REDUCED SERUM CREATINE-KINASE ACTIVITY IN INFLAMMATORY RHEUMATIC DISEASES

Objective. To determine if serum CK activity is reduced in inflammator y rheumatic diseases and to evaluate whether this phenomenon is linked to disease activity or steroid therapy. Methods. Serum CK activity wa s measured in patients with systemic lupus erythematosus (SLE, n = 52) , rheumatoid arthritis (RA, n = 80), ankylosing spondylitis (AS, n = 8 2), spondyloarthropathies other than AS (SpA, n = 22), and a miscellan eous group (MI, n = 27), and in 103 control patients with noninflammat ory arthropathies (NIA). Laboratory variables of inflammatory activity such as ESR, CRP, platelet count, and hemoglobin (and anti-DNA antibo dies and complement levels in SLE) were measured at the same time. Dai ly dose of steroids was also evaluated. Results. Serum CK activity was significantly reduced in SLE (mean +/- SD: 49 +/- 41 IU/l), RA (68 +/ - 41 IU/l), SpA (88 +/- 53 IU/l), and MI (75 +/- 32 IU/l)) compared to controls (111 +/- 38 IU/l) (p = 0.002 for SpA and p < 0.001 for the o ther groups). No differences in CK values were observed between AS and controls, although AS patients with peripheral arthritis had lower se rum CK activity than those without (80 +/- 32 vs 121 +/- 62 IU/l, resp ectively, p < 0.05. ESR, CRP, and platelets correlated inversely with CK values in RA, AS, and MI. In the SpA group only ESR correlated inve rsely with CK. In SLE, a positive correlation was found between CK val ues and CH50 and a negative one with anti-DNA levels. Patients taking steroids had significantly lower CK activity than those without cortic otherapy. However, multivariate analysis showed that only inflammatory activity and no steroids had an effect in reducing CK activity. Concl usion. Serum CK activity is significantly reduced in several inflammat ory rheumatic diseases. Inflammatory activity seems to play the major role in this phenomenon.