Impaired myelopoiesis in congenital neutropenia: insights into clonal and malignant hematopoiesis

A common feature of both congenital and acquired forms of bone marrow failure is an increased risk of developing acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Indeed, the development of MDS or AML is now the major cause of mortality in patients with congenital neutropenia. Thus, there is a pressing clinical need to develop better strategies to prevent, diagnose early, and treat MDS/AML in patients with congenital neutropenia and other bone marrow failure syndromes. Here, we discuss recent data characterizing clonal hematopoiesis and progression to myeloid malignancy in congenital neutropenia, focusing on severe congenital neutropenia (SCN) and Shwachman-Diamond syndrome. We summarize recent studies showing excellent outcomes after allogenic hematopoietic stem cell transplantation for many (but not all) patients with congenital neutropenia, including patients with SCN with active myeloid malignancy who underwent transplantation. Finally, we discuss how these new data inform the current clinical management of patients with congenital neutropenia.

ELANE Neutropenia Beyond the Classification into Cyclic Neutropenia and Severe Congenital Neutropenia: The Inconstant Time Clock

Introduction: ELANE neutropenia represents the cause of 25-30% of the cases of congenital neutropenia. Classically, its appears in the literature as in OMIM, under two distinct entities: Severe congenital neutropenia (SCN) and cyclic neutropenia (CyN). The delineation between the 2 entities is the "cyclicity" i.e. the periodic variation of the absolute neutrophils count (ANC), also called a 21-day time clock 1. However, it is extremely difficult to obtain enough sequential complete blood counts (CBC) at the onset of the disease, during an enough length period, while the patient is not experiencing a severe infection or receiving GCSF therapy. The purpose of our study is to analyze the ANC periodicity at the onset of the disease, prior to the initiation of GCSF in a cohort of patients with ELANE neutropenia. Methods : Available data from the patients, with ELANE class 4 and 5 variants, enrolled in the French Severe Chronic Neutropenia Registry, were analysed. The final diagnostic of CyN and SCN was performed considering all the follow up period (median 16.7 years) and based on the presence of recurrent periodic variation of ANC in the absence of GCSF therapy. CyN was defined as multiple documented ANCs >500 cells/mm 3 , with intermittent ANC variation (n=49), while SCN is defined as ANC persistently <500 cells/mm 3 (n=94). In case of irregularity (i.e. not a regular periodic pattern during all the follow up), the classification takes in consideration the majority of the follow up. A comprehensive analysis of the infectious profile is available elsewhere 2. We were focused here on the diagnostic period (roughly the 2 first months since the diagnosis). We have analysed the initial blood count of the patients and cast the patients by categories if at least 4 ANCs can be evaluated. ANC oscillations defined 4 groups: Group 1: oscillation of ANC values above and below 500 ANC/mm 3 for at least 2 cycles lead to consider the patient as Cyclic; Group 2: clear oscillation of ANC values above and below 200 ANC/mm 3 (but ever<500 ANC/mm 3) for at least 2 cycles; Group 3: no oscillation of ANC values whose level are ever below 500 ANC/mm 3; Group 4: Early GCSF treatment. Results : Among the 143 patients enrolled in this study (Table 1), 137 have at least 4 CBC evaluable during the diagnosis period, including 30 who have been treated almost front line after diagnosis of neutropenia by GCSF hampering evaluation of periodicity. Such patients were all initially considered as SCN. Among the 67 finally classified as SCN, 28 (27.38%) showed an oscillation pattern (group 1), 14 (15.48%) showed minor oscillations (group 2), while 25 (30.95%) had a persistent and severe neutropenia (group 3). Among the 40 CyN, 1 have showed minor oscillations (group 2) below 500/mm 3, while 3 had a persistent and severe neutropenia (group 3). Globally, 32 /107 patients were miss- classified at diagnosis compare to the final diagnosis. Additional data shows that many health indicators could not be deducted from the initial classification like the infections rate, the use of GCSF, the death rate, the sequels rate. Conclusions: Periodic variation of ANC despite being the criteria to define the sub type of ELANE neutropenia is difficult to evaluate at the initial presentation of the disease. In addition, cyclicity is not a permanent feature in ELANE neutropenia, some patients being cyclic only for a certain time in their life span. It results a high rate of miss classification if we compare the initial diagnostic period and all the medical history of the patients. Noteworthy, the rate of several severe complications is not so clearly different between diagnosis sub categories. We propose to consider ELANE neutropenia as a unique disease characterized by a clinical spectrum ranging from more severe forms (corresponding to SCN) to milder forms, the latter often characterized at onset by ANC fluctuations. In addition, some intermediate severity forms could be characterized by minor oscillations. References 1 Horwitz M, Benson KF, Person RE, Aprikyan AG, Dale DC. Mutations in ELA2, encoding neutrophil elastase, define a 21-day biological clock in cyclic haematopoiesis. Nat.Genet. 1999;23:433-436. 2 Rotulo GA, Plat G, Beaupain B et al. Recurrent bacterial infections, but not fungal infections, characterise patients with ELANE-related neutropenia: a French Severe Chronic Neutropenia Registry study. Br J Haematol. 2021 doi: 10.1111/bjh.17695 Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Efficacy of Low-Dose rhGM-CSF Treatment in a Patient With Severe Congenital Neutropenia Due to CSF3R Deficiency: Case Report of a Novel Biallelic CSF3R Mutation and Literature Review

