Table 4 Summary of side effects of tocilizumab from summary of product characteristics in relation to patients in our case series

Increased risk of infection—some studies have suggested a higher rate of serious infection with tocilizumab [24], specifically causing skin and subcutaneous infections [25], and complications of diverticulitis. The SmPC states to pause administration of tocilizumab until the infection is controlled

Case D and M both experienced cellulitis, that may have been independent or a side effect of tocilizumab. Both resolved with a pause in treatment of three and two doses, respectively

Liver function derangement—elevation in alanine aminotransferase (ALT) or aspartate aminotransferase (AST). If there is a change of greater than five times the upper limit of normal (ULN), the SmPC states to discontinue tocilizumab; if the change is between three and five times the ULN, to pausing dosing; and if the change is between one and five times the ULN, to dose modify

Liver function derangement was noted for both case H and J—case J stopped the treatment completely due to other causes, whilst case H paused treatment for 1 month, after which it resolved

Transient neutropenia—the SmPC states to not initiate tocilizumab if the neutrophil count is below 2 × 10⁹/L, to pause dosing if between 0.5 and 1 × 10⁹/L, and to stop if less than 0.5 × 10⁹/L

Case G skipped one dose due to a neutropenia

Thrombocytopenia—SmPC guidance states to discontinue tocilizumab if platelets are less than 50, and to pause dosing if between 50 and 100

Bruising was experienced by case B, with a 1 month pause in treatment

Elevation in lipid profile—including cholesterol, lipoproteins, and triglycerides. The SmPC suggests testing for these 1–2 months after initiation of tocilizumab, and starting appropriate hyperlipidemia management if required

Hypersensitivity and infusion reactions—hypersensitivity is rare with subcutaneous tocilizumab [13], whereas infusion reactions are more common [25]