People with systemic sclerosis who also have lung disease have much lower levels of the natural peptide LL‑37 in their blood. The study suggests LL‑37 might be linked to lung problems, but it doesn't show how to use this information for treatment or prevention.

Interstitial lung disease (ILD) is the leading cause of systemic sclerosis (SSc) related morbidity and mortality. LL-37 peptide is the only cathelicidin of the human antimicrobial peptide family with antimicrobial effects and immunomodulatory activity. LL-37 has anti-fibrotic effects and anti-apoptotic effects on SSc dermal fibroblasts. The aim of the study was to investigate the circulating levels of LL-37 in SSc patients and its association with clinical, laboratory, and instrumental parameters. Fifty-eight SSc patients (30 with and 28 without pulmonary involvement) and 28 healthy controls were enrolled in the study. Pulmonary involvement was defined when ILD was found at HRCT (ground glass, reticular, and honeycombing pattern). Circulating LL-37 levels were measured with ELISA test. In SSc patients with ILD serum, LL-37 concentrations were remarkably lower (1.36 mg/ml) than those in SSc patients without ILD (4.62 ng/ml, p = 0.035) and controls (5.53 ng/ml, p = 0.009). In SSc patients without ILD, serum LL-37 levels were not different from controls (p = 0.812). No significant association or correlation was found between LL-37 levels and any other clinical, serological, or instrumental features. Serum LL-37 levels are significantly lower in patients with SSc ILD. Our results may suggest that lower LL-37 levels may be associated with the development of ILD. Whether circulating levels of LL-37 might be used as an indirect marker of ILD remains to be determined in larger SSc cohorts.