Prevalence of peripheral eosinophilia and clinical associations in systemic sclerosis patients

Peripheral eosinophilia (eosinophilia) is observed among systemic sclerosis (SSc) patients. The association between eosinophilia and SSc in terms of pathogenesis remains uncertain. We aimed to determine the prevalence of the clinical, serological, and cytokine associations with eosinophilia in SSc patients.

A cross-sectional study was conducted among adult SSc patients. We excluded patients having overlap syndrome and other conditions that cause eosinophilia. Investigations into the etiology of eosinophilia were performed on the same study date, including clinical parameters, blood tests for tissue parasites, IgE, interleukin-5, and transforming growth factor-beta. Eosinophilia is defined when the total eosinophil count is > 500 cells/mm³.

According to the sample size calculation, 185 patients were enrolled, of whom 57 (30.8%) had eosinophilia. The causes of eosinophilia were based on laboratory indicators without clinical symptoms in 21 cases (10 had a parasitic infection, 9 adrenal insufficiency, and 2 tuberculosis). After excluding suspected causes of eosinophilia, the total prevalence of eosinophilia was 21.9% (95%CI 15.9-29.1). Most of patients (164 cases; 70.6%) had diffuse cutaneous SSc. According to the logistic regression analysis, the factors associated with eosinophilia were being male (OR 3.46), duration of disease increasing every year (OR 1.16), and Raynaud's phenomenon (OR 0.27), while SSc subset, serology (i.e., anti-topoisomerase I, anti-neutrophilic cytoplasmic antibody), inflammatory markers, and cytokine levels were not.

Eosinophilia of unknown causes was detected in 1 in 5 SSc patients, particularly in males with no vasculopathy. Eosinophilia has a nonspecific role vis-à-vis clinical relevance in SSc.