## Amyloid Protein Classification **Key Point:** AL amyloidosis (primary amyloidosis) results from misfolding and aggregation of immunoglobulin light chains (kappa or lambda), produced by clonal plasma cells or B lymphocytes. ### Source and Pathogenesis - **AL amyloid** originates from **monoclonal immunoglobulin light chains** (kappa ~60%, lambda ~40%) - Produced by plasma cell dyscrasia (often subclinical) - No underlying chronic inflammation required - Most common form of amyloidosis in developed countries ### Distinction from Other Amyloid Types | Amyloid Type | Precursor Protein | Clinical Context | Organs Affected | |---|---|---|---| | **AL** | Ig light chains (κ or λ) | Primary; plasma cell disorder | Heart, kidney, nerve, GI | | **AA** | Serum amyloid A | Secondary; chronic inflammation | Kidney, liver, spleen | | **Aβ2M** | β2-microglobulin | Dialysis-related | Joints, bone, carpal tunnel | | **ATTR** | Transthyretin | Hereditary or wild-type | Nerve, heart | **High-Yield:** AL amyloidosis is the most common systemic amyloidosis in the West; AA amyloidosis is more common in developing countries with chronic infections (TB, leprosy). **Clinical Pearl:** AL amyloidosis typically presents with restrictive cardiomyopathy, nephrotic syndrome, or peripheral neuropathy in patients aged 50–70 years.
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