Abstract 4146682: Rarer Than Rare: AL Amyloidosis Presenting as Abdominal Amyloidomas

Case: A 52-yr-old man with weight loss and urinary hesitancy for 4 months underwent a CT urogram. No urologic abnormalities were noted but there was an incidental finding of intraperitoneal nodules and a perigastric mass. Biopsy of the perigastric lymph nodes showed abundant amyloid deposits, consistent with amyloidoma. Systemic amyloidosis workup was started. Serum immunofixation showed an IgG lambda M spike of 0.1 g/dL, and serum free light chain ratio was 0.17 (k/l = 10/60, mg/L). The tumor board recommended biopsy of other abdominal sites to distinguish plasmacytoma from amyloidoma. Biopsy showed amyloidosis with benign reactive lymph nodes and small clusters of lambda restricted plasma cells suggesting amyloidoma/plasmacytoma. Bone marrow biopsy showed 15% plasma cells, confirming multiple myeloma/amyloidosis overlap. Daratumumab-cyclophosphamide-bortezomib-dexamethasone (DARA-CyBorD) induction therapy was initiated. Transthoracic echocardiogram (TTE) showed normal biventricular function and moderate concentric hypertrophy. A cardiac MRI (CMR) then confirmed features of early amyloidosis. Light chains normalized with therapy but repeat bone marrow biopsy showed 5% lambda restricted plasma cells. Given the biopsy results and cardiac amyloid, consolidative autologous stem cell transplant was pursued to achieve a deep hematological response. Discussion: AL amyloidosis is a rare but fatal disease. Cardiac involvement is seen in > 75% patients and degree of cardiac infiltration determines median survival. The initial presentation of intra-abdominal amyloidomas is highly unusual and only reported in case series in literature. A finding of amyloidoma should prompt workup for systemic amyloidosis. Cardiac workup should be undertaken even in the absence of overt symptoms. TTE findings in early cardiac amyloid are highly non-specific and can, therefore, be easily missed. A high index of suspicion is needed in this cohort with advanced imaging being pursued for any abnormality such as moderate concentric hypertrophy. Recognition of early cardiac involvement was key in deciding the chemotherapy regimen and in the decision to pursue autologous stem cell transplant for long term remission.