Late-onset deep surgical-site infection after posterior lumbar interbody fusion in a patient treated with tocilizumab; unusual changes in inflammatory markers. 
To describe a case of late-onset deep surgical-site infection (SSI) after posterior lumbar interbody fusion in a patient treated with tocilizumab (TCZ) for rheumatoid arthritis (RA), with emphasis on the clinical symptoms and changes in inflammatory markers such as white blood cell (WBC) count and C-reactive protein (CRP) level.  A 74-year-old woman with 3-year history of RA underwent posterior lumbar interbody fusion at the L4/5/S1 level.  After confirmation of no clinical symptom of SSI postoperatively, we decided to use TCZ for the patient after 2 months postoperatively.  At 8 months after beginning of TCZ, she suffered from sudden onset of severe low back pain (LBP) with fever (38 °C) 1 day after administration of TCZ.  Local tissues around the operative wound showed no sign of redness, warmth, or swelling.  Increases in body temperature, WBC count, and CRP level were well suppressed by TCZ.  Magnetic resonance imaging performed 2 weeks after onset of LBP revealed deep SSI.  After surgical debridement and administration of the sensitive antibiotics, no clinical signs of recurrent spondylitis or osteolysis of vertebral body have been seen for 3 years.  As TCZ strongly suppresses inflammatory reactions, detecting deep SSI based on local and systemic findings and laboratory data is quite difficult.  Care must be taken regarding SSI when patients treated with TCZ complain of long-lasting LBP after lumbar surgery.