Correlation between rheumatoid factor and peripheral eosinophil count in chronic eosinophilic pneumonia

:  The relationship between the blood level of rheumatoid factor (RF) and the peripheral blood eosinophil (Eo) count (white blood cells × %Eo, Eo count) in a patient diagnosed with chronic eosinophilic pneumonia was evaluated from before the onset till resolution of the disease. RF levels correlated with Eo counts, and showed a strong correlation with the logarithmic value of the Eo counts (r = 0.816). RF levels tended to become elevated earlier and decline later than Eo counts or abnormal X-ray shadows. We concluded that the RF level may reflect the activity of this disease. The mechanism of RF elevation in eosinophil-activated disorders needs to be clarified.