ab2006

Low values of creatine kinase in systemic lupus erythematosus. Clinical significance in 300 patients

J. Font¹, M. Ramos-Casals¹, A.P. Vilas², M. García-Carrasco^1,3, M.-P. Brito³, G. de la Red¹, V. Gil1, A. García-Carrasco¹, R. Cervera¹, M. Ingelmo¹

¹Department of Autoimmune Diseases and ²Department of Internal Medicine, Hospital de Egas Moniz, Lisbon, Portugal; and ³Department of Rheumatology, Benemérita Universidad Autónoma de Puebla, Puebla, México.

ABSTRACT
Objective
To study creatine kinase (CK) activity in a large series of patients with systemic lupus erythematosus (SLE) and identify the clinical and immunological features related to reduced levels.

Methods
In a cross-sectional study, serum CK activity was measured in 300 consecutive patients with SLE (271 females and 29 males, with a mean age of 36 years). All patients fulfilled the 1982 revised criteria of the American College of Rheumatology.

Results
Low serum CK levels (< 33 IU/L) were detected in 118 (39%) of SLE patients. When compared to SLE patients with normal serum CK levels, those with SLE and low serum CK levels had a higher frequency of fever (53% vs. 34%, p =0.017), renal involvement (43% vs. 27%, p = 0.004), and hemolytic anemia (13% vs. 6%, p = 0.037). In addition, SLE patients with low CK values also presented lower values of hemoglobin, total proteins, albumin, cholesterol and triglycerides, higher values of ESR and low C3 (44% vs. 27%, p = 0.004), C4 (57% vs. 37%, p = 0.001) and CH50 levels (60% vs. 41%, p = 0.02). We analysed in 69 patients the correlation between CK and 24-hour proteinuria values, and found that those with a 24-hour proteinuria > 1500 mg/day showed lower CK values than those with proteinuria < 1500 (31.95 vs 63.84 IU/L, p=0.046).

Conclusion
We observed that serum CK levels were reduced in 39% of SLE patients. Reduced serum CK activity was significantly related to some clinical (fever, nephropathy), hematological (high ESR, hemolytic anemia) and immunological (hypocomplementemia) features, which relate to disease activity. This suggest that reduced CK activity might be inversely correlated to inflammatory activity in SLE.

Key words
Systemic lupus erythematosus, creatine kinase.

Please address correspondence to: Dr. Josep Font, Servei de Malalties Autoinmunes, Hospital Clínic, C/ Villarroel no. 170, 08036-Barcelona, Spain.
E-mail: jfont@clinic.ub.es