Abstract Body (Do not enter title and authors here): Case: A 62-year old male with a history of chronic kidney disease and paroxysmal atrial fibrillation presented with several months of fatigue, a progressive decline in functional status (NYHA IIIb-IV), weight loss, and intermittent lower extremity swelling. Blood pressure was 92/72 mmHg on presentation, and heart rate was 90 bpm. Physical examination revealed a jugular venous pressure of 12-14 cm H2O and 2+ bilateral lower extremity edema with mild wheezing.

Methods/workup: Laboratories are shown in Table 1 and were notable for a serum free light chain ratio of 0.14. Transthoracic echocardiogram (figure 1) revealed a left ventricular (LV) ejection fraction of 33% with increased LV wall thickness and severe bi-atrial enlargement. Bone marrow biopsy revealed 2% lambda restricted plasma cells without evidence of amyloid deposits; metastatic bone survey was negative. A fat pad biopsy and endomyocardial biopsy stained negative for amyloid with Congo red. Cardiac MRI showed diffuse, circumferential subendocardial late gadolinium enhancement, most compatible with cardiac amyloidosis (figure 2). The patient also had a chest CT scan that demonstrated a few patchy nodular pulmonary infiltrates. Given his extensive negative workup, he was referred to pulmonary and endobronchial biopsy was positive for amyloid on Congo red staining (figure 3). Biopsy tissue typing revealed Lambda subtype AL amyloidosis.

Management: The patient was started on Daratumumab, Cyclophosphamide, Bortezomib, and Dexamethasone by Hematology. Unfortunately, about a month after his diagnosis, he developed worsening heart failure despite treatment. He was admitted to an outside hospital with refractory cardiogenic shock and passed away during that admission.

Discussion: The diagnosis of AL amyloidosis requires a high index of suspicion for prompt diagnosis and treatment. We present a case in which cardiac amyloidosis was suspected based on the patient’s clinical picture and cardiac imaging; however, multiple initial biopsies were negative. An expedited, multimodal and interdisciplinary diagnostic assessment is imperative as prognosis with chemotherapy is highly dependent on extent of AL disease, patient functional status, and presence of cardiac compromise. Elevated natriuretic peptides, troponins, autonomic dysfunction, and hypotension are negative prognostic features.