Abstract
Multiple myeloma (MM) is a plasma B-cell malignancy characterized by immune dysfunction, with infection representing a major complication. Bacteria, including Streptococcus pneumoniae, are common pathogens in patients with MM, but reports on infections with nontuberculous mycobacteria (NTM) have been limited. We herein report a case of disseminated NTM infection in a patient with MM undergoing treatment with immunomodulatory drugs. At the diagnosis, the patient showed lymphocytopenia and was treated with clarithromycin, rifampicin, and ethambutol; however, culture positivity persisted, and the patient died. The possibility of NTM infection should be considered in cases of unexplained deterioration of the MM patient's general condition.