Serum thrombomodulin in systemic lupus erythematosus and juvenile idiopathic arthritis.

Thrombomodulin is a thrombin receptor on the vascular endothelial cell surface which is likely released upon endothelial cell damage. Serum soluble thrombomodulin (sTM) was assessed and investigated as a parameter of disease activity in children and adolescents with systemic lupus erythematosus (SLE) and juvenile idiopathic arthritis (JIA). Patients included in this study were regularly attending the Allergy and Immunology Clinic, Children's Hospital, Ain Shams University. They were 38 (76%) females and 12 (24%) males, their ages ranged between 5 and 18 years with a mean of 14.3 +/- 4.84 years and median of 13 years. They were divided into two groups: SLE group which included 20 patients and JIA group which included 30 patients; and the control group which included 30 healthy age and sex-matched individuals for comparison. Disease activity in SLE patients was evaluated by systemic lupus erythematosus disease activity index (SLEDAI) score, while in JIA patients disease activity was determined by number of joints with active arthritis, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Serum levels of sTM were determined by enzyme-linked immunosorbent (ELISA) assay. Serum levels of sTM were significantly higher in SLE and JIA patients in comparison with the control group; there was no significant difference between SLE and JIA patients. In SLE patients, a highly significant correlation was found between sTM and SLEDAI score (r = 0.99, p < 0.001). In JIA patients, a highly significant correlation was found between sTM and number of joints with active arthritis as well as ESR (r = 0.85, p < 0.001; r = 0.93, p < 0.001, respectively). Levels of sTM were significantly higher in CRP-positive than CRP-negative JIA patients. Serum sTM is a useful serologic marker of disease activity in SLE and JIA. It may prove to be a potential indicator for early and more aggressive treatment. Furthermore, sTM may prove to be an important marker for vasculitis in general.