A 54-year-old man presented at our facility with a 3-month history of exertional breathlessness and purple blotches around his eyes. Examination revealed bilateral periorbital and perioral ecchymosis, purpuric spots along his waist, and waxy papules on his eyelids. In addition, the patient had macroglossia with nodular infiltration and irregular indentations at the lateral margin of his tongue. The patient also had a raised jugular venous pressure and prominent atrial and ventricular waves. Further examination revealed a fourth heart sound over the left ventricular apex, as well as bilateral basal rales. All other systems were normal except for mild hepatomegaly. Routine hematologic and biochemical lab work was unremarkable. X-rays of the spine and skull were normal, but a chest x-ray showed mild cardiomegaly. An electrocardiogram showed a QS complex from leads V1 to V4 (a pseudo-infarction pattern). An echocardiogram showed biatrial enlargement, left ventricular hypertrophy with a left ventricular ejection fraction of 48%, a speckled pattern on the myocardium, a thickened interatrial septum, and mild pericardial effusion. A color Doppler revealed mild mitral and tricuspid regurgitation with a restrictive pattern of mitral valve flow. Serum protein electrophoresis was normal. WHAT IS YOUR DIAGNOSIS? HOW WOULD YOU TREAT THIS PATIENT?