Azacitidine as a rare cause of reactive arthritis in a patient with acute myeloid leukemia

Azacitidine (AZA), a demethylating agent, is one of the mainstay treatments for patients with myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML) who are ineligible for curative allogeneic stem-cell transplantation and is recommended as first-line treatment in multiple countries. While arthralgia and myalgia have been commonly reported as side effects, the incidence of drug-induced reactive arthritis has only been reported twice so far.We present a retrospective overview of a clinical case of a 71-year-old patient that developed new cytopenias on a background of Chronic Lymphocytic Leukaemia and was diagnosed with therapy-associated AML. His treatment included an indefinite course of AZA to induce remission and optimise long-term survival which resulted in a satisfactory haematological response. However, after his ninth AZA cycle, he presented to the emergency department with knee swelling and erythema and conjunctivitis.Arthrocentesis of the knee revealed reactive arthritis with no crystal or organism growth. His symptoms were managed effectively with conservative management including NSAIDs, analgesia and temporary immobilization for joint rest. The adverse drug reaction probability score in our study was calculated as six and adverse drug reaction was thus assigned to the "probable" category.We report a case that points to AZA as a probable cause of arthritis flares in MDS patients. The current limitation of this study is the lack of available data, future reviews and research will aid in providing stronger evidence of a correlation between arthritis and AZA treatment.