[Association of markers of rheumatoid arthritis in lupus. Is it a rhupus?]

Abstract

Anti-citrullinated cyclic peptide antibodies (ACPA) were initially considered very specific for the diagnosis of rheumatoid arthritis (RA), and can predict the prognosis of the disease. However, these antibodies can be detected in other autoimmune diseases, including systemic lupus erythematosus (SLE), the most common manifestation of which is inflammatory arthritis, which is often found in early-stage rheumatoid arthritis. The aim of our study is to evaluate the prevalence of ACPA antibodies and to analyze the profiles of their associations with autoantibodies specific to lupus, in order to look for a possible rhupus overlap syndrome in our patients. This is a retrospective study, carried out at the immunology unit, at Blida University Hospital, Algeria, involving 96 lupus patients, diagnosed according to the criteria of the American college of rheumatology (ACR). ACPA have been identified by the ELISA technique. ACPA was positive in 14,56% of our patients, whereas anti-DNA, anti-Sm and rheumatoid factor (RF) autoantibodies were positive, respectively in 47.09%, 35.41%, and in 26.04% of our patients. In addition, the presence of ACPA with anti DNA was found in 12.5% of patients. Of the 14 with ACPA+, 57.14% had arthritis. Our results confirm that ACPA auto-antibodies do not represent a pathognomonic criterion of RA. This sometimes makes the differential diagnosis with lupus difficult especially at the beginning of the disease.

Keywords: ACPA; SLE; anti-DNA; anti-Sm; rhupus.