This study reports the clinical manifestations, genetics, and efficacy of treatment with the efficacy of recombinant human granulocyte macrophage colony-stimulating factor (rhGM-GSF) of a 2-year-old female patient with severe congenital neutropenia (SCN) type 7 (SCN7) caused by novel biallelic mutations in the colony-stimulating factor 3 receptor (CSF3R) gene. Genetic diagnosis of the patient was performed by whole-exome and Sanger sequencing. Expression of the CSF3R gene in the peripheral neutrophils of the patient was detected by real-time PCR and Western blotting. The patient presented with recurrent suppurative tonsillitis and decreased absolute neutrophil count <0.5 × 109/L. Novel heterozygous mutations were found to be inherited from each parent (maternal c.690delC [p.met231Cysfs*32] and paternal c.64+5G>A). The patient's neutrophils had lower CSF3R mRNA and protein levels than those of the parents. Low-dose rhGM-CSF (3 μg/kg/day once a week) prevented recurrent infection in the patient. These results demonstrate that the clinical manifestations of SCN7 with biallelic CSF3R mutations and downregulated CSF3R can be effectively treated with rhGM-CSF.

Neutropenia in children: acquired neutropenia

Neutropenia is defined as a reduction in the absolute neutrophil count (ANC) below 1,500 cells/mcl in the blood. Neutropenia is a common laboratory finding in children. It is important to distinguish transient and benign causes from severe congenital neutropenia. Neutropenia can be classified in asymptomatic (mild), moderate, and severe form, the susceptibility to infection depending on ANC. Neutropenia can be either acquired or congenital. Infection, drugs, and immune disorders are the most common acquired causes while congenital causes are rare and confined mostly to infants and children. Transient neutropenia often accompanies viral infections in children, manifested in the period of acute viremia. Young children are characterized by autoimmune neutropenia (AIN), which has a benign course and a favorable prognosis. Autoimmune neutropenia is characterized by a decrease in the number of neutrophils as a result of the destruction of neutrophils in the peripheral blood by antineutrophil antibodies. The duration of AIN is usually 3–5 years. This is a self-limiting disease that in most cases does not require treatment. Despite the benign course, serious infectious complications can occur. Treatment of myeloid growth factors should be started after a previous bone marrow aspiration biopsy in children with severe infections or requiring surgical intervention. High doses of intravenous immunoglobulin and corticosteroids may be effective in treating AIN in patients with life-threating infections. The danger to the patient depends on the etiology, ANC and bone marrow status. The risk of infections is significantly increased in patients with ACN less than 500 cells/μ1. The most common loci of infections include the oral mucosa, skin, perirectal area, perineum. Oral ulcers and gingivitis are characteristic signs of clinically significant neutropenia, requiring the exclusion of its congenital causes. Severe infections in patients with neutropenia are caused by pyogenic or intestinal bacteria and Candida species. It is important to distinguish between transient or benign causes and severe congenital neutropenia or neutropenia associated with serious haematological or systemic disease. Clarification of the cause of neutropenia is important for determining management and prognosis. No conflict of interest was declared by the author. Key words: neutropenia, children, immunodeficiency, autoimmune neutropenia.

Severe Congenital Neutropenia Due To G6PC3 Deficiency Case Series of Five Patients and Literature Review

Glucose-6-phosphate catalytic subunit 3 (G6PC3) deficiency is characterized by severe congenital neutropenia with recurrent pyogenic infections, a prominent superficial venous pattern, and cardiovascular and urogenital malformations, caused by an alteration of glucose homeostasis, with increased endoplasmic reticulum stress and cell apoptosis. We describe five new cases from Mexico, and review 89 more patients reported in the past decade, to delineate the most frequent laboratory and genetic features, their treatment, and outcomes, and to expand the knowledge of syndromic and non-syndromic phenotypes in these patients.

Novel G6PC3 Mutations in patients with Congenital Neutropenia: Case reports and Review of the Literature

Background: Severe congenital neutropenia (SCN4) caused by mutations in glucose-6-phosphatase catalytic subunit 3 (G6PC3) is characterized by recurrent infections due to severe neutropenia, and it may be accompanied by other extra-hematopoietic manifestations; including structural heart defects, urogenital abnormalities, prominent superficial venous markings, growth retention, and inflammatory bowel diseases with rare incidence. The homozygous or compound heterozygous mutations of G6PC3 are responsible for most cases of autosomal recessive SCN4. Herein, we present two cases of SCN4 affected by novel mutations in the G6PC3, in addition to a summarized list of variants in G6PC3 gene that are reported as pathogenic and related to the SCN4 phenotype. Case presentation: Herein we present two cases of SCN4; the first case was a three-months old boy with severe neutropenia and prior history of hospitalization due to umbilical separation, umbilical herniation, omphalitis, and pyelonephritis; and the second case was an eight-year-old with a history of neutropenia, recurrent and severe episodes of intractable diarrhea, refractory rectovaginal and rectoperineal fistula, congenital inguinal hernia, and ASD type 2. Whole exome sequencing was performed for both cases and revealed two novel homozygous missense mutations in G6PC3 that were predicted to be deleterious; c.337G>A, p. Gly113Arg in the first case and c.479C>T; P. Ser160Leu in the second case. To our knowledge, both of these two mutations has not been reported in the G6PDC3 gene. Conclusions: In patients with severe neutropenia with varying extra hematopoietic syndrome, mutation of G6PC3 should be suspected after ruling out other mutations related to neutropenia. This study pointed toward novel G6PC3 mutations, that should be considered in order to diagnose patients with severe congenital neutropenia.