A 58-year-old man from Mumbai presents with progressive dyspnea on exertion and orthopnea for 6 months. On examination, he has a blood pressure of 95/60 mmHg, elevated JVP, and bilateral ankle edema. Echocardiography shows a thick-walled left ventricle with restrictive filling pattern and ejection fraction of 45%. Cardiac biomarkers (troponin I, BNP) are markedly elevated. A endomyocardial biopsy shows Congo red-positive material with apple-green birefringence under polarized light. What is the most likely type of amyloid deposited in this patient's myocardium?

Explanation

## Clinical Presentation & Diagnosis This patient presents with **restrictive cardiomyopathy** — the hallmark cardiac manifestation of amyloidosis. The Congo red staining with apple-green birefringence under polarized light is pathognomonic for amyloid. ## Amyloid Type Identification **Key Point:** The clinical context and organ involvement are critical for identifying amyloid type. Cardiac amyloidosis in a middle-aged patient without chronic kidney disease, chronic inflammation, or dialysis history points to **AL (light chain) amyloidosis**. ### AL Amyloid (Light Chain) - Most common cause of cardiac amyloidosis in developed countries - Composed of misfolded immunoglobulin light chains (κ or λ) - Associated with plasma cell dyscrasias (often occult) - Presents with restrictive cardiomyopathy, conduction abnormalities, arrhythmias - Elevated cardiac biomarkers (troponin, BNP) are characteristic - Prognosis: poor without treatment (median survival ~4–6 years if untreated) ### Why Other Types Are Less Likely | Amyloid Type | Primary Organ(s) | Clinical Context | Why Not This Case | | --- | --- | --- | --- | | **AA (serum amyloid A)** | Kidney, liver, spleen | Chronic inflammation (TB, rheumatoid arthritis, chronic infections) | No history of chronic inflammatory disease; kidney not mentioned | | **AβM (β2-microglobulin)** | Bone, joints, carpal tunnel | Long-term dialysis (>5–10 years) | No mention of renal failure or dialysis | | **ATTRwt (wild-type transthyretin)** | Heart, carpal tunnel | Elderly men (>60 years), often asymptomatic | Age-appropriate, but ATTRwt typically presents at >70 years; this patient is 58 | **Clinical Pearl:** AL amyloidosis must be suspected in any patient with unexplained restrictive cardiomyopathy, especially with elevated troponin and BNP. Serum and urine protein electrophoresis, immunofixation, and free light chain assay are essential confirmatory tests. **High-Yield:** The combination of **restrictive cardiomyopathy + elevated cardiac biomarkers + Congo red positivity** in a middle-aged patient = **AL amyloidosis** until proven otherwise.