Interdisciplinary Approach to Diagnostic Challenges: A Case Study of Cardiac Amyloid Light-Chain (AL) Amyloidosis, Multiple Myeloma, and Ductal Carcinoma In Situ.

Amyloid light-chain (AL) amyloidosis is a disorder caused by abnormal plasma cells, and it may develop either as a primary disease or as a secondary condition associated with multiple myeloma. Due to the absence of specific clinical symptoms, its diagnosis is often challenging. Here, we present a case of cardiac amyloidosis secondary to multiple myeloma, incidentally complicated by ductal carcinoma in situ (DCIS). Although the breast cancer was diagnosed as stage 0 (DCIS), the patient's heart failure symptoms worsened following surgical resection. As a result, further evaluation by the cardiology department was performed, leading to a diagnosis of cardiac amyloidosis. Subsequently, a hematology consultation was obtained, and bone marrow biopsy revealed that clonal plasma cells accounted for more than 60% of bone marrow cellularity, confirming a diagnosis of multiple myeloma. The patient received daratumumab + bortezomib + cyclophosphamide + dexamethasone therapy, achieved a partial response, and has been alive for >2 years. This case is a valuable example of a patient who experienced a gradual onset of the symptoms of amyloidosis, including palpitations, pleural effusion, right and left heart failure, before a diagnosis could be made. It took a total of eight departments to make a diagnosis, as it was challenging. Even if no abnormalities are observed in a single examination, it is important to listen carefully to patient complaints, repeat the examination if necessary, and work with multiple departments to provide treatment.