Apolipoprotein A-IV Cardiac Amyloidosis Diagnosed by Mass Spectrometry-Based Proteomic Analysis.

BACKGROUND

Apolipoprotein A-IV amyloidosis (AApoA-Ⅳ) is a rare subtype of cardiac amyloidosis (CA) and is often overlooked because of its clinical similarity to transthyretin (ATTR) CA.

CASE SUMMARY: An 82-year-old man presented with heart failure with preserved ejection fraction. His clinical features, including grade 1 uptake on 99mTc-pyrophosphate scintigraphy, closely mimicked ATTR CA. Histologic examination revealed intracellular Congo red-positive amyloid deposits and characteristic electron microscopic findings. Mass spectrometry-based proteomic analysis confirmed the diagnosis of AApoA-IV CA.

DISCUSSION: Although the pathologic significance of the unique histologic features remains unclear, they may represent distinguishing characteristics of AApoA-IV amyloidosis.

TAKE-HOME MESSAGES: AApoA-IV CA typically presents with elderly-onset heart failure with preserved ejection fraction and may show positive uptake on bone scintigraphy. Differentiation from ATTR CA is possible based on characteristic histopathologic findings and mass spectrometry-based proteomic analysis.