In the pathogenesis of atherosclerosis, which of the following is the earliest morphologic change visible in the arterial wall?

Explanation

## Morphologic Progression of Atherosclerosis **Key Point:** The fatty streak is the earliest morphologically identifiable lesion in atherosclerosis, though endothelial dysfunction precedes it functionally. ### Stages of Atherosclerotic Lesion Development ```mermaid flowchart TD A[Endothelial Dysfunction<br/>Increased LDL permeability]:::outcome --> B[Lipid Accumulation<br/>in Intima]:::outcome B --> C[Fatty Streak<br/>Foam cells + lipid]:::outcome C --> D[Intermediate Lesion<br/>Smooth muscle migration]:::outcome D --> E[Fibrous Plaque<br/>Thick fibrous cap]:::outcome E --> F[Complicated Lesion<br/>Necrotic core, calcification]:::outcome ``` ### Characteristics of the Fatty Streak 1. **Composition:** - Macrophage-derived foam cells (lipid-laden macrophages) - Oxidized LDL (oxLDL) in intimal space - T lymphocytes - Minimal smooth muscle involvement 2. **Timing:** - Appears in childhood in susceptible individuals - Visible on gross examination as yellow streaks along coronary arteries - Reversible in early stages 3. **Microscopic appearance:** - Foamy macrophages with lipid droplets - Intimal thickening - No significant fibrous cap **High-Yield:** Fatty streaks are **reversible lesions** if risk factors are modified early; fibrous plaques are largely irreversible. This distinction is clinically important for primary prevention. **Clinical Pearl:** Fatty streaks can be found in the aortas of children as young as 5–10 years old in developed countries, reflecting early atherosclerotic disease. **Mnemonic:** **"FOAM = First Obvious Atherosclerotic Morphology"** — the fatty streak is the first morphologically visible stage.