Severe pulmonary toxicity related to carfilzomib use: a rare but serious side effect.

Carfilzomib is a selective proteosome inhibitor that is commonly used in the treatment of relapsed or refractory multiple myeloma. Carfilzomib has been commonly associated with respiratory side effects. It can rarely also cause fatal pulmonary toxicity. We present a case of a man in his 50s with plasma cell leukaemia who was initiated on treatment with carfilzomib and dexamethasone. He developed severe pneumonitis requiring oxygen via a high-flow nasal cannula. After an extensive workup, a temporal relationship between the carfilzomib use and exacerbation of the pulmonary symptoms was found. Carfilzomib was permanently discontinued, and the patient was started promptly on methyl prednisolone with complete resolution of his symptoms. Due to the associated risk of mortality if not detected early, we wish to highlight this rare but serious pulmonary toxicity associated with carfilzomib that was managed with high-dose glucocorticoids.