A 65-year-old man presents with restrictive cardiomyopathy. Endomyocardial biopsy shows amorphous eosinophilic extracellular deposits that stain positive with Congo red and show apple-green birefringence under polarized light. What is the most likely etiology?
- A Hemochromatosis
- B Cardiac amyloidosis (AL type) ✓
- C Sarcoidosis
- D Endomyocardial fibrosis
Correct answer: B. Cardiac amyloidosis (AL type)
Explanation
Congo red positivity with apple-green birefringence under polarized light is pathognomonic for amyloid. AL amyloidosis (primary amyloidosis) is the most common cause of restrictive cardiomyopathy in older adults, caused by deposition of immunoglobulin light chains. Hemochromatosis shows Prussian blue-positive iron deposits. Sarcoidosis shows non-caseating granulomas. Endomyocardial fibrosis shows dense fibrous tissue without amyloid staining. The apple-green birefringence is the key diagnostic feature.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.