Clinical significance of antinuclear antibodies in patients with Kikuchi‐Fujimoto disease: A retrospective cohort study

Background The clinical significance of antinuclear antibodies (ANA) in Kikuchi‐Fujimoto disease (KFD) remains unclear, particularly whether ANA positivity predicts progression to autoimmune diseases. This study aimed to investigate the association of ANA with clinical features and prognosis in patients with KFD. Methods This retrospective cohort study included KFD patients confirmed by lymph node biopsy at Beijing Friendship Hospital, Capital Medical University, from January 2015 to January 2025. Patients were categorized into ANA‐positive and ANA‐negative groups. Clinical characteristics, laboratory parameters, treatment, and outcomes were compared. Results A total of 140 KFD patients were included. Only 10 patients (7.1%) had concurrent rheumatic diseases at presentation. Among the remaining 130 patients without rheumatic diseases, ANA positivity was 60.0% (78/130). Other autoantibodies (including anti‐Sm, anti‐SSA, and anti‐ribosomal P protein) were detected in 9 ANA‐positive patients (11.5%), with none in the ANA‐negative group ( p < 0.001). The ANA‐negative group had a significantly higher proportion of female patients (58.5% vs. 37.9%, p = 0.028), while lactate levels were slightly lower in the ANA‐positive group (median 1.8 vs. 1.9 mmol/L, p = 0.028). Among the 130 KFD patients without concurrent rheumatic diseases, 107 patients (82.3%) completed follow‐up (median 39 months). During follow‐up, six relapses (5.6%) occurred, with no significant difference between ANA‐positive and ANA‐negative groups (5.9% vs. 5.1%, p = 1.000). Repeat ANA testing was performed in only 15 patients (all in the ANA‐positive group), of whom 11 (73.3%) seroconverted to negative. During follow‐up, one ANA‐positive patient was diagnosed with rheumatoid arthritis after 7 years, and another was diagnosed with ankylosing spondylitis after 9 years. No patient developed systemic lupus erythematosus or other connective tissue diseases. Conclusions ANA positivity is common in KFD but does not necessarily indicate underlying rheumatic disease or predict progression to overt autoimmune disease. Most patients have favorable outcomes, and the short‐term risk of developing connective tissue diseases is low. Longer follow‐up is warranted.