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Background and Objectives: The two main complications of severe chronic neutropenia are fatal sepsis and myelodysplasia/acute leukemia (MDS/AL). Granulocyte colony-stimulating factor (G-CSF) therapy has significantly reduced the frequency and severity of infections, but its possible influence on the risk of malignancy is not known., Design and Methods: The French Severe Chronic Neutropenia (SCN) Registry has prospectively collected data since 1994 on 231 patients with various forms of SCN, namely severe congenital neutropenia (n=101), cyclic neutropenia (n=60), glycogen storage disease type Ib (GSDIb) (n=15) and Shwachman-Diamond syndrome (SDS)(n=55). The median overall follow-up is 11.1 years. Parameters of exposure to G-CSF therapy, such as the time averaged dose, follow up after first use of G-CSF, and the cumulative dose, have been recorded., Results: Eight septic deaths occurred, of which 6 among patients with severe congenital neutropenia and 2 in patients with cyclic neutropenia; none of these 8 patients was receiving G-CSF therapy. No septic deaths occurred during G-CSF therapy. Thirteen cases of MDS/AL were recorded. The cumulative incidence of MDS/AL was 2.7% (SD 1.3%) at 10 years and 8.1% (SD 2.7%) at 20 years., Interpretation and Conclusions: Risk factors for MDS/AL were the diagnostic category, the severity of neutropenia, younger age at diagnosis, and strong exposure to G-CSF. MDS/AL only occurred in patients with severe congenital neutropenia and SDS. Owing to their particular susceptibility to infections, patients with severe congenital neutropenia had the strongest exposure to G-CSF; the risk of leukemia increased with the degree of G-CSF exposure in this subgroup.

Heterozygous mutations of the gene encoding neutrophil elastase (ELA2) have been associated with cyclic neutropenia (CN) and severe congenital neutropenia (SCN). To date, 30 different mutations have been reported, but no correlation has been found with the degree of neutropenia. To address this issue, we analyzed the clinical, hematologic, and molecular characteristics of 81 unrelated patients with SCN (n = 54) or CN (n = 27). We identified mutations in 31 patients, two thirds of whom had sporadic forms. Familial cases were consistent with dominant inheritance. Seventeen novel mutations were identified, showing that the mutational spectrum encompasses not only the region encoding the mature enzyme but also the prodomains and promoter region. Genotype-phenotype analysis strongly suggested that ELA2 mutations correlate with more severe expression of neutropenia, specifically in patients diagnosed with SCN. This study underlines the importance of ELA2 molecular screening to identify patients who may be at particular risk of severe bacterial infections and/or acute myeloid leukemia/myelodysplasia. By phenotypic analysis of affected relatives and carriers of the same ELA2 mutations, we showed that the expression of neutropenia in CN and SCN may be either homogeneous or variable according to the type of mutations, suggesting different pathogenetic mechanisms.