**Author Information** An event is serious (based on the ICH definition) when the patient outcome is:\* death\* life-threatening\* hospitalisation\* disability\* congenital anomaly\* other medically important event

A 52-year-old man developed drug-induced liver injury during treatment with tocilizumab for cytokine release syndrome.

The man was returned from Serbia to Montenegro on 10 March 2020. After 2 weeks, he developed dry cough and fever. He was tested positive for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Then, he was hospitalised and was diagnosed with coronavirus disease (COVID)-19 bilateral pneumonia. Subsequently, he started receiving off-label treatment with chloroquine, lopinavir/ritonavir, ceftriaxone and azithromycin as per state administration of Traditional Chinese Medicine protocol for COVID-19 and National Health Commission. Twelve days after hospitalisation, his chest multi-slice computed tomography (MSCT) showed bilateral basal pulmonary consolidation and ground-glass opacities. He needed mechanical ventilation. Hence, he was transferred to the ICU. He was sedated and mechanically ventilated with stable vital parameters for the first 4 days of ICU admission. Before the ICU admission, treatment with chloroquine was stopped, while he had received lopinavir/ritonavir for 3 days in the ICU. During the ICU admission, he also started receiving methylprednisolone. Treatment with azithromycin and ceftriaxone was continued. Six days after the ICU admission, his condition worsened, and chest radiography revealed the evidence of disease progression. His laboratory tests showed increased CRP, interleukin-6 (IL-6), fibrinogen and D-dimer levels, while lymphocyte count decreased. His AST level was normal, while the ALT level was slightly elevated. All microbiological analyses were negative. Based on radiological, clinical and laboratory analysis, a diagnosis of cytokine release syndrome was made. Subsequently, he started receiving IV tocilizumab 400mg (8 mg/kg) as per Lombardian and Chinese protocols. He had received 2 doses of tocilizumab with a 12h break between doses. His treatment with azithromycin, ceftriaxone and methylprednisolone were continued. One day after the administration of two tocilizumab doses, he had an acute liver injury. His abdominal ultrasound, serum levels of alkaline phosphatase, bilirubin and γ-glutamyl transferase were normal. As per Roussel Uclaf Causality Assessment Method/Council for International Organizations of Medical Sciences (CIOMS/RUCAM) method and European Association for the Study of the Liver guidelines, the causal relationship between drug-induced liver injury and tocilizumab was assessed as probably related. In view of his poor general condition, liver biopsy was not performed.

Several days after tocilizumab administration, the man\'s clinical condition improved with a remarkable decrease in CRP, IL-6 and D-dimer levels. Afterwards, his condition became complicated due to subcutaneous emphysema and bilateral pneumothorax \[*aetiologies not stated*\]. Therefore, a drain thoracostomy was performed. Ten days after receiving tocilizumab doses, his transaminase, IL-6, D-dimer and CPR levels almost became normal. Despite the resolution of cytokine release syndrome and recovery of laboratory test results, his condition still critical because of pulmonary issues.
