Alpha-1 Antitrypsin (A1AT)

Overview

Alpha-1 Antitrypsin (A1AT) is a serine protease inhibitor encoded by the SERPINA1 gene, as described on page 2 of the document. It is produced mainly in the liver and plays a critical protective role by inhibiting neutrophil elastase, a powerful enzyme that can damage lung tissue if left uncontrolled (page 3). When A1AT is deficient or dysfunctional, the lungs lose this protective barrier and become vulnerable to inflammation, irritants, and environmental exposures such as smoke and dust.

A1AT deficiency is a genetic disorder caused by mutations in SERPINA1, leading to inadequate production or abnormal folding of the protein. The condition can cause lung diseases such as emphysema and COPD, and liver conditions such as cirrhosis or hepatomegaly, detailed on page 5. The genetics section (page 4) highlights the codominant inheritance pattern and common deficient genotypes like PiZZ and PiSZ, which significantly impair A1AT function.

In clinical practice, A1AT levels and genetic or phenotypic testing (page 10) help diagnose deficiency, determine severity, and guide management.

Symptoms

Symptoms stem from A1AT deficiency’s effects on the lungs and liver, as summarized in the symptom table on page 9.

Lung-Related Symptoms

These arise from unchecked neutrophil elastase activity, damaging lung tissues:

1. Wheezing
2. Shortness of breath
3. Fatigue
4. Frequent colds or flu-like episodes
5. Chronic cough with phlegm

These symptoms closely resemble COPD and emphysema, conditions strongly associated with A1AT deficiency (page 3).

Liver-Related Symptoms

Impaired A1AT processing in the liver can result in:

1. Jaundice
2. Swelling in the legs or abdomen
3. Vomiting blood

Liver disease is especially common in children with severe A1AT deficiency, as noted on page 3.

Causes

The primary cause is a genetic mutation in the SERPINA1 gene, leading to insufficient A1AT levels or abnormal protein that accumulates in the liver instead of entering the bloodstream.

Key Biological Causes

(From pages 2, 3, 5, and 7)

1. SERPINA1 mutations: Defective alleles (especially Z and S variants) reduce effective A1AT production.
2. Autosomal codominant inheritance: A person must inherit two mutated alleles (one from each parent) to develop full deficiency.
3. Abnormal protein folding: Misfolded A1AT accumulates in liver cells, contributing to liver damage (page 6 diagram).
4. Uncontrolled neutrophil elastase: Without A1AT, this enzyme destroys lung tissue, leading to emphysema and reduced lung density.

Functional Consequences

1. Panlobular emphysema, airspace enlargement, and decreased lung tissue density (page 5).
2. Liver conditions such as cirrhosis or hepatomegaly due to retained misfolded protein in hepatocytes (page 5).

Risk Factors

Risk factors are directly tied to genetics, environmental exposures, and clinical scenarios where A1AT deficiency is more likely or more harmful.

1. Genetic Predisposition

1. Having two abnormal SERPINA1 alleles (e.g., PiZZ or PiSZ) significantly increases risk (page 4).
2. Carriers with one mutated allele still have increased lung disease risk (page 7).

2. Environmental Exposures

Although not the root cause, exposures like smoking, pollution, and dust worsen lung damage in people with deficiency (page 3).

3. Age Factor

People with A1AT deficiency often develop lung or liver disease before age 45 (page 7).

4. Associated Clinical Conditions

The indications table on page 12 identifies risk-associated conditions:

1. COPD/emphysema with unexplained obstruction
2. Chronic liver disease
3. Adult-onset asthma with fixed obstruction
4. Necrotizing panniculitis
5. Bronchiectasis of unclear cause

5. Family History

First-degree relatives of individuals with a deficiency are at increased risk and may require screening (page 12).

Prevention

While genetic mutations cannot be prevented, the document outlines ways to prevent diagnostic delays, disease progression, and testing errors.

1. Early Testing and Diagnosis

(From pages 10, 12, and 17)

1. Perform blood level testing, genotyping, or phenotyping when symptoms or family history suggest risk.
2. Combine clinical evaluation with lab testing to avoid false-low results and misinterpretation (page 17).

2. Proper Sample Collection

(Page 14)

1. Collect 3.0 mL of blood in a plain or EDTA tube.
2. Separate serum or plasma early to maintain accuracy.
3. Finger prick and cheek swab options are available.

3. No Special Preparation Needed

(Page 13)

Patients do not require dietary restrictions or medication adjustments before testing.

4. Avoid Environmental Lung Irritants

Though not a cure, minimizing exposure to smoke, pollution, and dust helps prevent rapid lung deterioration (page 3).

5. Family Screening

Testing siblings or relatives helps identify carriers and affected individuals early (page 12).