Symptomatic elevation creatine kinase following treatment of rheumatoid arthritis with baricitinib

The aim of RA treatment is to achieve reduction of disease activity and prevent joint damage and disability. Baricitinib is a synthetic small molecule which targets the JAK/STAT pathway which is implicated in the inflammatory response in RA. Baricitinib selectively targets JAK1 and JAK2 and has been shown to have efficacy in treating patients with RA. Common adverse effects reported during baricitinib therapy includes infection, asymptomatic changes in laboratory parameters including changes in neutrophil, lymphocyte, platelet counts, alanine aminotransferase, cholesterol, creatinine and creatine kinase (CK). We report the first two documented cases in Australia of baricitinib-induced symptomatic elevation of CK.