A 48-year-old man presented with rapidly progressive heart failure and monoclonal gammopathy of uncertain significance. No specific cause was detected on endomyocardial biopsy. As the heart failure worsened, he also developed progressive skeletal myopathy. This provided the clue to the diagnosis, and cardiac function recovered rapidly with cause-directed therapy. (Level of Difficulty: Intermediate.).
Keywords: MGUS, monoclonal gammopathy of uncertain significance; SLONM, sporadic late-onset nemaline myopathy; cardiomyopathy; chronic heart failure; echocardiography; imaging; right-sided catheterization.
© 2020 The Authors.