4 receptor that increases mobilization and trafficking of white blood cells from the bone marrow. Patients received escalating doses of mavorixafor, up to 400 mg once daily. Five patients continued on the extension study for up to 28.6 months. Mavorixafor was well tolerated with no treatment-related serious adverse events. At a median follow-up of 16.5 months, we observed dose-dependent increases in absolute neutrophil count (ANC) and absolute lymphocyte count (ALC). At doses ≥300 mg/d, ANC was maintained at >500 cells per microliter for a median of 12.6 hours, and ALC was maintained at >1000 cells per microliter for up to 16.9 hours. Continued follow-up on the extension study resulted in a yearly infection rate that decreased from 4.63 events (95% confidence interval, 3.3-6.3) in the 12 months prior to the trial to 2.27 events (95% confidence interval, 1.4-3.5) for patients on effective doses. We observed an average 75% reduction in the number of cutaneous warts. This study demonstrates that mavorixafor, 400 mg once daily, mobilizes neutrophil and lymphocytes in adult patients with WHIM syndrome and provides preliminary evidence of clinical benefit for patients on long-term therapy. The trial was registered at www.clinicaltrials.gov as #NCT03005327.

A prospective study to evaluate febrile neutropenia incidence in patients receiving pegfilgrastim on-body injector vs other choices.

PURPOSE: We evaluated the incidence of febrile neutropenia (FN) and related clinical outcomes among patients treated with myelosuppressive chemotherapy for nonmyeloid malignancies who received pegfilgrastim on-body injector (OBI) or other options (Other) for FN prophylaxis. METHODS: In this prospective observational study, adult patients with breast, prostate, or lung cancer, or non-Hodgkin lymphoma at risk for FN were stratified into subgroups based on FN prophylaxis used in the first chemotherapy cycle: pegfilgrastim OBI vs Other (pegfilgrastim or biosimilar pegfilgrastim prefilled syringe, daily filgrastim, or no granulocyte colony-stimulating factor [G-CSF]) for up to 4 planned chemotherapy cycles. RESULTS: This US study enrolled 2575 eligible patients (OBI, 1624; Other, 951). FN incidence was lower in the OBI group (6.4% [95% CI, 5.2-7.6%]) than in the Other group (9.4% [7.5-11.2%]), with a relative risk (RR) of 0.66 (0.47-0.91; p = .006). A decreased risk of dose delays among patients receiving pegfilgrastim OBI vs Other was observed (RR for ≥ 5 days: 0.64 [0.42-0.96], p = .023; RR for ≥ 7 days: 0.62 [0.40-0.91], p = .016). Adherence, defined as G-CSF support for all chemotherapy cycles, was 94.0% (92.9-95.2%) in the OBI group compared with 58.4% (55.2-61.5%) in the Other group. Compliance with pegfilgrastim, defined as administration the day after chemotherapy, was 88.3% in the OBI group and 48.8% in the prefilled syringe group. CONCLUSION: Patients receiving pegfilgrastim OBI had a lower incidence of FN compared with those receiving alternatives. The OBI was associated with improved adherence to and compliance with clinically recommended G-CSF prophylaxis.

A prospective cohort study to evaluate the incidence of febrile neutropenia in patients receiving pegfilgrastim on-body injector versus other options for prophylaxis of febrile neutropenia: breast cancer subgroup analysis.

