Alpha 1-antitrypsin deficiency
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Synonyms and keywords:: Alpha-1-deficiency; Anti-protease deficiency;
For patient information, click here Template:DiseaseDisorder infobox
Overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
Alpha 1-antitrypsin deficiency (A1AD or Alpha-1) is a genetically inherited disorder that results in defective production of alpha 1-antitrypsin. Alpha 1-antitrypsin deficiency (A1AD) was discovered in 1963 by Carl-Bertil Laurell and Eriksson at the University of Lund, Sweden. In 1969, Sharp et al was the first to discover the association between liver disease and development of A1AD. There is no established system for the classification of alpha 1-antitrypsin deficiency. Alpha 1-antitrypsin (A1AT) is synthesized and secreted mainly by hepatocytes. Alpha 1-antitrypsin (A1AT) protects the lungs from proteases like the neutrophil elastase enzyme. Genetic mutation in the SERPINA1 gene results in decreased levels of alveolar alpha1 antitrypsin. Proteases accumulate in the alveoli causing a destruction of alveolar walls and resultant emphysema. Accumulation of alpha1-antitrypsin in hepatocytes results in chronic liver disease. Panacinar emphysema is commonly associated with AATD with loss of all portions of the acinus from the respiratory bronchiole to the alveoli. In alpha1-antitrypsin deficiency (AATD), the emphysematous areas are uniformly distributed throughout the lobule found more commonly in the basilar portions of the lung. Alpha 1-antitrypsin deficiency has to be differentiated from other conditions with similar presentation like autoimmune hepatitis, bronchiectasis, bronchitis, chronic obstructive pulmonary disease (COPD), cystic fibrosis, emphysema, primary ciliary dyskinesia (Kartagener Syndrome), viral hepatitis. Alpha 1-antitrypsin deficiency (A1AD) is more common in people of Northern European, Iberian, and Saudi Arabian descent. First degree relatives of patients with known AAT deficiency are at an increased risk for the condition. Smoking is risk factor for development of serious lung disease in patients with AAT deficiency. Risk for lung disease also increases with exposure to dust, fumes, or other toxic substances. According to the Spanish Society of Pneumology and Thoracic Surgery (SEPAR), all COPD patients should be screened for AATD at least once in their lifetime. All patients with unexplained liver disease with or without respiratory symptoms should be evaluated for alpha1-antitrypsin deficiency AATD. If left untreated, not all patients with deficient gene develop symptomatic emphysema or cirrhosis. The symptoms of alpha1-antitrypsin deficiency (AATD) in the first two decades of life are mainly of associated liver disease progressing to pulmonary manifestations appear later in life. Emphysema is seen in nonsmokers in the fifth decade of life and during the fourth decade of life in smokers. Less common associations are panniculitis and cytoplasmic antineutrophil antibody‒positive vasculitis. The most common cause of death is emphysema. Chronic liver disease is the second most common cause of death. Common complications of AATD include pneumothorax, pneumonia, acute exacerbation of airflow obstruction, and respiratory failure. Physical examination of patients with AATD is usually remarkable for signs characteristic of increased respiratory work, airflow obstruction and hyperinflation that varies according to the severity of emphysema. A reduced concentration of serum alpha1-antitrypsin levels is diagnostic of AATD. Laboratory findings consistent with the diagnosis of AATD include moderate-to-severe airflow obstruction with an FEV1 in the range of 30-40% of the predicted value, reduced vital capacity, increased lung volumes secondary to air trapping (residual volume >120% of predicted value) are usually present, and diffusing capacity values are reduced substantially (<50% of predicted value) in most symptomatic patients. On chest X-ray alpha1-antitrypsin deficiency (AATD) emphysema presents as a hyperlucent appearance because healthy tissue has been destroyed. On High-resolution CT (HRCT) scan of the chest, hypoattenuated areas resulting from a lack of lung tissue are panlobular and characteristic lower zone predominance. Patients with low or borderline serum levels are tested with phenotyping (serum levels < 100 mg/dL) by isoelectric focusing (IEF) is the most commonly used method to definitively detect the alpha1-antitrypsin phenotype that indicates a risk for AATD. Genotyping uses DNA extracted from circulating mononuclear blood cells that utilizes DNA amplification techniques with melt-curve analysis. Recommendations based on treatment guidelines for AATD include: Alpha 1-antitrypsin enzyme repletion, smoking cessation, long-acting inhaled bronchodilators, preventive vaccinations against influenza and pneumococcus, pulmonary rehabilitation for patients with functional impairment, supplemental oxygen if needed, lung transplantation, treatment of COPD exacerbation in all patients of AATD should include AAT repletion. Lung transplantation may be recommended for some patients with end-stage lung disease. Effective measures for the primary prevention of alpha 1-antitrypsin deficiency includes vaccination against hepatitis A and hepatitis B to decrease the risk of liver complications. Secondary prevention strategies following alpha1-antitrypsin deficiency (AATD) includes avoid cigarette smoking. Smoking accelerates the progression of emphysema in severely deficient individuals by as much as 15 years when compared to their nonsmoking controls. The ATS/ERS AAT Deficiency Task Force recommends that all exacerbations with purulent sputum be treated with early antibiotic therapy. Prompt and effective treatment of infections provides protection from additional lung injury from an influx of neutrophils into the alveolus.
