Neutropenia and infections in Felty's syndrome.

Fifteen patients with Felty's syndrome (FS) were studied prospectively during a 3-year period to determine the influence of multiple haematologic parameters on the incidence of infections. An increased risk of recurrent major and minor infections was primarily related to peripheral blood polymorphonuclear cell (PMN) counts of less than 0.1 x 10(9)/l. Bone marrow lymphocytosis, a decreased percentage of PMN in bone marrow differential counts and an impaired in vitro growth of colony-forming unit-PMN macrophage were also related to an increased incidence of infection but were predominantly present in patients with less than 0.1 x 10(9)/l circulating PMN. The maximal response in the number of circulating PMN measured after injection of epinephrine and hydrocortisone varied substantially within patients, but those with less than 0.1 x 10(9)/l PMN always had lower responses than those with greater than 0.1 x 10(9)/l PMN. These variables did not therefore contribute to the identification of FS patients at risk of infection.