BACKGROUND: Breast cancer chemotherapy often carries a high risk of febrile neutropenia (FN); guidelines recommend prophylaxis with granulocyte colony-stimulating factor (G-CSF), such as pegfilgrastim. Neulasta® Onpro® on-body injector (OBI) is a delivery device administering pegfilgrastim approximately 27 h after application. METHODS: This prospective study examined patients with breast cancer who received chemotherapy with a high risk of FN, receiving OBI ("OBI") or other options (other G-CSF or none; "other"). The primary endpoint was FN incidence; secondary endpoints included chemotherapy delivery, adherence (G-CSF in all cycles), compliance (G-CSF day after chemotherapy), and FN incidence in patients receiving curative or palliative treatment. RESULTS: A total of 1776 patients with breast cancer were enrolled (OBI, n = 1196; other, n = 580). Across all cycles, FN incidence was lower for OBI (4.4% [95% CI, 3.3-5.6%]) than other (7.4% [5.3-9.6%]). For curative treatment, the FN incidence across all cycles was lower for OBI (4.6% [3.4-5.8%]) than for other (7.1% [5.0-9.3%]). For palliative treatment (OBI, n = 33; other, n = 20), 3 patients (15%) in the other and none in the OBI group had FN. After adjusting for baseline covariates, FN incidence remained lower for OBI (4.6% [3.5-6.1%]) versus other (7.8% [5.7-10.5%]). Adherence was higher for OBI (93.8%) than for other G-CSF (69.8%), as was compliance (90.5 and 53.2%, respectively). Chemotherapy dose delays/reductions were similar for OBI (4.7%/32.3%, respectively) and other (4.7%/30.0%) groups. CONCLUSION: Pegfilgrastim OBI was associated with a lower FN incidence in patients with breast cancer compared to other options for FN prophylaxis. TRIAL REGISTRATION: www. CLINICALTRIALS: gov , NCT02178475, registered 30 June, 2014.

Family studies of warts, hypogammaglobulinemia, immunodeficiency, myelokathexis syndrome.

PURPOSE OF REVIEW: WHIM syndrome (warts, hypogammaglobulinemia, immunodeficiency, myelokathexis, or WHIMs) is a very rare autosomal dominant immunodeficiency disorder attributable to mutations in CXCR4. We reviewed clinical manifestations in 24 patients in 9 families to expand understanding of this syndrome. RECENT FINDINGS: Warts, cellulitis and respiratory infections are common in patients with WHIMs. Less commonly these patients have congenital heart disease, human papilloma virus-associated malignancies (cervical and vulvular) and lymphomas. Hearing loss because of recurrent otitis media is another important complication. Treatment with granulocyte colony-stimulating factor is controversial; this review indicates that it is effective to prevent and treat infections based upon long-term observations of patients enrolled in the Severe Chronic Neutropenia International Registry. Understanding the natural history and diversity of this syndrome are important for ongoing clinical trials of novel agents to treat WHIMs. SUMMARY: WHIM syndrome has diverse manifestations; some features occur consistently in almost all patients, for example, neutropenia, lymphocytopenia and mild hypogammaglobulinemia. However, the clinical consequences are quite variable across patient cohorts and within families. Each complication is important as a cause for morbidity and a source for patient and family concerns.

Registries for study of nonmalignant hematological diseases: the example of the Severe Chronic Neutropenia International Registry.

PURPOSE OF REVIEW: Registries provide 'real world' perspectives on the natural history and outcomes for many clinical conditions. The purpose of this review is to identify registries for nonmalignant hematological disease and to describe the operation of a successful long-term registry for patients with severe chronic neutropenia. RECENT FINDINGS: There was an upswing in registries about 20 years ago, based on optimism about their utility to improve patient care. To show value, registries must define outcomes for populations of patients with specific medical conditions and the effects of treatment. This is challenging for many reasons. The Severe Chronic Neutropenia International Registry is an example of a successful registry. This report describes underlying reasons for its success. SUMMARY: Registries are important to organize and analyze clinical information across geographic, ethnic and social boundaries. They are also challenging to organize, administer and support.

Somatic mutations and clonal hematopoiesis in congenital neutropenia.

