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Alpha-1 Antitrypsin Deficiency (AATD)

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Alpha-1 Antitrypsin Deficiency (AATD)

Alpha-1 Antitrypsin Deficiency :An inherited genetic disorder causing low levels of alpha-1 antitrypsin (AAT), a protein that protects lung tissue from neutrophil elastase. Its deficiency leads to early-onset emphysema (especially in the lower lobes) and may also cause liver disease.

Also called

Alpha-1 proteinase inhibitor deficiency

ICD-10

E88.01

Specialty

Pulmonology

Onset

Chronic

Reviewed

July 2026

On This Page

Overview

Alpha-1 Antitrypsin is a protein mainly produced by the liver. It protects the lungs from destructive enzymes, especially neutrophil elastase.

Deficiency causes:

  • Lungs: Loss of protection → Alveolar destruction → Emphysema
  • Liver: Abnormal AAT accumulation → Liver injury
  •  

Etiology & Risk Factors

Causes of Alpha-1 Antitrypsin Deficiency

Alpha-1 Antitrypsin Deficiency is caused by mutations in the SERPINA1 gene.

Inheritance

  • Autosomal codominant

Important Alleles

  • M allele: Normal
  • Z allele: Most important severe deficiency allele
  • S allele: Causes milder deficiency

Severe Disease

The PiZZ genotype is strongly associated with severe AAT deficiency.

Risk Factors for Lung Disease

  • Cigarette smoking
  • Occupational dust exposure
  • Air pollution
  • Recurrent respiratory infections

Important Note

Smoking greatly accelerates lung damage in patients with Alpha-1 Antitrypsin Deficiency

Pathophysiology

Lung Disease

SERPINA1 mutation
⬇
↓ Functional alpha-1 antitrypsin
⬇
Unopposed neutrophil elastase activity
⬇
Destruction of alveolar walls
⬇
Loss of elastic recoil
⬇
Emphysema + Persistent airflow obstruction

Liver Disease

Abnormal AAT protein production
⬇
Protein accumulation inside hepatocytes
⬇
Liver cell injury
⬇
Fibrosis
⬇
Cirrhosis and possible liver cancer

Key Concept

Lung disease results from protein deficiency, while liver disease results from abnormal protein accumulation.

Clinical Presentation

  1. Respiratory Features

    • Progressive dyspnea
    • Wheezing
    • Chronic cough
    • Sputum production
    • Reduced exercise tolerance
    • Recurrent respiratory infections
    • Early-onset emphysema

    Typical Lung Pattern

    Emphysema often:

    • Develops at a younger age
    • Is worse in smokers
    • Predominantly affects the lower lungs

    Liver Features

    • Neonatal jaundice
    • Elevated liver enzymes
    • Chronic hepatitis
    • Cirrhosis
    • Liver failure

    Other Features

    • Panniculitis — rare
    • Granulomatosis with polyangiitis association

History Taking

    • Ask about:

      • Shortness of breath?
      • Chronic cough?
      • Wheezing?
      • Exercise limitation?
      • Age when symptoms started?
      • Smoking history?
      • Occupational exposure?
      • Previous diagnosis of COPD or emphysema?
      • Liver disease or jaundice?
      • Family history of emphysema?
      • Family history of liver disease?
      • Previous AAT testing?

Physical Examination

  • Respiratory Examination

    Look for:

    • Tachypnea
    • Prolonged expiration
    • Pursed-lip breathing
    • Hyperinflated chest
    • Reduced breath sounds
    • Wheezing

    Advanced Lung Disease

    • Cyanosis
    • Accessory muscle use
    • Reduced oxygen saturation

    Liver Examination

    Look for:

    • Jaundice
    • Hepatomegaly
    • Splenomegaly
    • Ascites
    • Signs of chronic liver disease

Investigations

  • Serum Alpha-1 Antitrypsin Level — Initial Test

    A low serum AAT level suggests the diagnosis.

    Genotyping or Phenotyping

    Used to:

    • Confirm the diagnosis
    • Identify the specific AAT variant
    • Assess disease risk

    Pulmonary Function Tests

    May show:

    • Obstructive airflow pattern
    • Reduced FEV₁/FVC ratio
    • Reduced gas transfer

    Chest CT

    May show:

    • Emphysema
    • Predominantly lower-lung involvement

    Liver Assessment

    • Liver function tests
    • Liver ultrasound
    • Other fibrosis assessment when indicated

Diagnosis

  • Diagnosis is based on:

    1. Reduced Serum AAT Level

    Together with:

    2. Confirmation of the Abnormal Variant

    Using:

    • Genotyping
    • Phenotyping

    Important Note

    AAT levels alone may be misleading because alpha-1 antitrypsin can increase during inflammation.

