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

RATIONALE: 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. PATIENT CONCERNS: We present a 50-year-old patient with previous B cell lymphoma and subsequent multiple myeloma (MM). DIAGNOSIS: A diagnosis of B cell lymphoma and MM was made. INTERVENTIONS: The patient was treated with a combination of haploidentical CD19-chimeric antigen receptor (CAR) T cells and BCMA-CAR T cells. OUTCOMES: After CAR T cell therapy, the monoclonal plasma cells in the bone marrow and M protein disappeared. LESSONS: 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.