Severe congenital neutropenia (SCN) and Shwachman-Diamond syndrome (SDS) are congenital neutropenia syndromes with a high rate of leukemic transformation. Hematopoietic stressors may contribute to leukemic transformation by increasing the mutation rate in hematopoietic stem/progenitor cells (HSPCs) and/or by promoting clonal hematopoiesis. We sequenced the exome of individual hematopoietic colonies derived from 13 patients with congenital neutropenia to measure total mutation burden and performed error-corrected sequencing on a panel of 46 genes on 80 patients with congenital neutropenia to assess for clonal hematopoiesis. An average of 3.6 ± 1.2 somatic mutations per exome was identified in HSPCs from patients with SCN compared with 3.9 ± 0.4 for healthy controls (P = NS). Clonal hematopoiesis due to mutations in TP53 was present in 48% (13/27) of patients with SDS but was not seen in healthy controls (0/17, P < .001) or patients with SCN (0/40, P < .001). Our SDS cohort was young (median age 6.3 years), and many of the patients had multiple TP53 mutations. Conversely, clonal hematopoiesis due to mutations of CSF3R was present in patients with SCN but was not detected in healthy controls or patients with SDS. These data show that hematopoietic stress, including granulocyte colony-stimulating factor, do not increase the mutation burden in HSPCs in congenital neutropenia. Rather, distinct hematopoietic stressors result in the selective expansion of HSPCs carrying specific gene mutations. In particular, in SDS there is enormous selective pressure to expand TP53-mutated HSPCs, suggesting that acquisition of TP53 mutations is an early, likely initiating event, in the transformation to myelodysplastic syndrome/acute myeloid leukemia in patients with SDS.

CRISPR/Cas9-mediated ELANE knockout enables neutrophilic maturation of primary hematopoietic stem and progenitor cells and induced pluripotent stem cells of severe congenital neutropenia patients.

A Autosomal-dominant ELANE mutations are the most common cause of severe congenital neutropenia. Although the majority of congenital neutropenia patients respond to daily granulocyte colony stimulating factor, approximately 15 % do not respond to this cytokine at doses up to 50 µg/kg/day and approximately 15 % of patients will develop myelodysplasia or acute myeloid leukemia. "Maturation arrest," the failure of the marrow myeloid progenitors to form mature neutrophils, is a consistent feature of ELANE associated congenital neutropenia. As mutant neutrophil elastase is the cause of this abnormality, we hypothesized that ELANE associated neutropenia could be treated and "maturation arrest" corrected by a CRISPR/Cas9-sgRNA ribonucleoprotein mediated ELANE knockout. To examine this hypothesis, we used induced pluripotent stem cells from two congenital neutropenia patients and primary hematopoietic stem and progenitor cells from four congenital neutropenia patients harboring ELANE mutations as well as HL60 cells expressing mutant ELANE We observed that granulocytic differentiation of ELANE knockout induced pluripotent stem cells and primary hematopoietic stem and progenitor cells were comparable to healthy individuals. Phagocytic functions, ROS production, and chemotaxis of the ELANE KO (knockout) neutrophils were also normal. Knockdown of ELANE in the mutant ELANE expressing HL60 cells also allowed full maturation and formation of abundant neutrophils. These observations suggest that ex vivo CRISPR/Cas9 RNP based ELANE knockout of patients' primary hematopoietic stem and progenitor cells followed by autologous transplantation may be an alternative therapy for congenital neutropenia.

Neutropenia Is an Underrecognized Finding in Pediatric Primary Immunodeficiency Diseases: An Analysis of the United States Immunodeficiency Network Registry.

BACKGROUND: The frequency of neutropenia in pediatric primary immunodeficiency disorders (PIDDs) is unknown and potentially underappreciated. Our study aimed to determine the overall frequency and severity of neutropenia in children diagnosed with a PIDD entered in the United States Immunodeficiency Network (USIDNET) patient registry. PROCEDURE: Neutropenia data and demographic/clinical information from 1145 patients younger than 21 years of age was obtained from the USIDNET registry. RESULTS: Neutropenia is more common in PIDD patients entered within the USIDNET registry than previously appreciated. There was a >10% occurrence rate of neutropenia in all broad primary immunodeficiency categories as well as in nearly all individual PIDDs. Neutropenia frequency was greater in African American pediatric PIDD patients than in white or Asian patients. The degree of neutropenia did not associate with mortality in pediatric patients with a PIDD. CONCLUSION: Although our study did not assess the frequency of PIDD in patients presenting with neutropenia, the possibility of a primary immune disorder should be considered in patients with idiopathic neutropenia.

Neutropenia in Barth syndrome: characteristics, risks, and management.

