Procalcitonin Levels in Patients with Juvenile Idiopathic Inflammatory Myopathies

Background: Patients with juvenile idiopathic inflammatory myopathies (JIIMs) are at an increased risk of infection due to immunosuppression. Serum procalcitonin (PCT) is a biomarker for diagnosing bacterial infections. While no substantial studies have examined PCT in JIIM, it is slightly elevated in Still’s disease. Objectives: We aimed to investigate whether PCT is elevated in active JIIM in the absence of bacterial infection. We conducted a cross-sectional study of 42 newly diagnosed JIIM patients, including 18 treatment-naïve individuals, and 21 healthy controls. Clinical assessments included disease activity scores (Total Disease Activity Score [DAS-T], Skin Disease Activity Score [DAS-S], Muscle Disease Activity Score [DAS-M]), and muscle strength (Childhood Myositis Assessment Scale). Laboratory evaluations covered muscle enzymes and inflammatory markers. Only five JIIM patients had detectable PCT levels (maximum 0.39 ng/mL), while all controls had undetectable levels. Median PCT levels did not significantly differ between JIIM patients and controls ( P = 0.16). Elevated neopterin showed a positive correlation with muscle weakness (DAS-M, r = 0.53, P = 0.002) and skin rash (DAS-S, r = 0.434, P = 0.012). All muscle enzymes correlated positively with DAS-M. Conclusion: Most children with active JIIM had undetectable PCT levels. These findings suggest that moderate to high PCT elevations in JIIM patients are more likely due to infection than disease activity.