Historical Perspective
Alpha 1-antitrypsin deficiency (A1AD) was discovered in 1963 by Carl-Bertil Laurell (1919–2001) and Eriksson at the University of Lund, Sweden. In 1969, Sharp et al were the first to discover the association between liver disease and development of A1AD.
Classification
There is no established system for the classification of alpha 1-antitrypsin deficiency.
Pathophysiology
Alpha 1-antitrypsin (A1AT) is synthesized and secreted mainly by hepatocytes. However, other sources of the enzyme include macrophages and bronchial epithelial cells.Alpha1-antitrypsin enzyme is a member of the serine protease inhibitor (serpin) family of proteins. Alpha 1-antitrypsin (A1AT) protects the lungs from proteases like the neutrophil elastase enzyme.Genetic mutation in the SERPINA1 gene results in decreased levels of alveolar alpha1 antitrypsin. Proteases accumulate in the alveoli causing a destruction of alveolar walls and resultant emphysema. Excess alpha1-antitrypsin in hepatocytes results in chronic liver disease. SERPINA1 gene mutation alters the configuration of the alpha1-antitrypsin molecule and prevents its release from hepatocytes. By far, the most common severe deficient variant is the Z allele, which is produced by substitution of a lysine for glutamate at position 342 of the molecule. This accounts for 95% of the clinically recognized cases of severe alpha-1 AT deficiency. On cut section of the lung, emphysematous process is evidenced by dilated air spaces and loss of lung parenchyma. Superimposed infections can result in scarring. Panacinar emphysema is commonly associated with AATD with loss of all portions of the acinus from the respiratory bronchiole to the alveoli. In alpha1-antitrypsin deficiency (AATD), the emphysematous areas are uniformly distributed throughout the lobule found more commonly in the basilar portions of the lung.
Differentiating Alpha 1-antitrypsin deficiency from Other Diseases
Alpha 1-antitrypsin deficiency has to be differentiated from other conditions with similar presentation like autoimmune hepatitis, bronchiectasis, bronchitis, chronic obstructive pulmonary disease (COPD), cystic fibrosis, emphysema, primary ciliary dyskinesia (Kartagener syndrome), and viral hepatitis.
Epidemiology and Demographics
Alpha 1-antitrypsin deficiency (A1AD) is more common in people of Northern European, Iberian, and Saudi Arabian descent. Most researchers believe it is markedly underrecognized. The incidence of AATD is estimated to be 20 cases per 100,000 individuals worldwide. The prevalence of AATD is estimated to be 70,000-100,000 cases annually. Alpha1-antitrypsin deficiency (AATD) is one of most common lethal genetic diseases among the adult white population. AATD has estimated 117 million carriers and 3.4 million affected individuals.
Risk Factors
First degree relatives of patients with known AAT deficiency are at an increased risk for the condition. Smoking is a risk factor for the development of serious lung disease in patients with AAT deficiency. The risk for lung disease also increases with exposure to dust, fumes, or other toxic substances.
Screening
According to the Spanish Society of Pneumology and Thoracic Surgery (SEPAR), all COPD patients should be screened for AATD at least once in their lifetime. All patients with an unexplained liver disease with or without accompanying respiratory symptoms should be evaluated for AATD.
Natural History, Complications, and Prognosis
If left untreated, not all patients with deficient gene develop symptomatic emphysema or cirrhosis. In symptomatic patients, the median time between observation of symptoms and diagnosis is approximately 8 years. The symptoms of alpha1-antitrypsin deficiency (AATD) in the first two decades of life are mainly of the associated liver disease progressing to pulmonary manifestations appear later in life. Emphysema, is seen in nonsmokers in the fifth decade of life and during the fourth decade of life in smokers. Less common associations are panniculitis and cytoplasmic antineutrophil cytoplasmic antibody-positive vasculitis. The most common cause of death is emphysema. Chronic liver disease is the second most common cause of death. Common complications of AATD include pneumothorax, pneumonia, acute exacerbation of airflow obstruction, and respiratory failure. Prognosis depends on how patients are identified. Patients identified as a result of screening often have an excellent prognosis. Those identified because of their symptoms have a poor prognosis.
Diagnosis
Diagnostic Criteria
A reduced concentration of serum alpha 1-antitrypsin levels is diagnostic of alpha 1-antitrypsin deficiency (AATD).
History and Symptoms
Alpha 1-antitrypsin deficiency (A1AD) may be slow to manifest in symptom onset in newborns. As patient ages, liver dysfunction will occur. The hallmark of AATD is dyspnea. A positive history of dyspnea and liver cirrhosis or chronic hepatitis is suggestive of AATD. The presentation of the disease varies depending on the type of mutation associated with AATD. Symptoms of alpha-1 antitrypsin deficiency include shortness of breath, wheezing, rhonchi and rales (may appear to be due to recurring respiratory infections), and obstructive asthma that does not respond to treatment.
Physical Examination
Physical examination of patients with AATD is usually remarkable for signs characteristic of increased respiratory work, airflow obstruction and hyperinflation that varies according to the severity of emphysema. Patients with mild emphysema usually have no abnormal findings on physical examination. Patient may appear normal. Those with severe emphysema develop tachypnea and pursed-lip breathing. Other findings on physical examination include pulsus paradoxus, scalene muscle retraction, intercostal muscle retraction, wheezing, hepatomegaly, hyperinflation results in barrel chest, increased percussion note, decreased breath sound intensity, and distant heart sounds.
