Atypical clinical presentation of inflammatory marker negative septic arthritis, osteomyelitis, and bacteremia following a single dose of tocilizumab in the treatment of COVID-19: a case report

Background: Tocilizumab is an immunomodulating agent that inhibits the inflammatory cascade via interleukin-6 (IL-6) signaling. A recent meta-Analysis written by the World Health Organization, and other large, randomized trials, have found that the medication results in reduced all-cause mortality in the treatment of severe coronavirus disease 2019 (COVID-19) illness, likely by targeting aberrant inflammatory pathways. With the medication now recommended by infectious diseases societies in the treatment of COVID-19, many providers will begin using this medication in critically ill patients, and for some it will be their first exposure to the medication and its side effects. Although atypical secondary infections have been observed following multiple administrations of tocilizumab, our case is significant as it displays an atypical presentation of invasive bacterial illness and sepsis following a single dose. Case Description: Our case consists of a 52-year-old man with severe COVID-19 pneumonitis who was given tocilizumab due to worsening respiratory status and elevating inflammatory markers, who later developed severe, invasive bacterial disease with minimal objective findings suggesting severe illness. Six days following tocilizumab administration, the patient was diagnosed with Staphylococcus aureus (S. aureus) bacteremia, septic arthritis, and osteomyelitis, at which time inflammatory markers were within normal limits, he was no longer febrile or tachycardic, and his only objective findings suggesting illness were a tender shoulder with an isolated, neutrophilic predominant leukocytosis. This complication resulted in a washout of a septic joint, a 6-week course of intravenous antibiotics, and a 59-day hospitalization. The patient was discharged without new chronic medical issues, including a lack of new end-organ dysfunction or chronic pain of the joint affected by septic arthritis. Conclusions: This case demonstrates an atypical presentation of gram-positive systemic infection, displaying the complications which may develop with the use of immunomodulators. Because of the potential for severe infection with atypical, insidious presentation, a high index of suspicion should be maintained in all patients receiving these agents. © Journal of Emergency and Critical Care Medicine.