Alpha-1 Antitrypsin Deficiency

The disease is related to the following processes:  heriditary and has an incidence of about  2 / 100.000.

Overview

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder that occurs due to absence of alpha–1 antitrypsin (AAT) enzyme. This heritable disorder predisposes an individual to fall prey to an array of clinical diseases especially early onset emphysema [1]. However, the lungs and the liver are the two main organs that are severely affected. The effects of AATD are not evident until one is of 30 years of age [2].

There is no cure to this disease. The symptoms can however be managed with an effective treatment regime. An estimated 1-5% of adults with chronic obstructive pulmonary disease (COPD) may have AAT deficiency [3]. Although adults AATD cases are more predisposed to emphysema, cases of children with AAT deficiency presenting with emphysema symptoms may occur rarely [4].

Etiology

Alpha–1 antitrypsin deficiency is a genetic disorder. If a child inherits two AAT genes from both the parents, then he is said to have developed the AAT deficiency.

The faulty AAT gene that is known to cause the genetic disorder is known as PiZ. Now, if the child inherits one normal AAT gene and one faulty AAT gene (Piz) then he would not suffer from AAT deficiency. However, in such cases, there is a possibility that the child transfers the faulty PiZ gene to the next generation.

Epidemiology

About 1.1 million individuals across the globe fall prey to this genetic disease. Earlier it was thought that AAT deficiency is only the disease of Caucasians. However, with in depth research it was revealed that this inherited genetic disorder exists amongst all racial groups. It has also been estimated, that about 3.1 million Americans suffer from COPD.

Of these about 1.9% individuals suffer from COPD as a result of AAT deficiency. Statistics have also revealed that about 1 in every 3000 to 5000 individuals of UK suffer from AAT deficiency. Of the 100,000 person with AAT deficiency in the world only less than 10% are identified clinically [5].

The median time from the instance the symptoms were observed to the time of clinical diagnosis is 8 years making mortality rate for symptomatic patients very high [6].

Sex distribution
Age distribution

Pathophysiology

AAT deficiency is an inherited autosomal disorder that occurs due to mutations in a specific gene that is known to alter the configuration of the alpha–1 antitrypsin molecule. This specific gene is named as SERPINA1 and is located in the long arm of chromosome 14. Alteration of the configuration of AAT prevents its release from the hepatocytes causing a significant decrease in its serum levels. This sequence of events gives rise to the condition related to AAT deficiency.

Prognosis

The prognosis of the disease condition varies with the degree of symptoms and the pace at which the disease progresses. However, with prompt diagnosis and effective treatment regime, individuals are thought to recover well. The progression of the disease can be arrested and the symptoms put to rest. Since this is an inherited disease condition, it cannot be cured but managed well with appropriate treatment.

Complications

If timely diagnosis and treatment is not initiated, then AAT deficiency can bring along life threatening complications. These include:

Presentation

In many cases, signs and symptoms of AAT deficiency do not show up before the individual is above the age of 30 years. However, some individuals who smoke tend to develop symptoms in their early 20s. AAT deficiency gravely affects the functioning of the lungs and the liver. The signs and symptoms include the following:

  • Shortness of breath
  • Wheezing
  • Cough along with sputum
  • Chest infections
  • Mild liver damage 
  • Vision problems
  • Unexplained weight loss
  • Fatigue 
  • Rapid heart rate upon standing

Workup

The condition of AATD is usually diagnosed when an individual complains of shortness of breath or is suffering from lung or liver disorders. Lung and liver disease are the preliminary features of AATD.

Blood test to determine the levels of AAT is carried out. In addition, a phenotype blood test is also done to assess the presence of the causing gene. Several other diagnostic tests such as lung functioning tests known as spirometry are done to evaluate the functioning ability of the lungs.

Imaging studies that include an X-ray and CT scan of the chest is also done to further understand the capacity of the lungs. CT scan of the chest would reveal whether the patient has emphysema and its degree of severity. Liver function tests may also be done in order to assess the functioning of the organ.

Treatment

So far there is no known treatment plan to cure this genetic disorder. Treatment methods are designed to effectively manage the disease condition and slow down the progression of the disease. Medications form the primary basis of the treatment program.

The individual is put on drugs such as a steroids and bronchodilators to help manage the inflammation and flare-ups of emphysema.

Antibiotics may also have to be prescribed if the individual is also suffering from infection of the chest. Theophylline that works as a bronchodilator is also prescribed to patients.

Augmentation therapy with intravenous alpha-1 antitrypsin protein may afford some benefits for patients with low levels of AAT below 11 µM [8].

