Increased serum levels of granulocyte colony-stimulating factor in patients with severe congenital neutropenia.

Severe congenital neutropenia (SCN), also known as Kostmann Syndrome, is characterized by a maturation arrest of myelopoiesis at the level of promyelocytes with absence of neutrophils in bone marrow (BM) and blood. Hypotheses of the pathophysiology of SCN include (1) defective production of granulocyte colony-stimulating factor (G-CSF), and/or (2) defective response to G-CSF. To exclude defective G-CSF production we tested sera from patients with SCN for the presence of G-CSF using Western blot analysis and NFS-60 proliferation assay. Using these assays we were able to detect increased G-CSF serum levels in SCN patients (150 to 910 pg/mL) as compared with normal controls (between undetectable and 100 pg/mL). These results suggest that patients with SCN have no defect in G-CSF production but a defective response of neutrophil precursors to endogenous G-CSF.