Background Hypocomplementemia was previously reported in patients (pts) with rheumatoid arthritis (RA) treated with tocilizumab (TCZ). Decreased complement (C3,C4) production was suggested as a possible mechanism. The long-term consequences concerning serious bacterial infections or autoimmune disorders (AID) have not been reported.
Objectives To assess the long-term outcome of RA pts treated with TCZ who developed hypocomplementemia regarding serious bacterial infections or AID.
Methods The charts of RA pts treated with TCZ at our center were reviewed retrospectively. Data regarding pts' age, gender, disease duration, presence of rheumatoid factor (RF), antibodies to citrullinated peptide (ACPA), and nuclear antigens (ANA), previous and concomitant non-biological DMARDs, previous biological DMARDs, and TCZ treatment duration; laboratory parameters including leucocytes and thrombocytes count, liver enzymes, C3 and C4 levels at baseline and during TCZ treatment; episodes of infections, allergic reactions, and AID were captured and analyzed.
Results Thirty five pts out of 85 RA pts treated with TCZ, at our center, had serial measurements of serum complement concentration. Fourteen pts (mean age 58.3 years, mean disease duration 8.6 years) developed low C4 levels (9 had also low C3). Mean TCZ treatment period was 4.6 years (range 1-10 years). All patients had normal complement levels at baseline. Seven pts developed persistent leukopenia, 3 pts had persistent thrombocytopenia, 3 pts developed liver enzymes elevation. No serious bacterial infections or new onset AID occurred during follow up. One patient developed a severe allergic reaction. Persistent leukopenia was observed only in 2 out of 21 pts with normal complement levels, as opposed to 5 out of 14 pts with hypocomplementemia. No patients with normal complement levels developed thrombocytopenia. No significant differences regarding previous biologic or concomitant DMARD's treatment were found between the 2 groups of pts.
Conclusions Long-term follow up of RA pts treated with TCZ who developed hypocomplementemia did not reveal an increased rate of serious bacterial infections or AID. Persistent leukopenia and thrombocytopenia were frequent in these pts; the relationship to hypocomplementemia needs to be further elucidated.
Disclosure of Interest None declared