CRP and arthritic joint disease: CRP is considered a standard marker of the inflammatory process, and its synthesis is regulated by IL-6.52 As is known, CRP increases in persons with an active course of SLE.53 54 Thus, according to the literature, in patients with SLE, an increase in CRP is associated with active serositis, arthritis or myositis.55 Thus, the negative association of vitamin D content with an increase in CRP may be an additional indication of the influence of an active inflammatory process.