PURPOSE OF REVIEW: Barth syndrome (BTHS) is an X-linked disease characterized by defective remodeling of phospholipid side chains in mitochondrial membranes. Major features include neutropenia, dilated cardiomyopathy, motor delay and proximal myopathy, feeding problems, and constitutional growth delay. We conducted this review of neutropenia in BTHS to aid in the diagnosis of this disease, and to improve understanding of both the consequences of neutropenia and the benefits of treatment with granulocyte colony-stimulating factor (G-CSF). RECENT FINDINGS: In 88 patients with BTHS, neutropenia, that is, at least one count below 1.5 × 10/l, was detected in 74 (84%) and 44% had severe chronic neutropenia, with multiple counts below 0.5 × 10/l. The pattern of neutropenia varied between intermittent and unpredictable, chronic and severe, or cyclical with mathematically regular oscillations. Monocytosis, that is, monocytes more than 1.0 × 10/l, was observed at least once in 64 of 85 (75%) patients. G-CSF was administered to 39 of 88 patients (44%). Weekly average G-CSF doses ranged from 0.12 to 10.92 µg/kg/day (mean 1.16 µg/kg/day, median 1.16 µg/kg/day). Antibiotic prophylaxis was additionally employed in 21 of 26 neutropenic patients. Pretreatment bone marrow evaluations predominantly showed reduced myeloid maturation which normalized on G-CSF therapy in seven of 13 examined. Consistent clinical improvement, with reduced signs and symptoms of infections, was observed in response to prophylactic G-CSF ±â€Šprophylactic antibiotics. However, despite G-CSF and antibiotics, one adult patient died with multiple infections related to indwelling medical devices and gastrostomy site infection after 15.5 years on G-CSF and a pediatric patient required gastrostomy removal for recurrent abdominal wall cellulitis. SUMMARY: BTHS should be considered in any men with neutropenia accompanied by any of the characteristic features of this syndrome. Prophylaxis with G-CSF ±â€Šantibiotics prevents serious bacterial infections in the more severe neutropenic patients although infections remain a threat even in patients who are very compliant with therapy, especially in those with indwelling devices.

Neutropenia in glycogen storage disease Ib: outcomes for patients treated with granulocyte colony-stimulating factor.

PURPOSE OF REVIEW: Glycogen storage disease Ib (GSD Ib) is characterized by hepatomegaly, hypoglycemia, neutropenia, enterocolitis and recurrent bacterial infections. It is attributable to mutations in G6PT1, the gene for the glucose-6-phosphate transporter responsible for transport of glucose into the endoplasmic reticulum. Neutropenia in GSD Ib is now frequently treated with granulocyte colony-stimulating factor (G-CSF). We formed a cooperative group to review outcomes of the long-term treatment of GSD Ib patients treated with G-CSF. RECENT FINDINGS: The study enrolled 103 patients (48 men and 55 women), including 47 currently adult patients. All of these patients were treated with G-CSF, starting at a median age of 3.8 years (range 0.04-33.9 years) with a median dose of 3.0 mcg/kg/day (range 0.01-93.1 mcg/kg/day) for a median of 10.3 years (range 0.01-29.3 years). Neutrophils increased in response to G-CSF in all patients (median values before G-CSF 0.2 × 10/l, on G-CSF 1.20 x 10/l). Treatment increased spleen size (before G-CSF, 47%, on treatment on G-CSF 76%), and splenomegaly was the dose-limiting adverse effect of treatment (pain and early satiety). Clinical observations and records attest to reduce frequency of infectious events and the severity of inflammatory bowel symptoms, but fever and recurrent infections remain a significant problem. In the cohort of patients followed carefully through the Severe Chronic Neutropenia International Registry, four patients have developed myelodysplasia or acute myeloid leukemia and we are aware of four other cases, (altogether seven on G-CSF, one never treated with G-CSF). Liver transplantation in five patients did not correct neutropenia. Four patients had hematopoietic stem cell transplantation; two adults and two children were transplanted; one adult and one child survived. SUMMARY: GSD Ib is a complex disorder of glucose metabolism causing severe chronic neutropenia. G-CSF is effective to raise blood neutrophil counts and reduce fevers and infections in most patients. In conjunction with other therapies (salicylates, mesalamine sulfasalazine and prednisone), G-CSF ameliorates inflammatory bowel symptoms, but doses must be limited because it increases spleen size associated with abdominal pain.

