Circulating LL-37 is a biomarker for eczema severity in children.

BACKGROUND: Eczema lesions are characterized by impaired expression of antimicrobial peptides such as cathelicidin, which play crucial roles in the innate immune defence against cutaneous infections. LL-37 corresponds to amino acids 134-170 of human cathelicidin and is a multifunctional host defence molecule essential for normal immune responses to infection and tissue injury. OBJECTIVES: The aim of this study was to investigate the relationship between childhood eczema and circulating LL-37 levels. METHODS: One hundred and forty-four eczema children and 36 controls were recruited. Eczema severity was assessed by SCORing Atopic Dermatitis (SCORAD) and serum LL-37 concentration measured using enzyme immunoassay. Patients' skin hydration and transepidermal water loss at forearms were measured using Corneometer and Tewameter. RESULTS: Patients' mean SCORAD was 49.2 and their disease was classified as mild (n=28; 12.8%), moderate (n=95; 43.6%) and severe (n=95; 43.6%). Serum LL-37 concentrations did not differ between eczema patients and controls (mean: 832 pg/mL vs. 952 pg/mL, P=0.471). However, serum LL-37 concentrations increased with increasing eczema severity among the patients (P=0.005 for trend). This biomarker shows weakly positive correlation with patients' objective SCORAD (r=0.207, P=0.013) and age (r=0.170, P=0.041), but not skin hydration or transepidermal water loss (P>0.09). Linear regression confirmed significant association between objective SCORAD and serum LL-37 when adjusted for age and gender as covariates (β=0.171, P=0.038). On the other hand, serum LL-37 did not differ between patients with and without heavy growth of staphylococci (P=0.151). CONCLUSIONS: Circulating LL-37 may be a biomarker for severity of childhood eczema, which supports the importance of innate immunity in eczema pathogenesis.