| Note | Severe chronic neutropenia (SCN) is a heterogeneous group of disorders characterized by chronic neutropenia and serious recurrent infections. The defining characteristic of all of these diseases is the presence of severe neutropenia with absolute neutrophil counts of less than 0.5X109 /L on three separate occasions over a six week period. Some clinically distinctive cases, known as cyclic neutropenia show oscillation in neutrophil levels with a periodicity of approximately 21 days. SCN is distinguished from Shwatchman-Diamond Syndrome by the absence of exocrine pancreas deficiency and growth retardation. |
| Phenotype and clinics | Phenotype stem cell origin: Constitutional disorder affecting myeloid lineage cells Epidemiology: The disease is most common in causcasians and presents in childhood. Clinical features: Congenital neutropenia usually presents in early childhood and is slightly more common in males. Cyclic forms are slightly more common in females.SCN patients develop frequent fevers, skin infections and stomatitis with organisms such as E. coli, S. aureus, and Pseudomonas species. 90% of patients are diagnosed by 6 months of age. Patients tend to develop hematological malignancies (see below) Pathology: The absolute neutrophil count is usually less than 0.2X109 /L. The bone marrow of affected patients shows an arrest in maturation at the promyelocyte stage, often with a monocytosis and sometimes with eosinophilia. The peripheral blood shows a paucity of neutrophils and often monocytosis and eosinophilia. |
| Neoplastic risk | Roughly 50% of patients present with myelodysplastic syndromes (MDS), another 10% with therapy associated MDS, 25% with de novo acute myeloid leukemia (AML), and the remainder with a range of other myeloproliferative disorders. The majority of MDS patients transform into AML with a short preleukemic phase. |
| Treatment | More than 90% of patients respond to G-CSF therapy, which may result in cyclic oscillations in neutrophil count. G-CSF therapy may be complicated by significant bone loss and the development of AML. Hematopoietic stem cell transplantation has shown promise in the treatment of non-responders. |
| Prognosis | With the advent of G-CSF therapy infectious deaths are rare. Approximately 10% of patients develop AML. This is associated in almost all cases with G-CSF-R mutations. This is not thought to be the direct result of G-CSF therapy but rather an underlying predisposition for the development of myeloid leukemia. Cyclic neutropenia patients do not have an increased risk for development of acute leukemia. |
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