A systematic literature review of the efficacy, effectiveness, and safety of filgrastim.

PURPOSE: Filgrastim (NEUPOGEN®) is the originator recombinant human granulocyte colony-stimulating factor widely used for preventing neutropenia-related infections and mobilizing hematopoietic stem cells. This report presents findings of a systematic literature review and meta-analysis of efficacy and safety of originator filgrastim to update previous reports. METHODS: A literature search of electronic databases, congress abstracts, and bibliographies of recent reviews was conducted to identify English-language reports of clinical trials and observational studies evaluating filgrastim in its US-approved indications up to February 2015. Two independent reviewers assessed titles/abstracts and full texts of publications, and extracted data from studies that compared originator filgrastim vs placebo or no treatment. For outcomes with sufficient homogeneous data reported across studies, meta-analysis was performed and relative risk (RR) determined. Data were summarized descriptively for all other evaluated outcomes. RESULTS: A total of 1194 unique articles evaluating originator filgrastim were identified, with 25 meeting eligibility criteria for data extraction: 18 randomized controlled trials, 2 nonrandomized clinical trials, and 5 observational studies. In chemotherapy-induced neutropenia (CIN), filgrastim vs placebo or no treatment significantly reduced febrile neutropenia incidence (RR 0.63, 95% CI 0.53-0.75) and grade 3 or 4 neutropenia incidence (RR 0.50, 95% CI 0.37-0.68). The most commonly reported adverse event (AE) with filgrastim was bone pain (RR 2.61, 95% CI 1.29-5.27 in CIN). Additional efficacy and safety outcomes are described within indications. CONCLUSIONS: This systematic literature review and meta-analysis confirms and updates previous reports on the efficacy and safety of originator filgrastim. Bone pain was the commonly reported AE associated with filgrastim use.

An update on the diagnosis and treatment of chronic idiopathic neutropenia.

PURPOSE OF REVIEW: Neutropenia lasting for at least for 3 months and not attributable to drugs or a specific genetic, infectious, inflammatory, autoimmune or malignant cause is called chronic idiopathic neutropenia (CIN). CIN and autoimmune neutropenia (AIN) are very similar and overlapping conditions. The clinical consequences depend upon the severity of neutropenia, but it is not considered a premalignant condition. RECENT FINDINGS: Long-term observational studies in children indicate that the disease often lasts for 3-5 years in children, then spontaneously remits, but it rarely remits in adult cases. The value of antineutrophil antibody testing in both children and adults is uncertain. Most recent data suggest that CIN and AIN are immune-mediated diseases, but there are no new clinical or genetic tests to aid in diagnosis. Treatment with granulocyte colony stimulating factor (G-CSF) is effective to increase blood neutrophils in almost all cases; this treatment is reserved, however, for patients with both neutropenia and evidence of recurrent fevers, inflammatory symptoms and infections. There is little or no evidence to indicate that G-CSF treatment predisposes to myeloid malignancies in this population. SUMMARY: It is important to recognize CIN and AIN, the most common causes of chronic neutropenia in both children and adults. If the neutropenia is not severe, that is more than 0.5 × 10/l, most patients can be observed and not treated prophylactically with antibiotics or a growth factor. When neutropenia is severe, treatment with G-CSF is often beneficial.

Association Between Absolute Neutrophil Count and Variation at TCIRG1: The NHLBI Exome Sequencing Project.

Neutrophils are a key component of innate immunity. Individuals with low neutrophil count are susceptible to frequent infections. Linkage and association between congenital neutropenia and a single rare missense variant in TCIRG1 have been reported in a single family. Here, we report on nine rare missense variants at evolutionarily conserved sites in TCIRG1 that are associated with lower absolute neutrophil count (ANC; p = 0.005) in 1,058 participants from three cohorts: Atherosclerosis Risk in Communities (ARIC), Coronary Artery Risk Development in Young Adults (CARDIA), and Jackson Heart Study (JHS) of the NHLBI Grand Opportunity Exome Sequencing Project (GO ESP). These results validate the effects of TCIRG1 coding variation on ANC and suggest that this gene may be associated with a spectrum of mild to severe effects on ANC.