Laboratory Findings
A reduced concentration of serum alpha1-antitrypsin levels is diagnostic of AATD. Laboratory findings consistent with the diagnosis of AATD include moderate-to-severe airflow obstruction with an FEV1 in the range of 30-40% of the predicted value, reduced vital capacity, increased lung volumes secondary to air trapping (residual volume >120% of predicted value) are usually present, diffusing capacity values are reduced substantially (<50% of predicted value) in most symptomatic patients. Serum alpha1-antitrypsin levels are determined by nephelometry. Serum testing is used for diagnostic testing in those patients with family histories compatible with alpha1-antitrypsin deficiency or with siblings with known alpha1-antitrypsin deficiency. In patients with clinical features that are highly suggestive of alpha1-antitrypsin deficiency but whose serum levels are within the reference range the next best step is to perform a functional assay of alpha1 antiprotease, which measures the ability of the patient’s serum to inhibit human leukocyte elastase. Perform liver function tests in patients with low or borderline levels of alpha1-antitrypsin. Measurement of serum transaminases, bilirubin, albumin, and routine clotting function (activated partial thromboplastin time and international normalized ratio).
Imaging Findings
X-ray
On chest Xray of Alpha1-antitrypsin deficiency (AATD), emphysema presents as a hyperlucent appearance because the healthy tissue has been destroyed. Affected regions can also present as oligemic areas on x-ray because they lack the normal rich pattern of branching blood vessels. A characteristic feature observed in about two thirds of PiZZ patients of alpha1-antitrypsin deficiency is that the emphysema has a striking basilar distribution. In contrast, cigarette smoking is associated with a more severe apical disease.
CT scan
On High-resolution CT (HRCT) scan of the chest, hypoattenuated areas result from a lack of lung tissue. As tissue is lost, pulmonary vessels appear smaller, fewer in number, and spread farther apart. Mild forms of alpha1-antitrypsin disease can be missed on HRCT scanning. However, when the disease is moderate, panlobular and characteristic lower zone predominance is observed. Severe forms may be indistinguishable from severe centrilobular emphysema. normal lung structures have been replaced by abnormal airspaces CT of the abdomen shows evidence of hepatomegaly or cirrhosis or hepatocellular carcinoma.
Other Diagnostic Studies
Patients with low or borderline serum levels are tested with phenotyping (serum levels < 100 mg/dL) by isoelectric focusing (IEF) is the most commonly used method to definitively detect the alpha1-antitrypsin phenotype that indicates a risk for AATD. Genotyping uses DNA extracted from circulating mononuclear blood cells that utilize DNA amplification techniques with melt-curve analysis.
Treatment
Medical Therapy
Treatment guidelines for AATD include: alpha 1 antitrypsin enzyme repletion, smoking cessation, long-acting inhaled bronchodilators, preventive vaccinations against influenza and pneumococcus, pulmonary rehabilitation for patients with functional impairment, supplemental oxygen if needed, lung transplantation, treatment of COPD exacerbation in all patients of AATD should include AAT repletion.
Surgery
Lung transplantation may be recommended for some patients with end-stage lung disease. Alpha 1-antitrypsin deficiency accounts for about 5% of all lung transplantation performed in the United States. Five year survival rates following lung transplant is approximately 50%. The rate of FEV1 decline among AATD patients who received double lung transplantation was faster than among single lung recipients. The estimated median survival time was 11 years in transplant recipients versus 5 years in controls. Lung volume reduction surgery (LVRS) can help relieve dyspnea and improve exercise capacity in patients with emphysema. Data regarding the efficacy of LVRS for individuals with AATD is limited and generally less favorable in magnitude and duration of FEV1 improvement.
Primary Prevention
Effective measures for the primary prevention of alpha 1-antitrypsin deficiency includes vaccination against hepatitis A and B is recommended to decrease the risk of liver disease.
Secondary Prevention
Secondary prevention strategies following alpha1-antitrypsin deficiency (AATD) includes avoiding cigarette smoke. Smoking accelerates the progression of emphysema in severely alpha 1 antitrypsin deficient individuals by as much as 15 years when compared to their nonsmoking controls. Pneumonia and annual influenza vaccines will help prevent respiratory infections in patients with alpha1-antitrypsin deficiency (AATD). The ATS/ERS AAT Deficiency Task Force recommends that all exacerbations with purulent sputum be treated with early antibiotic therapy. Prompt and effective treatment of infections may provide protection from additional lung injury from an influx of neutrophils into the alveolus.
Future or Investigational therapies
Treatment options for alpha 1-antitrypsin deficiency currently being studied include recombination and inhaled forms of alpha 1-antitrypsin. Other experimental therapies are aimed at the prevention of polymer formation in the liver. Gene therapy to deliver recombinant adeno-associated virus carrying the human AAT (alpha 1 antitrypsin) gene is also being investigated as an alternate treatment approach.
References
Historical Perspective
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
Alpha 1-antitrypsin deficiency (A1AD) was discovered in 1963 by Carl-Bertil Laurell (1919–2001) and Eriksson at the University of Lund, Sweden. In 1969, Sharp et al was the first to discover the association between liver disease and development of A1AD.
Historical Perspective
- In 1963, Carl-Bertil Laurell (1919–2001) and Eriksson at the University of Lund, Sweden was the first to discover A1AD at the General Hospital in Malmö, Sweden.[1][2]
- Laurell, along with a medical resident, Sten Eriksson, observed the absence of the α1 band on protein electrophoresis in samples of patients. 60% of these patients were had developed emphysema at a young age.
