Neutrophil marrow cellularity in neutropenia.

In order to identify individuals in whom marrow abnormalities might be contributing to or responsible for neutropenia, we quantitatively examined the number and distribution of cells comprising neutrophil marrow in patients with blood neutrophils less than 2,000/microliter. Neutrophil marrow cellularity was determined from ferrokinetic estimation of normoblast numbers and neutrophil-normoblast ratios obtained from marrow biopsy sections. Only two of 30 patients exhibited the change in cellularity expected of a normal marrow responding to removal of circulating neutrophils: reduced numbers of segmented cells, an expanded mitotic pool, and a normal ratio of metamyelocytes and band forms to promyelocytes and myelocytes. Twenty-three patients had basal mitotic pool size or increased numbers of segmented marrow cells despite neutropenia, a hypoplastic mitotic pool, or a reduction in the number of metas and bands relative to promyelocytes and myelocytes. The results in individual patients were consistent with hypoplasia, subnormal proliferative or release responses, loss of cells during ontogeny, or combinations thereof. In five cases the results could not be so classified. Clinical observations seldom predicted marrow cellularity. Diverse disorders of marrow function appear to be common among neutropenic patients. Neutropenia constitutes a rich field for study of neutrophil marrow physiology.