We describe the case of a 70-year-old Japanese woman with multiple myeloma with coagulopathy that was suspected of being due to paraprotein with lupus anticoagulants activity. A close examination of the cause of the prolonged aPTT revealed a positive for all endogenous inhibitors and the presence of LAs were suspected, including the results of the mixing test. Partial response was achieved with multiple chemotherapy regimens, but the coagulation abnormalities did not improve. However, EPd therapy reached a deeper response (normalized the FLC ratio and the achievement of deep minimal residual disease level) , and simultaneously, aPTT normalized and inhibitor disappeared. This suggests that a small amount of paraprotein has LA activity. The patient was successfully treated with rivaroxaban for thromboprophylaxis, without thrombotic or bleeding events. Therefore, in patients with multiple myeloma who have a prolonged aPTT, it is important to suspect the presence of LAs, perform a mixing test, and take appropriate prevention against thrombosis, which may lead to improved outcomes.

A 55-year-old woman was diagnosed with smoldering multiple myeloma (MM) in September 2021 and developed acute heart failure two months later. The patient was transferred to another hospital, where mitral valve replacement was performed for severe mitral regurgitation. Four months later, the patient developed acute renal failure and underwent continuous hemodiafiltration. She returned to our hospital for treatment of systemic amyloid light-chain (AL) amyloidosis, which later deteriorated to symptomatic MM. In April 2022, the patient underwent chemotherapy with subcutaneous daratumumab, cyclophosphamide, bortezomib, and dexamethasone (Dara sc-CyBorD). She achieved a very good partial response and the dobutamine treatment was discontinued at the end of the fifth course. The patient recovered from the severe heart failure. The patient was discharged and continued to receive outpatient chemotherapy. Our successful treatment of AL amyloidosis with severe heart failure using Dara sc-CyBorD is promising for patients ineligible for autologous hematopoietic stem cell transplantation, as a consolidation therapy due to organ damage.