Increased Expression of CD169 on Monocytes in Adult-Onset Kikuchi–Fujimoto Disease

Kikuchi–Fujimoto disease (KFD) is a rare, benign lymphoproliferative disease of uncertain origin that can mimic other inflammatory or clonal lymphoproliferative disorders. Given the lack of available blood biomarkers, diagnosis is based on the biopsy of an affected lymph node. In recent years, evidence has been mounting that a dysregulated type I INF innate immune response plays a pivotal role in the pathogenesis of the disease and might be a future therapeutic target. Nonetheless, laboratory assays measuring the expression of interferon alpha (INFα) and INF-stimulated genes (ISGs) are cumbersome and not widely available, limiting their use in clinical and translational research and encouraging the use of more convenient surrogate markers. In this study, a rapid flow cytometry assay detected increased levels of expression of CD169 (Siglec-1), an INFα-induced surface protein involved in innate immunity regulation, on circulating monocytes from two patients with KFD. Our results are in line with previous experiences and set the stage for a more extended investigation into the use of this assay in exploring the pathophysiology of KFD.