Serum Level of KL-6 as a Marker of Interstitial Lung Disease in Patients with Juvenile Systemic Sclerosis

Objective. Serum KL-6 has been found to be elevated in diseases characterized by diffuse interstitial lung involvement. The purpose of this study was to evaluate serum KL-6 as a marker of interstitial lung disease (ILD) in patients' with juvenile systemic sclerosis (JSS). Methods. Serum concentrations of KL-6 were measured with an immunoassay in 39 serum samples from 12 children with diffuse cutaneous form of JSS (6 patients with and 6 patients without ILD) and from 20 healthy controls comparable for age. In patients sampled serially, the relationship of KL-6 concentrations with the severity of ILD and its response to treatment were evaluated. Results. Serum concentrations of KL-6 were significantly higher in patients with ILD (1687 ± 979 IU/ml) than in patients without (345 ± 95 IU/ml, p <0.01) and healthy controls (311 ± 114 IU/ml, p <0.001). Serum KL-6 concentrations of patients without ILD were not statistically different from those of healthy controls. We found a significant correlation of serum KL-6 concentrations with vital capacity and with diffusing capacity for carbon monoxide (DLCO). Analysis of individual patients showed that serum concentrations of KL-6 were correlated with ILD severity and its response to treatment. Conclusion. Measurement of serum KL-6 concentration is a useful noninvasive marker of pulmonary fibrosis in children with JSS. Its advantages over conventional methods of ILD assessment, such as pulmonary function test and high-resolution computerized tomography, are that it is easy to quantify and to measure repeatedly and it does not need children's cooperation.