Alpha-1 antitrypsin deficiency: the liver
- Lesion
A misfolded protein gets stuck inside liver cells, harming the liver, while its absence in blood lets the lungs be digested.
What it is
Alpha-1 antitrypsin is a protease inhibitor made by hepatocytes that protects tissues, above all the lung, from neutrophil elastase. In the PiZZ genotype a single amino acid change makes the protein misfold and polymerize in the endoplasmic reticulum. Too little reaches the blood (emphysema), and the retained polymers injure hepatocytes (neonatal hepatitis, chronic hepatitis, cirrhosis, HCC). It is a co-dominant disorder.
Structure
- Round to oval cytoplasmic globules, pink on H&E, magenta with PAS after diastase, mostly in periportal hepatocytes.
- Neonates: giant-cell hepatitis with cholestasis; adults: chronic hepatitis or cirrhosis.
Step by step
- The Z allele changes one amino acid, so the protein folds slowly and wrongly.
- Misfolded molecules polymerize and are retained in the hepatocyte ER.
- The unfolded protein response, autophagy and ER stress injure the cell, which may die.
- Repeated injury and regeneration lead to fibrosis, cirrhosis and HCC.
- Serum alpha-1 antitrypsin is low; neutrophil elastase digests alveolar walls: emphysema.
Markers
- PAS with diastase
- A1AT immunostain
Test yourself
Think of the answer, then tap the question to see it.
What do PAS-positive, diastase-resistant globules in periportal hepatocytes indicate?
Retained misfolded alpha-1 antitrypsin, typical of the PiZZ genotype.
Why are the liver and lung injured by different mechanisms in A1AT deficiency?
The liver suffers from toxic accumulation of misfolded protein; the lung from lack of circulating inhibitor, which lets elastase destroy alveoli.
What kind of emphysema occurs in A1AT deficiency?
Panacinar emphysema, predominantly in the lower lobes, at a young age and worse with smoking.
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Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Alpha-1 antitrypsin deficiency: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Alpha-1 antitrypsin deficiency: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.