In hereditary hemochromatosis, iron deposition in hepatocytes leads to cirrhosis through which primary mechanism?

Explanation

## Iron-Induced Hepatic Injury in Hemochromatosis **Key Point:** Iron causes hepatocyte injury and fibrosis primarily through **oxidative stress**. Excess iron participates in the Fenton reaction, generating hydroxyl radicals and other reactive oxygen species (ROS) that damage cellular lipids, proteins, and DNA. ### Mechanism of Iron-Catalyzed Injury **High-Yield:** The Fenton reaction is the central mechanism: $$Fe^{2+} + H_2O_2 \rightarrow Fe^{3+} + OH^\bullet + OH^-$$ The hydroxyl radical (OH•) is highly reactive and causes: 1. **Lipid peroxidation** — damage to cell membranes and organelles 2. **Protein oxidation** — inactivation of enzymes and structural proteins 3. **DNA damage** — mutations and apoptosis 4. **Mitochondrial dysfunction** — energy depletion ### Progression to Cirrhosis ```mermaid flowchart TD A[Excess iron in hepatocytes]:::outcome --> B[Fenton reaction generates ROS]:::action B --> C[Lipid peroxidation & protein damage]:::action C --> D[Hepatocyte apoptosis & necrosis]:::outcome D --> E[Activation of hepatic stellate cells]:::action E --> F[Collagen deposition & fibrosis]:::action F --> G[Cirrhosis]:::urgent B --> H[Iron-induced inflammation]:::action H --> E ``` **Clinical Pearl:** Iron also induces hepatic stellate cell activation, amplifying the fibrotic response. This explains why iron chelation therapy, if started early, can halt or even reverse early fibrosis. ### Iron Deposition Pattern in Hemochromatosis | Tissue | Iron Deposition | Consequence | |--------|-----------------|-------------| | Hepatocytes | Cytoplasmic (ferritin & hemosiderin) | Cirrhosis, hepatocellular carcinoma | | Pancreatic β-cells | Cytoplasmic | Diabetes mellitus ("bronze diabetes") | | Cardiac myocytes | Cytoplasmic | Dilated cardiomyopathy, arrhythmias | | Pituitary gonadotrophs | Cytoplasmic | Hypogonadism | | Joints (synovium) | Synovial lining | Arthropathy (pseudo-gout) | **Mnemonic:** **ROS = Reactive Oxygen Species** — the key driver of iron-induced tissue damage in hemochromatosis.