Antiphospholipid antibodies and kidney involvement in patients with systemic sclerosis

Antiphospholipid (aPL) antibodies are often detected in systemic autoimmune diseases. The aim of the study was to examine the correlation between the presence of aPL and certain markers of renal function in systemic sclerosis (SSc). Fifty patients (pts) with SSc were examined for the presence of antibodies to cardiolipin (aCL) and to anti-beta 2 glycoprotein I (a-B2GPI) in immunoglobulin M (IgM) and IgG class. Moreover, serum levels of creatinine, cystatin C, and glomerular filtration rate (GFR) were determined in all patients. In all studied pts together, three multiple-regression analyses were performed with one set cystatin C as a dependent variable, in the second GFR according to the Cockcroft–Gault formula and in the third creatinine clearance by Modification of Diet in Renal Disease (MDRD) formula. As independent variables, aPL of either type were inserted in addition to disease duration and age. IgG aCL was significantly positively associated with serum cystatin C (p = 0.002), significantly negatively associated with creatinine clearance according to the Cockcroft–Gault and MDRD formula (p = 0.01 and 0.02, respectively). IgG a-B2GPI was significantly negatively associated with creatinine clearance according to the Cockcroft–Gault (p = 0.03) and MDRD (p = 0.01) formula. IgM aCL and IgM a-B2GPI were not associated with any markers of the renal function. Our study suggests the relationship between kidney involvement and the positivity for some aPL in patients with SSc. Positivity for IgG aCL and IgG a-B2GPI in patients with SSc without secondary antiphospholipid syndrome seems to be connected with decrease of glomerular filtration.