A 58-year-old man from Tamil Nadu presents with progressive dyspnea, orthopnea, and bilateral ankle edema for 6 months. On examination, he has a blood pressure of 145/92 mmHg, heart rate 92/min, and a restrictive pattern on spirometry. Echocardiography reveals a thickened ventricular wall with a 'granular sparkling' appearance and preserved ejection fraction. Serum creatinine is 1.8 mg/dL with proteinuria (2.5 g/24 h). A kidney biopsy shows deposits that stain positive with Congo red and exhibit apple-green birefringence under polarized light. What is the most likely type of amyloidosis in this patient?

Explanation

## Clinical Diagnosis: AL Amyloidosis ### Key Clinical Features **Key Point:** The constellation of restrictive cardiomyopathy, nephrotic-range proteinuria, and renal dysfunction in a middle-aged patient with no prior chronic inflammatory disease points to AL (light chain) amyloidosis. ### Pathological Hallmark **High-Yield:** Congo red staining with apple-green birefringence under polarized light is the gold standard for amyloid identification. This confirms amyloid deposition, but the *type* must be determined by immunohistochemistry or mass spectrometry. ### Distinguishing AL from Other Types | Feature | AL Amyloidosis | AA Amyloidosis | AH Amyloidosis | Aβ2M Amyloidosis | |---------|---|---|---|---| | **Precursor protein** | Misfolded light chains (κ or λ) | Serum amyloid A (acute phase reactant) | Apolipoprotein A-I variant | β2-microglobulin | | **Associated condition** | Plasma cell dyscrasias, multiple myeloma | Chronic inflammation (TB, RA, chronic osteomyelitis) | Familial hereditary amyloidosis | Chronic kidney disease on long-term dialysis | | **Cardiac involvement** | Common (restrictive CM, conduction defects) | Rare | Rare | Rare | | **Renal involvement** | Common (nephrotic syndrome) | Common | Rare | Rare | | **Age of onset** | Middle to older age | Any age with chronic disease | Early (hereditary) | Dialysis patients | | **Immunohistochemistry** | Positive for κ or λ light chains | Positive for AA | Positive for apoA-I | Positive for β2M | ### Clinical Pearl **Clinical Pearl:** AL amyloidosis is the most common systemic amyloidosis in developed countries and frequently presents with a triad of: 1. Restrictive cardiomyopathy (most frequent cardiac manifestation) 2. Nephrotic syndrome with progressive renal failure 3. Absence of prior chronic inflammatory disease The patient's age, presentation with cardiac and renal involvement simultaneously, and lack of history of chronic infection or inflammation make AL amyloidosis the diagnosis. ### Diagnostic Confirmation **Key Point:** Immunohistochemistry or mass spectrometry of the amyloid deposit is required to confirm AL type and identify the specific light chain (κ or λ). Serum and urine protein electrophoresis may reveal a monoclonal spike. ### Management Implications **High-Yield:** AL amyloidosis requires chemotherapy (bortezomib-based regimens) to suppress the plasma cell clone producing the misfolded light chains, unlike AA amyloidosis which requires treatment of the underlying inflammatory disease.