- In 1964, Gross described the animal model of emphysema caused by intratracheally instilled papain.
- In 1967, Fagerhol described associated allelic variation of AAT.
- In 1967, Janoff described neutrophil elastase.
- In 1969, Sharp described association with neonatal cirrhosis. Sharp et al was the first to discover the association between liver disease and development of A1AD.
References
- ↑ Laurell CB, Eriksson S (1963). “The electrophoretic alpha 1-globulin pattern of serum in alpha 1-antitrypsin deficiency”. Scand J Clin Lab Invest. 15: 132&ndash, 140.
- ↑ Sharp H, Bridges R, Krivit W, Freier E (1969). “Cirrhosis associated with alpha-1-antitrypsin deficiency: a previously unrecognized inherited disorder”. J Lab Clin Med. 73 (6): 934–9. PMID 4182334.
Classification
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
There is no established system for the classification of alpha 1-antitrypsin deficiency.
Classification
There is no established system for the classification of alpha 1-antitrypsin deficiency.
References
Pathophysiology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
Alpha 1-antitrypsin (A1AT) is synthesized and secreted mainly by hepatocytes. Alpha1-antitrypsin enzyme is a member of the serine protease inhibitor (serpin) family of proteins. Alpha 1-antitrypsin (A1AT) protects the lungs from proteases like the neutrophil elastase enzyme. A genetic mutation in the SERPINA1 gene results in decreased levels of alveolar alpha1 antitrypsin. Proteases accumulate in the alveoli causing a destruction of alveolar walls and resultant emphysema. Acculmulation of excess alpha1-antitrypsin in hepatocytes results in chronic liver disease. SERPINA1 gene mutation alters the structure of the alpha1-antitrypsin molecule and prevents its release from hepatocytes. By far, the most common severe deficient variant is the Z allele, which is produced by lysine substitution for glutamate at 342 position in the alpha 1-antitrypsin molecule. The Z allele accounts for 95% of the clinically recognized cases of severe alpha-1 AT deficiency. On cut section of the lung, emphysematous process is evidenced by dilated air spaces and loss of lung parenchyma. Superimposed infections can result in scarring. Panacinar emphysema is commonly associated with AATD with loss of all portions of the acinus from the respiratory bronchiole to the alveoli. In alpha1-antitrypsin deficiency (AATD), the emphysematous areas are uniformly distributed throughout the lobule found more commonly in the basilar portions of the lung.
Pathophysiology
The pathophysiology of alpha 1-antitrypsin deficiency (AATD) may be described as follows:[1][2][3]
- Alpha 1-antitrypsin (A1AT) is synthesized and secreted mainly by hepatocytes.
- Other sources of the enzyme include:
- Alpha1-antitrypsin enzyme is a member of the serine protease inhibitor (serpin) family of proteins.
- Functions of alpha1-antitrypsin include:
- Inhibition of pancreatic trypsin, and other proteinases including neutrophil elastase, cathepsin G and proteinase 3.
- Protection of the lungs from proteases like the neutrophil elastase enzyme.
- Genetic mutation in the SERPINA1 gene results in decreased levels of alveolar alpha1 antitrypsin.
Lung
- Proteases accumulate in the alveoli causing a destruction of alveolar walls and resultant emphysema.
- Smoking is an important risk factor in the development of the lung disease associated with alpha 1 antitrypsin deficiency.
- The protease-antiprotease imbalance in the lung has major consequences, in addition to increasing the inflammatory reaction in the airways.
- Cigarette smoke directly inactivates alpha 1-antitrypsin by oxidizing essential methionine residues to sulfoxide forms, decreasing the enzyme activity by a rate of 2000.
- In Z-variant of alpha1 antitrypsin deficiency, there is decreased levels of alpha1 antitrypsin in the lung.
- The alpha1 antitrypsin that is present is 5 times less effective than normal alpha1 antitrypsin. The residual alpha1 antitrypsin is susceptible to inactivation by oxidation of the P1 methionine residue by free radicals from leukocytes or direct oxidation by cigarette smoke.
- The Z alpha1 antitrypsin also favors the formation of polymers in the lung. Z alpha1 antitrypsin-deficient patients have excess neutrophils in lavage fluid and in tissue sections of the lung possibly related to the chemoattractant effect of an excess of leukotriene B4 (LTB4) and interleukin (IL)-8 and the polymers themselves. These circumstances of unopposed proteolytic enzyme activity and an increase in inflammatory conditions result in emphysema.
Liver
- Excess alpha1-antitrypsin in hepatocytes results in chronic liver disease.
- The Z mutation results in a conformational change in the alpha 1 antitrypsin molecule and causes most of the unstable protein to form polymers.
- Opening of the β sheet leaves it susceptible to interaction with another alpha 1 antitrypsin molecules to form a dimer or a polymer. These polymers get trapped in the endoplasmic reticulum.
- SERPINA1 gene mutation alters the configuration of the alpha1-antitrypsin molecule and prevents its release from hepatocytes. By far, the most common severe deficient variant is the Z allele, which is produced by substitution of a lysine for glutamate at position 342 of the molecule. This accounts for 95% of the clinically recognized cases of severe alpha-1 AT deficiency.
