Natural Killer T Cell Intravascular Lymphoma With Presentation of Musculoskeletal Pain: A Case Report

Natural killer T cell intravascular lymphoma is a rare category of lymphoma among older individuals. The presentation of natural killer T cell lymphoma varies, causing diagnostic challenges for clinicians. Thus far, only a few studies have reported this condition in the context of musculoskeletal symptoms. We encountered a case of natural killer T cell intravascular lymphoma in a patient who presented with symptoms of sternoclavicular arthritis and femoral pain. The initial diagnosis was undifferentiated hematologic malignancy because undifferentiated hematologic malignant cells were seen on the bone marrow biopsy. Further examination showed that the patient had a high fever and abnormal cells in the blood. Flow cytometry findings revealed the abnormal cells as CD16 and CD56 positive, leading to the diagnosis of natural killer T cell intravascular lymphoma. This is the first report indicating the possibility of natural killer T cell intravascular lymphoma as one of the differential diagnoses of acute joint and muscular pains among older patients and the importance of assessing multiple organs, including musculoskeletal organs, to diagnose intravascular lymphoma.