Risk factors for hypersensitivity reactions to tocilizumab introduction in systemic juvenile idiopathic arthritis

The objective of this study is to identify risk factors for hypersensitivity reaction (HSR) to tocilizumab (TCZ) in systemic juvenile idiopathic arthritis (sJIA).

Clinical records of 40 patients with sJIA administered TCZ at one center were retrospectively reviewed. Patients were divided into HSR or non-HSR groups depending on the presence of HSR between the first and third TCZ administrations; clinical and laboratory assessments, including serum cytokine profile, were compared.

Five patients displayed HSR following the third TCZ administration. They were significantly younger, shorter, and lighter, with a higher peak body temperature than non-HSR patients following the third administration. Their serum C-reactive protein (CRP) level was undetectable following the first administration but detectable by the third administration. Before the third administration, the white blood cell counts and serum levels of CRP and sTNFRII were significantly higher in the HSR group than in the non-HSR group. The serum levels of interleukin-18 and -6 before the third TCZ administration were higher and lower than those before the first administration in the HSR and non-HSR groups, respectively.

Patients with sJIA having a younger age, shorter stature, and lighter weight and those showing increased disease activity in the early period of TCZ administration may be at higher risk of TCZ-induced HSR.