Genetics
- Alpha1-antitrypsin deficiency (AATD) is inherited in an autosomally-codominant pattern caused by mutations in the SERPINA1 gene.[4]
- Normal blood levels of alpha-1 antitrypsin are 1.5-3.5 gm/l.
- The alpha-1 AT gene is located on the long arm of chromosome 14 (gene locus:14q32.1). The SERPINA1 gene has six introns, seven axons and 12.2kb in length. There have been 120 different alleles for alpha-1 AT variants that have been described, but only 10-15 are associated with severe alpha-1 deficiency.
- Each allele has been given a letter code based upon electrophoretic mobility that varies according to protein charge from amino acid alterations on gel electrophoresis that is used to identify the PI phenotype.
- SERPINA1 gene mutation alters the configuration of the alpha1-antitrypsin molecule and prevents its release from hepatocytes. By far, the most common severe deficient variant is the Z allele, which is produced by substitution of a lysine for glutamate at position 342 of the molecule. This accounts for 95% of the clinically recognized cases of severe alpha-1 AT deficiency.
- The 75 alleles can basically be divided into four groups:
- Normal – M alleles (normal phenotype is MM), found in 90% of the U.S. population, patients have normal lung function.
- Deficient – Z allele (carried by 2-3% of the U.S. Caucasian population), have plasma levels of alpha-1 AT that is < 35% of normal.
- Null (Z) – No detectable alpha-1 AT. Least common and most severe form of the disease.
- Dysfunctional (S) – Patients have a normal alpha-1 AT level, but the enzyme does not function properly.
- The most common allele is the M allele which codes for protease inhibitor (Pi) M protein.
- The most common severe deficiency allele is the Z allele which, in the homozygous state (PiZZ).
- The S allele is associated with AAT plasma levels approximately 60% of normal in the homozygous state.
- In individuals with PiSS, PiMZ and PiSZ phenotypes, blood levels of A1AT are reduced to between 40 and 60% of normal levels, sufficient to protect the lungs from the effects of elastase in people who do not smoke.
- In individuals with the PiZZ phenotype, A1AT levels are less than 15 % of normal, and patients are likely to develop emphysema at a young age; 50 % of these patients will develop liver cirrhosis, because the A1AT is not secreted properly and instead accumulates in the liver.
- A liver biopsy of affected cases will reveal Periodic acid-Shiff (PAS)-positive, diastase-negative granules.
- Differences in speed of migration of different protein variants on gel electrophoresis have been used to identify the PI phenotype, and these differences in migration relate to variations in protein charge resulting from amino acid alterations.
- The M allele results in a protein with a medium rate of migration; the Z form of the protein has the slowest rate of migration.
- Some individuals inherit null alleles that result in protein levels that are not detectable.
- The S variant occurs at a frequency of 0.02–0.03 and is associated with mild reductions in serum AAT levels.
- The Z variant is associated with a severe reduction in serum AAT levels. The most common alleles are the M variants with allele frequencies of greater than 0.95 and normal AAT levels.
Molecular Biology
- Crystal structure of alpha1-antitrypsin enzyme is composed of three β sheets (A, B, C) and an exposed mobile reactive loop with a peptide sequence as a pseudosubstrate for the target proteinase enzyme.
- This loop consists of amino acids within this loop are the PI–PI′ residues, methionine serine, as these are binding sites for neutrophil elastase.
- The Alpha-1 antitrypsin molecule is an acute phase glycoprotein.
- Alpha-1 AT is the protease inhibitor in highest concentration in human plasma.Its functions include inhibition of trypsin and neutrophil elastase.
- Alpha-1 antitrypsin is a part of serpin class of serine protease inhibitors characterized by their unique ability to undergo a conformational change.
- Other members of the serpin class of protease inhibitors include antithrombin, C1-inhibitor, and the many inhibitors of plasminogen.
- An advantage of this molecular mobility is that it enables the inhibitor to trap its target protease form a complex that can remain stable for hours.
- The limitation is that it makes the serpins more than usually vulnerable to dysfunctional mutations.
Associated Conditions
α1-antitrypsin deficiency has been associated with a number of diseases:
- COPD
- Asthma
- Wegener’s granulomatosis
- Pancreatitis
- Gallstones
- Bronchiectasis (possibly)
- Prolapse[3]
- Primary sclerosing cholangitis
- Autoimmune hepatitis
- Emphysema
- Cancer
Gross Pathology
- On cut section of the lung, emphysematous process is evidenced by dilated air spaces and loss of lung parenchyma.
- Superimposed infections may result in scarring.
- Panacinar emphysema is commonly associated with alpha 1-antitrypsin deficiency with loss of all portions of the acinus from the respiratory bronchiole to the alveoli.
Microscopic Pathology
- Emphysema results in destruction of alveolar walls and permanent abnormal enlargement of the airspace distal to the terminal bronchiole. [5]
- In alpha1-antitrypsin deficiency (AATD), the emphysematous areas are uniformly distributed throughout the lobule found more commonly in the basilar portions of the lung.
- In contrast, emphysema resulting from cigarette smoking characteristically involves the centrilobular lung and respiratory bronchioles in the central portion of the lobule, initially at the apex of the lung.
References
- ↑ Stoller JK, Aboussouan LS (2012). “A review of α1-antitrypsin deficiency”. Am. J. Respir. Crit. Care Med. 185 (3): 246–59. doi:10.1164/rccm.201108-1428CI. PMID 21960536.