Surgery is often the last resort when the patients with COPD develop bullae characterized by large air–filled sacs. Liver transplantation may be required among patients with cirrhosis due to AAT deficiency [9].

Immunizations shots are also given to individuals with emphysema. Some individuals may also be advised to undergo home oxygen therapy. Individuals with recurrent bouts of emphysema may benefit from this. Portable oxygen cylinders are available and oxygen is supplied either through tubes or masks.

Prevention

AAT being an inherited disorder has no prevention. However, early detection of this disease can help in better management of the disease condition. If parents suffer from the same, then diagnosis of their children at an early age can help early initiation of treatment. Making small changes in lifestyle can go a long way in better management of the disease condition. The following practices can be adopted:

  • The practice of smoking cigarettes should be discontinued. It not only aggravates the existing condition but also speeds up the development of signs and symptoms of the disease.
  • Alcohol should be avoided as it would further aggravate the condition in individuals suffering from liver disease as a secondary complication of AAT.
  • The administration of pneumococcal and influenza vaccination have significantly lowered the incidence of emergency room visits of AAT deficient patients with clinical emphysema [10].

Patient Information

Definition

Alpha-1 antitrypsin (AATD) deficiency is an inherited genetic disorder caused due to deficiency of the alpha–1 antitrypsin. This disorder generally affects the lungs and liver of the individual. So far there is no cure to this disease, but with appropriate treatment regime, the symptoms can be managed and the progression of the condition slowed down.

Cause

Two faulty genes of AATD are responsible for the causation of the disease condition. These faulty genes are known as PiZ. If the individual inherits one faulty gene and one normal then he would not develop AATD; however he may pass on the faulty gene to his children.

Symptoms

AATD generally presents lung and liver disorders. Coughing, wheezing, shortness of breath, chest infection, fatigue and unexplained weight loss are some of the grave symptoms of this genetic disorder.

Diagnosis

The condition is usually diagnosed through blood tests that detect the level of alpha–1 antitrypsin. In addition spirometry is also done to assess the lung functioning. Imaging studies that include X-ray and CT scan of the chest are done to evaluate emphysema.

Treatment

Treatment of AATD includes medications that are given to control the wheezing and coughing problem. Antibiotics and steroids are administered to combat the infection and bring down the inflammation.

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References

  1. Stoller JK, Aboussouan LS. A review of a1-antitrypsin deficiency. Am J Respir Crit Care Med. Feb 1 2012; 185(3):246-59.
  2. Kauppi P, Jokelainen K. Alpha-1 antitrypsin deficiency. Duodecim. 2011; 127(18):1911-8 (ISSN: 0012-7183)
  3. Marciniuk DD, Hernandez P, Balter M, Bourbeau J, Chapman KR, Ford GT, et al. Alpha-1 antitrypsin deficiency targeted testing and augmentation therapy: a Canadian Thoracic Society clinical practice guideline. Can Respir J. Mar-Apr 2012; 19(2):109-16.
  4. Stoller JK, Lacbawan FL, Aboussouan LS. Alpha-1 Antitrypsin Deficiency. 1993
  5. Greene DN, Elliott-Jelf MC, Straseski JA, Grenache DG. Facilitating the laboratory diagnosis of a1-antitrypsin deficiency. Am J Clin Pathol. Feb 2013; 139(2):184-91.
  6. Bornhorst JA, Greene DN, Ashwood ER, Grenache DG. A1-Antitrypsin phenotypes and associated serum protein concentrations in a large clinical population. Chest. Apr 2013; 143(4):1000-8.
  7. Serapinas D, Obrikyte V, Vaicius D, Balciuviene R, Valavicius A, Sakalauskas R. Alpha-1 antitrypsin deficiency and spontaneous pneumothorax: possible causal relationship. Pneumologia. 2014; 63(1):32-5 (ISSN: 2067-2993)
  8. Campos MA, Lascano J. a1 Antitrypsin deficiency: current best practice in testing and augmentation therapy.Ther Adv Respir Dis. Jul 9 2014
  9. Carey EJ, Iyer VN, Nelson DR, Nguyen JH, Krowka MJ. Outcomes for recipients of liver transplantation for alpha-1-antitrypsin deficiency–related cirrhosis. Liver Transpl. 2013; 19(12):1370-6 (ISSN: 1527-6473)
  10. Köhnlein T, Janciauskiene S, Welte T. Diagnostic delay and clinical modifiers in alpha-1 antitrypsin deficiency. Ther Adv Respir Dis. 2010; 4(5):279-87 (ISSN: 1753-4666)

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