Obstructive Intramural Coronary Amyloidosis: Uncommon or Under-Recognized Cause of Microvascular Angina?

BACKGROUND: Obstructive intramural coronary amyloidosis (OICA) can be the unique manifestation of cardiac amyloidosis (CA). The clinical onset may mimic ischemic heart disease as microvascular angina or myocardial infarction. CASE SUMMARY: We report an 83-year-old man with long-standing angina, recurrent ischemic symptoms, and persistently elevated troponin levels despite normal coronary angiographies, negative bone scintigraphy, and nondiagnostic cardiac magnetic resonance. Given the clinical suspicion for CA, endomyocardial biopsy was performed and showed extensive transthyretin amyloid deposition almost exclusively within the intramural coronary arterioles. These findings established the diagnosis of transthyretin wild-type CA with predominant OICA. DISCUSSION: Ischemic presentations of CA are increasingly recognized, but isolated OICA remains underdiagnosed. Our case demonstrates that minimal interstitial deposition with marked microvascular involvement may result in negative scintigraphy, confirming the key diagnostic role of endomyocardial biopsy when clinical suspicion remains high. TAKE-HOME MESSAGE: OICA can evade detection and should be suspected in patients with angina, troponin elevation, and normal coronary arteries.