Morphologically defined myeloid cell compartments, lymphocyte subpopulations, and histological findings of bone marrow in patients with nonimmune chronic idiopathic neutropenia of adults

P <0.001 and P<0.001, respectively). Individual proportions of these cells strongly correlated with the number of circulating neutrophils (r=−0.462, P<0.01 and r=0.495, P<0.01, respectively). However, in the great majority of patients (78.9%), no significant changes in marrow cellularity or the myeloid to erythroid cell ratio could be demonstrated. Patients also had increased proportions of CD19⁺B cells, CD20⁺B cells, and plasma cells with polytypic expression relative to controls (P<0.02, P<0.01, and P<0.001, respectively). Individual values of plasma cells were inversely correlated with the number of blood neutrophils (r=−0.414, P<0.01). Dispersed bcl-2⁺lymphocytic aggregates without germinal centers were seen in about one-third of the patients. T cells and natural killer (NK) cells did not show any significant change. Patients had increased proportions of CD57⁺, CD16⁺, and HLA-DR⁺ cells and, in a few cases, increased proportions of histiocytes and eosinophils. CD45RO⁺ cells were reduced only in patients with pronounced neutropenia. Expression of p53 protein has not been detected in any cell population. With the exception of some megaloblastoid features of erythroid lineage seen in two patients and the presence of some micromegacaryocytes seen in two others, no significant morphological abnormalities were noted. All of these findings are consistent with our previously reported suggestion for the possible existence of an underlying low-grade chronic inflammatory process in NI-CINA patients, which may be involved in the pathogenesis of neutropenia in the affected subjects. Received: 8 February 2000 / Accepted: 7 April 2000