Chronic idiopathic neutropenia: Granulopoietic assessment by both marrow culture and granulocyte kinetics

Granulopoietic assessment was made in 14 patients with chronic idiopathic neutropenia (CIN) whose neutrophils were consistently less than 1.5 × 10⁹/ liter and in whom there was absence of splenomegaly and recent drug ingestion. Granulopoiesis was studied using a combination of bone marrow culture in nutrient agar and granulocyte kinetics. Agar colony growth assessed bone marrow concentration of granulocyte progenitor cells (GPC) and the proportion of GPC in DNA synthesis by in vitro ³HTdR suicide. Granulocyte kinetics with in vitro DF³²P labelling of patient granulocytes measured granulocyte half-life (T^1/2), turnover rate (GTR), and the circulating, marginated, and total blood granulocyte pools. The results indicated that either GPC concentration or the proportion of GPC in DNA synthesis was outside the normal range in all but one patient and decreased in ten out of 14 patients. CIN was also characterized by reduced total, circulating, and marginated blood granulocyte pools, reduced GTR, and normal granulocyte half-life. The neutropenia appeared to be due to a variety of intra-marrow causes, including either a reduction in the GPC compartment, a reduction in GPC proliferation, a maturation arrest, or a reduced amplication during granulopoiesis. Increased granulocyte utilization, intra-vascular destruction or excessive margination could be excluded as possible causes of CIN in this series. Although GPC parameters tended to be reduced, suggesting a production defect, there were signs in nine patients that the bone marrow was attempting to compensate for the peripheral neutropenia. It is suggested that for a complete assessment of granulopoiesis in man, granulocyte kinetic studies need to be combined with quantitative studies of the bone marrow granulocyte progenitor compartment using the agar colony system.