Serum Alkaline Phosphatase Levels in Pediatric Kikuchi-Fujimoto Disease: A Retrospective Observational Analysis.

Aim: Kikuchi-Fujimoto disease (KFD) rarely affects pediatric patients and is characterized by prolonged fever and cervical lymphadenopathy. The diagnosis of KFD remains challenging and often requires an invasive biopsy. Low serum alkaline phosphatase levels have frequently been observed in patients with KFD; however, the clinical significance of low serum alkaline phosphatase levels remains unclear.

Methods: This retrospective study included pediatric patients aged < 16 years who were pathologically or clinically diagnosed with KFD and infectious mononucleosis between April 2016 and March 2023. Serum alkaline phosphatase levels were analyzed employing age- and sex-specific reference intervals. Clinical and laboratory data were evaluated to determine their association with serum alkaline phosphatase levels.

Results: Thirty patients with KFD and 23 patients with infectious mononucleosis were included in the study. Seventeen patients with KFD (56.7%) had serum alkaline phosphatase levels below the 2.5th percentile of the age- and sex-specific reference intervals. Serum alkaline phosphatase levels were significantly lower in patients with KFD than in those with infectious mononucleosis. Clinical and other laboratory findings were not significantly different between patients with KFD with or without a decline in serum alkaline phosphatase levels.

Conclusion: A decrease in serum alkaline phosphatase levels, particularly when assessed as a percentage of age- and sex-specific reference intervals, may be a valuable and noninvasive supportive feature of KFD in pediatric patients.