VTN and systemic lupus erythematosus: On the other hand, in the study by Gundogdu et al. [39], serum levels of VTN were found to be lower in the SSc group compared to patients with SLE or healthy controls, suggesting the accumulation of VTN in fibrotic skin and subcutaneous tissues as a cause, which has already been demonstrated in experimental models of renal fibrosis [40].