SCN (severe congenital neutropenia): An condition characterized by a lack of neutrophils, a type of white blood cell that is important in fighting infection. It is usually, but not always, hereditary Children with severe congenital neutropenia (SCN) suffer frequent infections from bacteria, which in the past led to death in three-quarters of cases before three years of age. Children with SCN have no special problems with viral or fungal infections, but they do have an increased risk of developing acute myelogenous leukemia or myelodysplasia, a bone marrow disorder. Aside from agranulocytosis, the bone marrow and blood show a number of other abnormalities, and the gamma globulin level in blood is low.

Hereditary SCN is an autosomal recessive disorder, so both parents must carry an SCN gene to transmit the disease. Each child of two parents with the SCN gene has a 25 percent risk of receiving both SCN genes and therefore the disease.

Treatment with recombinant human granulocyte colony-stimulating factor (GCSF) elevates the granulocyte counts, helps resolve preexisting infections, diminishes the number of new infections and results in significant improvements in survival and quality of life. Some patients have developed leukemia or myelodysplastic syndrome following treatment with GCSF, however.

Also known as Kostmann's disease or syndrome, infantile genetic agranulocytosis, genetic infantile agranulocytosis.