Case report: simultaneous occurrence of multiple myeloma and non-Hodgkin lymphoma treated by CAR T therapy

B cell lymphoma can co-occur with multiple myeloma (MM), and the prognosis in this case is usually poor. We propose the combination of CD19-chimeric antigen receptor (CAR) T cells and BCMA-CAR T cells for the treatment of such patients to obtain a superior prognosis. We present a 50-year-old patient with previous B cell lymphoma and subsequent multiple myeloma (MM). A diagnosis of B cell lymphoma and MM was made. The patient was treated with a combination of haploidentical CD19-chimeric antigen receptor (CAR) T cells and BCMA-CAR T cells. After CAR T cell therapy, the monoclonal plasma cells in the bone marrow and M protein disappeared. The combination therapy of CD19- and BCMA-CAR T cells is an effective measure to treat patients with concomitant or borderline cases of B cell lymphoma and MM.