Serum calprotectin: review of its usefulness and validity in paediatric rheumatic diseases.

In most childhood rheumatic diseases, specific diagnostic markers are not yet available. Therefore, a major emphasis in medical research today is directed to the discovery of new inflammation molecules, like calprotectin. Calprotectin (MRP8/MRP14) is a complex of calcium- and zinc-binding proteins that belong to the S100 protein family. This protein is directly released by leukocytes during the interaction with inflammatory activated endothelium at the site of inflammation. Increased plasma calprotectin levels have been found in inflammatory chronic diseases such as rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), inflammatory bowel diseases (IBD), multiple sclerosis, cystic fibrosis and systemic lupus erythematosus (SLE). In these diseases, serum calprotectin has been shown to correlate with disease activity and laboratory variables of inflammation such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). This review outlines the validity and the possible applications of calprotectin as a new inflammation marker in paediatric rheumatic diseases.