Serum granulocyte colony-stimulating factor levels in chronic neutropenia of infancy.

Eight infants with chronic neutropenia ranging in age from 1 to 13 months were studied for serum granulocyte colony-stimulating factor (G-CSF) levels. Serum G-CSF levels were elevated, especially when peripheral blood absolute neutrophil counts (ANC) were under 500/microliter in seven patients with autoimmune neutropenia. On the other hand, in a patient with congenital agranulocytosis (Kostmann type), G-CSF levels were below the sensitivity of the assay (less than 50 pg/ml) despite severe neutropenia (less than 100/microliter).