Severe congenital neutropenia.

Congenital neutropenia (CN) is a genetically heterogeneous bone marrow failure syndrome characterized by a maturation arrest of myelopoiesis at the level of the promyelocyte/myelocyte stage with peripheral blood absolute neutrophil counts below 0.5 x 10(9)/L. From early infancy patients who have CN suffer from bacterial infections. Leukemias occur in both the autosomal dominant and recessive subtypes of CN. The individual risk for each genetic subtype needs to be evaluated further, because the number of patients tested for the underlying genetic defect is still limited. Acquired G-CSFR (CSF3R) mutations are detected in approximately 80% of patients who had CN and who developed acute myeloid leukemia, suggesting that these mutations are involved in leukemogenesis.