Increased frequency of monoclonal gammopathy of undetermined significance in patients with nonimmune chronic idiopathic neutropenia syndrome

This study describes the frequency of monoclonal gammopathy of undetermined significance (MGUS) and the changes in some inflammation-related serum pro teins in 157 patients with nonimmune chronic idiopathic neutropenia syndrom e (NICINS). Of these patients, 42 had pronounced neutropenia with neutrophi l counts < 1500/muL, and 115 had mild neutropenia with neutrophil counts ra nging from 1500 to 2499/muL. Sixty-six volunteers served as health!: contro l subjects and 157 age- and sex-matched patients hospitalized for nonmalign ant diseases served as patient control subjects. We found that 28.6% of pat ients with pronounced neutropenia and 14.8% of patients with mild neutropen ia had increased serum gamma globulins (above the 95% confidence limit of v alues of the control subjects). In the group of patients with pronounced ne utropenia, 30.9% had increased immunoglobulin (Ig)G values and 23.8% had in creased IgA values. In the group of patients with mild neutropenia. 17.4% h ad increased IgG values and 21.7% had increased IgA values. IgG and IgA val ues strongly correlated with the neutrophil count. No changes in serum IgM were found. Three of 42 patients with pronounced neutropenia (7.14%) and 3 of 115 patients with mild neutropenia (2.61%) had serum immunofixation test s which showed a small monoclonal spike-4 were IgG-kappa type. 1 was IgG-la mbda type, and 1 was IgA-kappa type. None of the healthy or patient control subjects had any evidence of MGUS. No significant changes in the amount of monoclonal spikes were documented during an 18- to 143-month follow-up (me dian, 58 months). Except for significantly increased alpha (1)-antitrypsin levels, there were no significant differences in the levels of acute-phase proteins studied between the study patients and the control subjects. These findings are consistent with our previous report suggesting the possible e xistence of an unrecognized low-grade chronic inflammation in patients with NICINS, which may be involved in the pathogenesis of neutropenia in the af fected subjects. (C) 2001 The Japanese Society of Hematology.