Active ulcers at presentation 21 (14.3)

indicate vascular involvement in systemic sclerosis Interleukin 33 (IL-33) belongs to the IL-1 family and was found in smooth muscle cells, epithelial cells, fibroblasts, keratinocytes, endothelial cells, dendritic cells and activated macrophages.1 IL-33 binds the orphan receptor ST2 and induces gene expression of Th2-associated cytokines. Treatment of wild-type mice with IL-33 led to changes in vessels, digestive tract and lungs.2 Manetti et al3 recently investigated serum IL-33 levels by means of an ELISA in 58 patients with systemic sclerosis (SSc) and 30 healthy individuals. They observed that serum IL-33 was significantly increased in patients with SSc as compared with healthy controls. They also found that serum IL-33 levels were associated with early disease stage and microvascular involvement as determined by capillaroscopy. The study of Manetti et al3 prompted us to investigate serum IL-33 levels in a larger sample of German SSc patients and controls