Vitamin D binding protein isoforms as candidate predictors of disease extension in childhood arthritis

Introduction. Juvenile idiopathic arthritis (JIA) comprises a poorly understood group ofchronic autoimmune diseases with variable clinical outcomes. We investigated whetherthe synovial fluid (SF) proteome could distinguish a subset of patients in whom diseaseextends to affect a large number of joints.Methods. SF samples from 57 patients were obtained around time of initial diagnosis of JIA,labeled with Cy dyes and separated by two-dimensional electrophoresis. Multivariateanalyses were used to isolate a panel of proteins which distinguish patient subgroups.Proteins were identified using MALDI-TOF mass spectrometry with expression verified byimmunochemical methods. Protein glycosylation status was confirmed by hydrophilicinteraction liquid chromatography.Results. A truncated isoform of vitamin D binding protein (VDBP) is present at significantlyreduced levels in the SF of oligoarticular patients at risk of disease extension, relative toother subgroups (p