Alpha-1-antitrypsin deficiency

Radswiki et al.

Alpha-1-antitrypsin (AAT) deficiency is a hereditary metabolic disorder and is the most common genetic cause of emphysema and metabolic liver disease in children. It results in the unopposed action of neutrophil elastase and subsequent severe basal pan lobular emphysema and respiratory symptoms. Accumulation of altered A1AT in hepatocytes incites inflammatory response and chronic liver disease. 

Clinical presentation

The classic presentation of the disease is with dyspnoea in the 4th to 5th decades of life. Two-thirds of individuals show clinical features but most carriers are asymptomatic.

Pathology

AAT is a protein that prevents enzymes such as elastase from degrading normal host tissue. Over 90% of the AAT protein is produced in hepatocytes by codominant gene expression on chromosome 14. The AAT protein inhibits neutrophil elastase. In patients with severe deficiency, the neutrophil elastase acts unopposed resulting in damage to the lower respiratory tract. This damage is predominantly basal because of the gravitational distribution of pulmonary blood flow. 

Associations
Complications

Radiographic features

Thoracic manifestations
Plain radiograph and CT
Nuclear medicine

Reduced perfusion and ventilation in the lower zones on a V/Q study. 

Abdominal manifestations

Hepatic manifestations of this disease are those of cirrhosis.

Treatment and prognosis

Emphysema and cirrhosis are usually considered the most common causes of death 8.

Survival is substantially worse in smokers, who have a 20-year decrease in longevity relative to non-smokers. According to one study, the overall median survival time was ~ 55 years 7.

AAT replacement therapy, most often by weekly intravenous infusions of AAT purified from human plasma, has been used in some situations to partially correct the biochemical defect 14-15.  

While randomised, placebo-controlled clinical trials have confirmed a reduction in the decline in lung density in patients receiving augmentation therapy 14. It's efficacy in reducing mortality, however, is uncertain 16. Other management strategies include avoidance of smoking and other risk factors for cirrhosis.

Differential diagnosis

The differential will depend on the organ involved:

Share Article

Article Information

rID: 11131
Systems: Chest, Hepatobiliary
Section: Pathology
Tag: emphysema
Synonyms or Alternate Spellings:
  • α1-Antitrypsin deficiency
  • Alpha 1 AT deficiency
  • alpha-1-antitrypsin (AAT) deficiency
  • Alpha-1-antitrypsin deficiency
  • α1-Antitrypsin deficiency (AATD)
  • PiZZ
  • alpha antitrypsin deficiency

Support Radiopaedia to see fewer ads

  • Drag
    Case 1
    Drag here to reorder.
  • Drag
    Case 1: lateral radiograph
    Drag here to reorder.
  • Drag
    Emphysema

Hyper-...
    Case 2
    Drag here to reorder.
  • Drag
    Pan-lobular emphy...
    Case 2: with CT showing pan-lobular emphysema
    Drag here to reorder.
  • Drag
    Case 3
    Drag here to reorder.
  • Drag
    Case 4: probable
    Drag here to reorder.
  • Drag
    Case 5
    Drag here to reorder.
  • Updating… Please wait.
    Loadinganimation

    Alert accept

    Error Unable to process the form. Check for errors and try again.

    Alert accept Thank you for updating your details.