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Management

Alpha-1 Antitrypsin Deficiency (AATD) · Management

AATD = GENETIC DEFICIENCY OF A SERINE PROTEASE INHIBITOR — DUAL ORGAN DISEASE Alpha-1 antitrypsin (AAT) normally inhibits neutrophil elastase in the lung → deficiency causes uncontrolled proteolysis → early-onset panacinar emphysema. In the liver, misfolded Z-protein accumulates in hepatocytes → cirrhosis. Most common severe genotype: PiZZ. Management is organ-specific plus augmentation therapy where eligible.
Core Management Pillars
1
Eliminate Triggers
Absolute smoking cessation — single most important intervention; smoking accelerates lung destruction dramatically in AATD. Avoid occupational dust/fumes.
Immediate, all patients
2
Lung Disease Management
Same as COPD — bronchodilators, pulmonary rehab, vaccinations, inhaled corticosteroids if asthmatic overlap. Augmentation therapy if eligible.
Lung-targeted
3
Augmentation Therapy
IV infusion of pooled human AAT protein — raises serum and lung AAT levels above protective threshold. Slows emphysema progression. Only for lung disease; not liver disease.
Disease-modifying
4
Liver & Systemic Care
Monitor liver function, screen for fibrosis/cirrhosis, manage portal hypertension. Liver transplantation cures the genetic defect. Family screening and genetic counselling.
Organ-specific
Treatment Indication / Details Notes
Smoking Cessation All patients — absolute priority Smokers with AATD lose lung function 5–10x faster than non-smokers. Varenicline, NRT, behavioural support. No other intervention is as effective.
AAT Augmentation Therapy IV Prolastin / Respreeza (human pooled AAT) weekly Indicated for PiZZ (or other severe genotypes) with established airflow obstruction (FEV1 35–65% predicted in most guidelines). Slows CT density loss (emphysema marker). Does not help liver disease. Lifelong weekly infusion.
Bronchodilators LABA + LAMA (e.g. formoterol + tiotropium) Same as COPD management — mainstay for symptomatic airflow obstruction. SABA as reliever. LABA/LAMA combination preferred for moderate-severe disease.
Inhaled Corticosteroids ICS + LABA if frequent exacerbations or asthmatic overlap Not recommended routinely in pure emphysematous AATD. Consider triple therapy (ICS/LABA/LAMA) only in exacerbation-prone patients or eosinophilic phenotype.
Pulmonary Rehabilitation MRC dyspnoea grade ≥3 Improves exercise capacity, quality of life, and reduces exacerbations. All patients with symptomatic lung disease should be referred.
Vaccinations All patients Annual influenza, pneumococcal (PCV13 + PPSV23), COVID-19, hepatitis A and B (especially if liver disease present).
Long-term Oxygen Therapy (LTOT) PaO2 ≤7.3 kPa or SpO2 ≤88% at rest Criteria same as COPD-related LTOT. ≥15 hours/day. Reduces pulmonary hypertension and improves survival in hypoxaemic patients.
Liver Transplantation End-stage liver disease Curative for the genetic defect — the donor liver produces normal AAT. Post-transplant serum AAT normalises. Does not reverse pre-existing lung damage but prevents further liver-mediated Z-protein accumulation.
Lung Transplantation End-stage emphysema (FEV1 <25%) Bilateral lung transplant preferred. Corrects lung disease but does not alter underlying genetic defect — recipient still produces Z-protein from native liver. Augmentation therapy stops post-transplant.
Liver Monitoring Annual LFTs, ultrasound ± fibroscan All PiZZ patients need annual liver surveillance. Ursodeoxycholic acid and alcohol avoidance. Refer to hepatology if fibrosis/cirrhosis detected. Screen for hepatocellular carcinoma if cirrhotic.
Family Screening & Genetic Counselling All index cases Autosomal codominant inheritance. Screen first-degree relatives with serum AAT level + Pi genotyping. Offer genetic counselling re: reproductive implications. Register with national AATD registry where available.
Routine Monitoring
Spirometry — every 6–12 months; FEV1 trajectory guides augmentation eligibility and transplant listing
Serum AAT level — at diagnosis and to confirm adequacy of augmentation (target trough >11 μmol/L)
Annual LFTs + liver ultrasound — all PiZZ patients regardless of liver symptoms
CT chest (HRCT) — baseline; CT densitometry is gold standard for tracking emphysema progression
6-minute walk test — functional status monitoring and pre-transplant assessment
SpO2 at rest and exercise — to identify LTOT need early
Emerging & Future Therapies
Inhaled AAT — direct delivery to the lung; trials ongoing; avoids weekly IV infusion burden
Small molecule chaperones — correct Z-protein misfolding in hepatocytes, prevent liver accumulation; phase II/III trials
RNA interference (RNAi) / siRNA — suppress Z-AAT production in the liver; fazirsiran in clinical trials showing significant hepatic Z-AAT reduction
Gene therapy — AAV-mediated AAT gene delivery to liver/muscle; early phase trials; potential single-dose functional cure
Neutrophil elastase inhibitors — direct protease blockade independent of AAT level; research stage

Complications

  • Early-onset emphysema
  • COPD
  • Respiratory failure
  • Pulmonary hypertension
  • Cor pulmonale
  • Cirrhosis
  • Liver failure
  • Hepatocellular carcinoma
  • Panniculitis
  • Death

Prognosis

  • Prognosis varies widely.
  • The major factors affecting prognosis include:
    • Smoking
    • Severity of deficiency
    • Degree of lung damage
    • Presence of liver disease
  • Smokers develop lung disease earlier and more rapidly.
  • Early diagnosis and smoking avoidance can significantly improve outcomes.
  • Advanced lung or liver disease may require transplantation.

Key Points / Clinical Pearls

  • Alpha-1 Antitrypsin Deficiency is caused by mutations in the SERPINA1 gene.
  • It mainly affects the lungs and liver.
  • Lung disease results from unopposed neutrophil elastase activity.
  • Liver disease results from abnormal AAT accumulation in hepatocytes.
  • Consider it in young patients with early emphysema.
  • Lower-lung predominant emphysema is a classic pattern.
  • Smoking dramatically accelerates lung damage.
  • Low serum AAT is followed by genotyping or phenotyping for confirmation.