Low white blood cells and tocilizumab: is there an increased infection risk in juvenile arthritis?

This study investigated if neutropenia (NP; a low number of white blood cells that fight off infections) increases the risk of infection in patients with juvenile idiopathic arthritis (JIA) taking tocilizumab (Actemra). They found that NP during tocilizumab treatment did not increase the risk of infections in these patients. 

Arthritis conditions are caused by excess inflammation. Systemic juvenile idiopathic arthritis (sJIA) and polyarticular course JIA (pcJIA) affect children under 18. JIA and pcJIA are treated with medication to reduce inflammation. Different drugs target different inflammatory proteins and chemicals. One important target is interleukin 6 (Il-6). Tocilizumab (TCZ) is a drug that attaches to the Il-6 receptor. This stops Il-6 from signaling to immune cells. Inflammation is then reduced. 

There are side effects associated with TCZ treatment. One of these is neutropenia (NP). NP is a reduction in neutrophils. Neutrophils are the most abundant white blood cell (WBC). WBCs have an important role in the immune system. Some evidence suggests that NP in TCZ-treated patients may increase the risk of infection. It is unclear if there is an increased risk of infections in patients with sJIA and pcJIA taking TCZ.

This study analyzed two clinical trials on TCZ in sJIA and pcJIA. 112 patients with sJIA and 188 patients with pcJIA were included. Patients were also taking other arthritis medications. NP was classified as normal and grade 1- 4. Grade 4 was the most severe NP level. The risk of infections was compared between patients taking TCZ and placebo. 

44.6% of patients with sJIA had normal or grade 1 NP. 70.7% of patients with pcJIA had normal or grade 1 NP. Grade 4 NP was not observed in pcJIA patients and was seen in 1.8% of those with sJIA.

In sJIA, the risk of infections was similar across NP grades. No serious infections were reported for grades 3/4 NP. 2 serious infections were reported for grades 1/2 NP. In pcJIA, the risk of infections was similar across NP grades. No serious infections were reported at any NP grade. 

The authors concluded that TCZ-induced neutropenia did not increase the risk of infections in patients with JIA.

Patients in this study were also taking other medication. This may have had an effect on the results. This study was funded by F. Hoffmann La Roche Ltd., the manufacturer of tocilizumab.

If you have any concerns regarding JIA treatment, please discuss this with your physician.