- ↑ Stoller JK, Brantly M (2013). “The challenge of detecting alpha-1 antitrypsin deficiency”. COPD. 10 Suppl 1: 26–34. doi:10.3109/15412555.2013.763782. PMID 23527684.
- ↑ Stoller JK (2016). “Alpha-1 antitrypsin deficiency: An underrecognized, treatable cause of COPD”. Cleve Clin J Med. 83 (7): 507–14. doi:10.3949/ccjm.83a.16031. PMID 27399863.
- ↑ “The genetics of α1-antitrypsin: a family study in England and Scotland – COOK – 1975 – Annals of Human Genetics – Wiley Online Library”.
- ↑ Greene DN, Elliott-Jelf MC, Straseski JA, Grenache DG (2013). “Facilitating the laboratory diagnosis of α1-antitrypsin deficiency”. Am. J. Clin. Pathol. 139 (2): 184–91. doi:10.1309/AJCP6XBK8ULZXWFP. PMID 23355203.
Causes
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
Alpha1-antitrypsin deficiency (AATD) is caused by a mutation in the SERPINA1 gene. SERPINA1 is located on chromosome 14.
Causes
- Alpha1-antitrypsin deficiency (AATD) is caused by a mutation in the SERPINA1 gene.[1][2]
- SERPINA1 is located on chromosome 14 and is highly pleomorphic, with more than 100 allelic variants.This gene instructs the body to make a protein called alpha-1 antitrypsin (AAT), which functions to inhibit neutrophil elastase enzyme.
- Neutrophil elastase helps the body fight infections, but it can also attack healthy tissue in the lung if not inactivated by AAT. Alpha1-antiprotease functions to protect the lungs from unregulated protease activity.
- Mutations associated with AAT can result in:
- Deficient amount of AAT in the body.
- Complete absence of AAT.
- A form of AAT that does not work effectively to protect healthy lung tissue.
- SERPINA1 mutation allows neutrophil elastase to destroy lung tissue, causing lung disease.
- In addition, the accumulation of intrahepatic alpha1-antitrypsin can build up in the liver and can result in apoptosis of hepatocytes.
- The severity of AATD may also be worsened by environmental factors such as exposure to tobacco smoke, dust, and chemicals. This initially presents as laboratory abnormalities on liver function test, but can progress to hepatitis, followed by fibrosis and cirrhosis.
References
- ↑ Hazari YM, Bashir A, Habib M, Bashir S, Habib H, Qasim MA, Shah NN, Haq E, Teckman J, Fazili KM (2017). “Alpha-1-antitrypsin deficiency: Genetic variations, clinical manifestations and therapeutic interventions”. Mutat. Res. 773: 14–25. doi:10.1016/j.mrrev.2017.03.001. PMID 28927525.
- ↑ Stoller JK (2016). “Alpha-1 antitrypsin deficiency: An underrecognized, treatable cause of COPD”. Cleve Clin J Med. 83 (7): 507–14. doi:10.3949/ccjm.83a.16031. PMID 27399863.
Differentiating Alpha 1-antitrypsin deficiency from other Diseases

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
Alpha 1-antitrypsin deficiency has to be differentiated from other conditions with similar presentation like autoimmune hepatitis, bronchiectasis, bronchitis, chronic obstructive pulmonary disease (COPD), cystic fibrosis, emphysema, primary ciliary dyskinesia (Kartagener Syndrome), viral hepatitis.
Differentiating Alpha 1-antitrypsin deficiency from Other Diseases
Alpha 1-antitrypsin deficiency presents with symptoms of emphysema associated with compromised liver function tests and/or cirrhosis. Differential diagnosis of jaundice and RUQ pain includes:
Jaundice and RUQ pain differential diagnosis are:
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The differential diagnosis of jaundice, fever, and RUQ pain are:
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Differential diagnosis of cough with wheezes is :
| Diseases | Symptoms | Signs | Diagosis | |||||
|---|---|---|---|---|---|---|---|---|
| Fever | Cough | Chest pain | Wheezes | Crackles | Tachypnea | Lab tests | Imaging | |
| Asthma | – | Dry/Productive | – | + | – | + |
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| Bronchiolitis | +/- | Dry | – | + | + | +/- |
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| COPD | + | Productive | – | + | + | + |
|
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| Bacterial pneumonia | + | Productive | + | + | + | +/- |
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| Cystic Fibrosis | +/- | Productive | +/- | – | – | + | Cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction evidenced by :
|
X-ray :
Hyperinflation presents as:
Abdominal findings include dilated multiple loops of the small bowel are seen in neonatal meconium ileus. |
| Emphysema | +/- | Productive | – | + | +/- | + |
|
Chest X-ray reveals signs of emphysema include:
|
| Primary Ciliary Dyskinesia (Kartagener Syndrome) | +/- | Productive | – | + | + | + |
|
Chest X-ray reveals :
|
| Alpha 1-antitrypsin deficiency | +/- | Productive | – | + | + | + |
|
Chest X-ray Alpha1-antitrypsin deficiency (AATD) emphysema presents as:
|
AATD can present as neonatal jaundice. The differential diagnosis for neonatal jaundice is: [3]
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References
- ↑ Ghanei M, Tazelaar HD, Chilosi M, Harandi AA, Peyman M, Akbari HM; et al. (2008). “An international collaborative pathologic study of surgical lung biopsies from mustard gas-exposed patients”. Respir Med. 102 (6): 825–30. doi:10.1016/j.rmed.2008.01.016. PMID 18339530.
