False flag: myocardial microcalcification mimicking Perugini grade 3

A 31-year-old man with end-stage renal disease and prior parathyroidectomy for severe tertiary hyperparathyroidism presented with marked symmetric left-ventricular hypertrophy and repolarization abnormalities on electrocardiography (Panel A). Initial right-ventricular biopsy, coronary angiography, and comprehensive genetic testing for cardiomyopathies—including Anderson–Fabry disease—were unremarkable. Cardiac magnetic resonance imaging (CMR) demonstrated concentric hypertrophy (20 mm) (Supplementary data online, Video), markedly reduced native T1 values (497 ms), diffuse intense late gadolinium enhancement (Panel B), and an extracellular volume >50%, suggesting an infiltrative or storage disease. Non-contrast computed tomography showed mitral annular calcification with normal native myocardial Hounsfield units (40–50 HU; Panel C). 99mTc-DPD scintigraphy demonstrated strong myocardial tracer uptake consistent with Perugini grade 3 (Panel D), suggestive of transthyretin cardiac amyloidosis. Because the scintigraphic pattern conflicted with the atypically low native T1 values, a left-ventricular biopsy was performed. Histology revealed pronounced interstitial fibrosis with fine granular myocardial microcalcifications (200×: purple deposits in the fibrotic area) and no amyloid (Panel E), confirming diffuse myocardial microcalcification secondary to severe tertiary hyperparathyroidism in chronic kidney disease.1 These calcium depositions explained both the markedly low native T1 values due to rapid dephasing and the Perugini grade 3 appearance.