A 35 year old male with no past medical history presents with increasing shortness of breath and dyspnea on exertion and lower extremity edema increasing over the past month. His temperature is 37.0, blood pressure 90/60, heart rate 100, respirations 20, and oxygen saturation 95% on room air. Physical examination reveals decreased breath sounds at the left base without wheezing, elevated jugular venous pressure markedly worse with inspiration, a regular rhythm with an S4 heart sound and 2+ lower extremity pitting edema. Laboratory studies are normal. Cardiac biopsy revealed green birefringence with Congo red staining. Genetic testing reveals a mutation in the transthyretin gene. Which of the following is the correct diagnosis?