How I manage children with neutropenia.

Neutropenia, usually defined as a blood neutrophil count <1·5 × 109 /l, is a common medical problem for children and adults. There are many causes for neutropenia, and at each stage in life the clinical pattern of causes and consequences differs significantly. I recommend utilizing the age of the child and clinical observations for the preliminary diagnosis and primary management. In premature infants, neutropenia is quite common and contributes to the risk of sepsis with necrotizing enterocolitis. At birth and for the first few months of life, neutropenia is often attributable to isoimmune or alloimmune mechanisms and predisposes to the risk of severe bacterial infections. Thereafter when a child is discovered to have neutropenia, often associated with relatively minor symptoms, it is usually attributed to autoimmune disorder or viral infection. The congenital neutropenia syndromes are usually recognized when there are recurrent infections, the neutropenia is severe and there are congenital anomalies suggesting a genetic disorder. This review focuses on the key clinical finding and laboratory tests for diagnosis with commentaries on treatment, particularly the use of granulocyte colony-stimulating factor to treat childhood neutropenia.

How I diagnose and treat neutropenia.

PURPOSE OF REVIEW: Neutropenia absolute neutrophil count (ANC) less than 1.5 × 10(9)/l is a common hematological finding, and severe neutropenia, that is, ANC less than 0.5 × 10(9)/l is a well known risk factor for susceptibility to bacterial infections. This review provides a succinct clinical approach to the diagnosis and treatment of neutropenia with specific recommendations on the treatment of severe chronic neutropenia with the myeloid growth factor, granulocyte colony-stimulating factor (G-CSF). RECENT FINDINGS: Experts agree that patients with acute febrile neutropenia should be treated with antibiotics and that patients at high risk of severe neutropenia (>20% risk) after myelosuppressive chemotherapy should be treated prophylactically with a myeloid growth factor, usually G-CSF. The diversity of causes and consequences of chronic neutropenia make the diagnosis and management of these patients more complicated. SUMMARY: The review provides a stepwise approach to neutropenia focusing first on reaching a provisional diagnosis and treatment plan then steps to a final diagnosis. It also provides specific recommendations on the treatment of severe chronic neutropenia with G-CSF.

Cooperativity of RUNX1 and CSF3R mutations in severe congenital neutropenia: a unique pathway in myeloid leukemogenesis.

Severe congenital neutropenia (CN) is a preleukemic bone marrow failure syndrome with a 20% risk of evolving into leukemia or myelodysplastic syndrome (MDS). Patterns of acquisition of leukemia-associated mutations were investigated using next-generation deep-sequencing in 31 CN patients who developed leukemia or MDS. Twenty (64.5%) of the 31 patients had mutations in RUNX1. A majority of patients with RUNX1 mutations (80.5%) also had acquired CSF3R mutations. In contrast to their high frequency in CN patients who developed leukemia or MDS, RUNX1 mutations were found in only 9 of 307 (2.9%) patients with de novo pediatric acute myeloid leukemia. A sequential analysis at stages prior to overt leukemia revealed RUNX1 mutations to be late events in leukemic transformation. Single-cell analyses in 2 patients showed that RUNX1 and CSF3R mutations were present in the same malignant clone. Functional studies demonstrated elevated granulocyte colony-stimulating factor (G-CSF)-induced proliferation with diminished myeloid differentiation of hematopoietic CD34(+) cells coexpressing mutated forms of RUNX1 and CSF3R. The high frequency of cooperating RUNX1 and CSF3R mutations in CN patients suggests a novel molecular pathway of leukemogenesis: mutations in the hematopoietic cytokine receptor (G-CSFR) in combination with the second mutations in the downstream hematopoietic transcription fator (RUNX1). The detection of both RUNX1 and CSF3R mutations could be used as a marker for identifying CN patients with a high risk of progressing to leukemia or MDS.