Abstract
BACKGROUND: Kikuchi-Fujimoto disease (KFD) is a rare condition characterized by elevated serum ferritin levels and a robust immune response involving various lymphocyte subtypes. However, the relationship between ferritin and lymphocyte subtypes remains unexplored. This study aims to offer insights into the immune response in KFD. METHODS: Sixty-five hospitalized patients diagnosed with KFD through histopathological examination were categorized into hyperferritinemia and control groups. Baseline characteristics, ultrasound findings, and laboratory results were retrospectively collected for analysis. RESULTS: Biopsied lymph nodes in KFD patients were predominantly located in the neck (89.2%), followed by the axilla (6.2%) and submandible (4.6%). These nodes exhibited a mean long diameter of 2.3 mm (interquartile range [IQR] 2.0-2.8 mm) and a mean short diameter of 0.9 mm (IQR 0.7-1.2 mm). A comparison between the hyperferritinemia and control groups revealed significant differences: Serum ferritin levels were 664.4 µg/L (IQR 450.5-963.9 µg/L) vs. 111.3 µg/L (IQR 75.7-207.4 µg/L), respectively. Additionally, counts of CD3+ and CD4+ lymphocytes, as well as NK cells, were reduced in the hyperferritinemia group: CD4+ lymphocyte counts were 387.7 cells/µL (IQR 261.5-479.7 cells/µL) vs. 479.9 cells/µL (IQR 396.2-662.0 cells/µL), p = 0.021; and the percentage of CD4+ lymphocytes was 33.8% (IQR 29.4-41.7%) vs. 42.4% (IQR 40.4-48.6%), p = 0.000. Furthermore, serum ferritin levels exhibited a linear positive correlation with CRP (r = 0.420, p = 0.001) and a negative correlation with CD4+ lymphocyte count (r = -0.412, p = 0.007) and percentage of CD4+ lymphocytes (r = -0.567, p = 0.000). CONCLUSIONS: Patients with KFD demonstrated immunosuppression characterized by decreased counts of circulating CD3+ and CD4+ lymphocytes, as well as NK cells. Moreover, serum ferritin levels were inversely correlated with CD4+ lymphocyte counts, suggesting a potential role of ferritin in immune dysregulation in KFD.