Perugini Grade 3 Uptake Does Not Exclude AL Cardiac Amyloidosis: When Noninvasive Diagnosis Fails.

BACKGROUND: Bone scintigraphy has improved noninvasive diagnosis of cardiac amyloidosis, but interpretation remains challenging when monoclonal gammopathy is present. CASE SUMMARY: A 76-year-old man with heart failure with preserved ejection fraction, chronic kidney disease, permanent atrial fibrillation, and persistent troponin elevation underwent coronary angiography showing significant left anterior descending artery stenosis treated with percutaneous coronary intervention. Persistent symptoms, recurrent heart failure decompensations, disproportionate natriuretic peptide elevation, increased wall thickness, and apical sparing raised suspicion for infiltrative cardiomyopathy. Laboratory testing revealed monoclonal gammopathy. Tc-99m-pyrophosphate scintigraphy showed Perugini grade 3 uptake, strongly suggestive of transthyretin cardiac amyloidosis (ATTR-CA), but endomyocardial biopsy established light-chain (AL) cardiac amyloidosis. AL-directed therapy was initiated, but the patient died of severe pneumonia with respiratory failure. DISCUSSION: In the presence of monoclonal gammopathy, even Perugini grade 3 uptake does not establish ATTR-CA. Recent ischemic injury may further confound scintigraphic interpretation. TAKE-HOME MESSAGE: Tissue confirmation remains essential for accurate diagnosis and timely AL-directed therapy.