- ↑ Lazović B, Svenda MZ, Mazić S, Stajić Z, Delić M (2013). “Analysis of electrocardiogram in chronic obstructive pulmonary disease patients”. Med Pregl. 66 (3–4): 126–9. PMID 23653989.
- ↑ Fargo MV, Grogan SP, Saguil A (2017). “Evaluation of Jaundice in Adults”. Am Fam Physician. 95 (3): 164–168. PMID 28145671.
Epidemiology and Demographics
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
Alpha 1-antitrypsin deficiency (A1AD) is more common in people of Northern European, Iberian, and Saudi Arabian descent. Most researchers believe it is markedly underrecognized. The incidence of alpha 1-antitrypsin deficiency (A1AD) is estimated to be 20 cases per 100,000 individuals worldwide. The prevalence of alpha 1-antitrypsin deficiency AATD is estimated to be 70,000-100,000 cases annually. Alpha1-antitrypsin deficiency (AATD) is one of most common lethal genetic diseases among adult white population. Alpha1-antitrypsin deficiency AATD has estimated 117 million carriers and 3.4 million affected individuals. AATD is more prevalent among the white population. Alpha 1-antitrypsin deficiency (A1AD) is more common in people of Northern European, Iberian, and Saudi Arabian descent. Most researchers believe it is markedly under-recognized. Men and women are affected equally by AATD.
Epidemiology and Demographics
Epidemiology and demographic details of alpha 1-antitrypsin deficiency are as follows:[1][2][3]
In a recent survey, the average time interval between the onset of pulmonary symptoms and time of diagnosis was 7.2 years. About 43% of patients see at least 3 physicians before the diagnosis is established, and 12% see between 6 and 10. Thus, most authors believe that alpha-1 AT deficiency is markedly under-recognized. Because there are genetic implications to the next generation, that diagnosis can assist in smoking prevention / cessation.
Incidence
The incidence of AATD is estimated to be 20 cases per 100,000 individuals worldwide.
Prevalence
The prevalence of AATD is estimated to be 10,000 per 100,000 patients annually. Alpha1-antitrypsin deficiency (AATD) is one of most common lethal genetic diseases among adult white population. AATD has estimated 117 million carriers and 3.4 million affected individuals.
Race
AATD is more prevalent among the white population. Alpha 1-antitrypsin deficiency (A1AD) is more common in people of Northern European, Iberian, and Saudi Arabian descent. Most researchers believe it is markedly under-recognized.
Sex
Men and women are affected equally by AATD.
Age
- Alpha 1-antitrypsin deficiency is usually first diagnosed among nonsmokers in the fifth decade of life and during the fourth decade of life in smokers.
- Alpha 1-antitrypsin deficiency can present in neonates as a cause of neonatal jaundice and hepatitis.In infants it can cause cholestatic jaundice and in children, hepatic cirrhosis or liver failure.
- AATD is also the leading condition requiring liver transplantation in children.
References
- ↑ Stoller JK, Aboussouan LS (2012). “A review of α1-antitrypsin deficiency”. Am. J. Respir. Crit. Care Med. 185 (3): 246–59. doi:10.1164/rccm.201108-1428CI. PMID 21960536.
- ↑ Stoller JK, Brantly M (2013). “The challenge of detecting alpha-1 antitrypsin deficiency”. COPD. 10 Suppl 1: 26–34. doi:10.3109/15412555.2013.763782. PMID 23527684.
- ↑ Greene DN, Elliott-Jelf MC, Straseski JA, Grenache DG (2013). “Facilitating the laboratory diagnosis of α1-antitrypsin deficiency”. Am. J. Clin. Pathol. 139 (2): 184–91. doi:10.1309/AJCP6XBK8ULZXWFP. PMID 23355203.
Risk Factors
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
First degree relatives of patients with known AAT deficiency are at an increased risk for the condition. Smoking is risk factor for development of serious lung disease in patients with AAT deficiency. Risk for lung disease also increases with exposure to dust, fumes, or other toxic substances.
Risk Factors
Risk factors associated with development of alpha 1-antitrypsin deficiency are as follows:[1][2]
- First degree relatives of patients with known AAT deficiency are at an increased risk of inheriting the disorder.
- Smoking is risk factor for development of serious lung disease in patients with AAT deficiency.
- Risk for lung disease also increases with exposure to dust, fumes, or other toxic substances.
References
- ↑ Kalfopoulos M, Wetmore K, ElMallah MK (2017). “Pathophysiology of Alpha-1 Antitrypsin Lung Disease”. Methods Mol. Biol. 1639: 9–19. doi:10.1007/978-1-4939-7163-3_2. PMID 28752442.
- ↑ Stoller JK, Aboussouan LS (2012). “A review of α1-antitrypsin deficiency”. Am. J. Respir. Crit. Care Med. 185 (3): 246–59. doi:10.1164/rccm.201108-1428CI. PMID 21960536.
Screening
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
According to the Spanish Society of Pneumology and Thoracic Surgery (SEPAR), all COPD patients should be screened for AATD at least once in their lifetime. All patients with unexplained liver disease with or without respiratory symptoms should be evaluated for AATD.
