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Alpha-1-antitrypsin deficiency
1Department of Pediatrics, Washington University School of Medicine, Missouri 63110, USA.
Insights
Alpha 1-antitrypsin deficiency (PIZZ) is a common genetic disorder causing liver disease in children and adults, and pulmonary emphysema. Liver disease in PIZZ individuals may stem from toxic mutant alpha 1-antitrypsin Z accumulation in liver cells.
Area of Science:
- Genetics
- Hepatology
- Pulmonology
Background:
- Alpha 1-antitrypsin (AAT) deficiency (PIZZ) is the most frequent genetic cause of pediatric liver disease, affecting 1 in 1600-2000 births.
- It is also linked to adult chronic liver disease, hepatocellular carcinoma, and pulmonary emphysema.
- Liver disease pathogenesis involves toxic mutant AATZ accumulation in the endoplasmic reticulum, distinct from emphysema's proteolytic mechanism.
Purpose of the Study:
- To summarize the understanding of alpha 1-antitrypsin deficiency-associated liver disease.
- To highlight the genetic basis and clinical manifestations of PIZZ.
- To discuss current diagnostic and therapeutic approaches.
Main Methods:
- Review of existing literature on alpha 1-antitrypsin deficiency.
- Analysis of screening data regarding PIZZ prevalence and clinical outcomes.
- Discussion of diagnostic techniques like isoelectric focusing.
Main Results:
- Only 10-15% of PIZZ individuals develop clinically significant liver disease by age 20.
- A subset of PIZZ individuals may be predisposed due to inefficient endoplasmic reticulum degradation of mutant AATZ.
- Diagnosis relies on identifying altered AATZ migration patterns.
Conclusions:
- Alpha 1-antitrypsin deficiency is a significant genetic disorder with diverse clinical outcomes.
- Liver disease is attributed to intracellular accumulation of mutant AATZ.
- Management is primarily supportive, with liver or lung transplantation for severe cases.
Abstract:
Homozygous PIZZ alpha 1-antitrypsin deficiency, which has an incident of 1 in 1600 to 1 in 2000 live births, is the most common genetic cause of liver disease in children. It is also associated with chronic liver disease and hepatocellular carcinoma in adults. It is a well-known cause of pulmonary emphysema. Although emphysema is due to uninhibited proteolytic destruction of the connective tissue backbone of the lung, liver disease is thought to result from the toxic effects of the mutant alpha 1AT molecule retained within the endoplasmic reticulum of liver cells. Screening studies done by Sveger in Sweden have shown that only 10 to 15% of the PIZZ population develop clinically significant liver disease over the first 20 years of life. Recent studies have suggested that a subgroup of PIZZ individuals are predisposed to liver injury because of an inefficient degradation of mutant alpha 1ATZ within the endoplasmic reticulum. Altered migration of the abnormal alpha 1ATZ molecule in isoelectric focussing gels is the basis of the diagnosis of alpha 1AT deficiency. Treatment of alpha 1AT deficiency-associated liver disease is mostly supportive. Liver replacement therapy has been used successfully for severe liver injury. An increasing number of patients with severe emphysema have undergone lung transplantation.