Screening
Screening for alpha 1-antitrypsin deficiency includes:[1][2]
- According to the Spanish Society of Pneumology and Thoracic Surgery (SEPAR), all COPD patients should be screened for AATD at least once in their lifetime.
- All patients with unexplained liver disease with or without respiratory symptoms should be evaluated for AATD.
- Adults with necrotizing panniculitis should be screened.
References
- ↑ Hersh CP (2017). “Diagnosing alpha-1 antitrypsin deficiency: the first step in precision medicine”. F1000Res. 6: 2049. doi:10.12688/f1000research.12399.1. PMC 5710307. PMID 29225784.
- ↑ Lascano JE, Campos MA (2017). “The important role of primary care providers in the detection of alpha-1 antitrypsin deficiency”. Postgrad Med. 129 (8): 889–895. doi:10.1080/00325481.2017.1381539. PMID 28929906.
Natural History, Complications and Prognosis
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]
Overview
If left untreated, not all patients with deficient gene develop symptomatic emphysema or cirrhosis. In symptomatic patients, the median time between observation of symptoms and diagnosis is approximately 8 years. The symptoms of alpha1-antitrypsin deficiency (AATD) in the first two decades of life are mainly of associated liver disease progressing to pulmonary manifestations appear later in life. Emphysema is seen in non-smokers in the fifth decade of life and during the fourth decade of life in smokers. Less common associations are panniculitis and cytoplasmic antineutrophil cytoplasmic antibody‒positive vasculitis. The most common cause of death is emphysema. Chronic liver disease is the second most common cause of death. Common complications of AATD include pneumothorax, pneumonia, acute exacerbation of airflow obstruction, respiratory failure. Prognosis depends on how patients are identified. Patients identified as a result of screening often have excellent prognosis. Those identified because of their symptoms have poor prognosis.
Natural History
- If left untreated, not all patients with deficient gene develop symptomatic emphysema or cirrhosis.
- In symptomatic patients, the median time between observation of symptoms and diagnosis is approximately 8 years.[1][2][3]
- The symptoms of alpha1-antitrypsin deficiency (AATD) in the first two decades of life are mainly of associated liver disease progressing to pulmonary manifestations appear later in life.
- Emphysema, is seen in nonsmokers in the fifth decade of life and during the fourth decade of life in smokers.
- Less common associations are panniculitis and cytoplasmic antineutrophil cytoplasmic antibody‒positive vasculitis.
- FEV1 decreases in patients with PiZZ genotype at 51-317 mL per year compared to an estimated decline in healthy individuals at 30 mL/y.
- AATD can be seen in neonates as a cause of neonatal jaundice and hepatitis.
- It may present in infants as cholestatic jaundice and in children as liver cirrhosis or hepatic failure.
- AATD is the leading condition requiring liver transplantation in children.
- PiZZ patients have a 16% likelihood of surviving to age 60 years compared to an 85% likelihood for the general US population.
- The most common cause of death is emphysema. Chronic liver disease is the second most common cause of death.
- Respiratory failure accounts for about 62% of deaths, and complications of chronic liver disease for approximately 13%.
- The mean age of death is 50 years old for nonsmokers and 40 years old for smokers, with only 16% surviving to 60 years old compared to about 85% surviving to 65 years old in the general population.
- Mortality is directly related to FEV1 (forced expiratory volume), and rises exponentially as FEV1 falls below 35% predicted.
Complications
Common complications of AATD include:[3]
- Pneumothorax
- Pneumonia
- Acute exacerbation of airflow obstruction
- Respiratory failure
- Bronchiectasis
- Cirrhosis or liver failure
- Emphysema
- Liver cancer
Prognosis
Prognosis depends on how patients are identified. Patients identified as a result of screening often have excellent prognosis. Those identified because of their symptoms have poor prognosis.[1][2][3]
Features associated with poor prognosis include:
- Severe degree of airflow obstruction:
- FEV1 >50% has a 5-year mortality rate at 4%
- FEV1 within range 35-49% has 5-year mortality rate at 12%
- FEV1 <35 has a 5-year mortality rate at 50%
- A bronchodilator response greater than >12%
- Smoking
- Male sex
References
- ↑ 1.0 1.1 Brantly ML, Paul LD, Miller BH, Falk RT, Wu M, Crystal RG (1988). “Clinical features and history of the destructive lung disease associated with alpha-1-antitrypsin deficiency of adults with pulmonary symptoms”. Am. Rev. Respir. Dis. 138 (2): 327–36. doi:10.1164/ajrccm/138.2.327. PMID 3264124.
- ↑ 2.0 2.1 “Survival and FEV1 decline in individuals with severe deficiency of alpha1-antitrypsin. The Alpha-1-Antitrypsin Deficiency Registry Study Group”. Am. J. Respir. Crit. Care Med. 158 (1): 49–59. 1998. doi:10.1164/ajrccm.158.1.9712017. PMID 9655706.
- ↑ 3.0 3.1 3.2 Stoller JK, Tomashefski J, Crystal RG, Arroliga A, Strange C, Killian DN, Schluchter MD, Wiedemann HP (2005). “Mortality in individuals with severe deficiency of alpha1-antitrypsin: findings from the National Heart, Lung, and Blood Institute Registry”. Chest. 127 (4): 1196–204. doi:10.1378/chest.127.4.1196. PMID 15821195.
Diagnosis
Diagnosis
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Treatment
Treatment
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