Alveolitis (Extrinsic Allergic)

Definition

Definition of Alveolitis (Extrinsic Allergic)
Extrinsic allergic alveolitis (EAA) refers to a group of lung diseases that can develop after exposure to certain substances. The name describes the origin and the nature of these diseases:

• 'extrinsic' - caused by something originating outside the body
• 'allergic' - an abnormally increased (hypersensitive) body reaction to a common substance
• 'alveolitis' - inflammation in the small air sacs of the lungs (alveoli)

Symptoms

Symptoms of Alveolitis (Extrinsic Allergic)
Symptoms can include: fever, cough, worsening breathlessness and weight loss.

Causes

Causes of Alveolitis (Extrinsic Allergic)
Extrinsic allergic alveolitis does not develop on the first day of exposure to animal and vegetable dusts. Repeated and prolonged exposure is necessary. Even then, only some workers develop allergic reactions to the dusts. Ten to forty percent (10 - 40%) of exposed people do not show any symptoms of extrinsic allergic alveolitis.

The allergy is triggered by complicated reactions of the body's natural defense system that normally protects the lungs from foreign substances. In some individuals, the chemical reactions of the defense system that would ordinarily protect the lungs actually cause the inflammation and lung damage. The body's changing response to the presence of dust in the lungs is called sensitization.

Diagnosis

Diagnosis of Alveolitis (Extrinsic Allergic)
The diagnosis of the disease is based on a history of symptoms after exposure to the allergen and a range of clinical tests which usually includes: X-rays or CT scans, lung function and blood tests.

Treatment

Treatment of Alveolitis (Extrinsic Allergic)

1. In acute severe cases with significant respiratory distress and/or the presence of cyanosis, consider immediate referral to hospital for further assessment.
2. Supplemental oxygen should be given to treat hypoxaemia.
3. In less severe acute cases, or in the chronic form, avoidance of exposure to the allergen, along with investigations to confirm or refute the diagnosis should be carried out, usually in conjunction with a respiratory specialist.
4. Once the diagnosis is made it is important to avoid allergen exposure. This may require a change of job. Before such a drastic step, consultation with a respiratory consultant or specialist in occupational medicine may be prudent.
5. In the acute form, simply avoiding further exposure will usually result in recovery without medication.
6. Corticosteroids may be indicated for the treatment of severe acute and subacute forms and for chronic forms that are severe or progressive. However, steroids don't seem to alter the long-term outcome.6 Exposure to the offending antigen still needs to be avoided as well.
7. In advanced chronic disease, pulmonary fibrosis can still progress and death can occur despite aggressive corticosteroid therapy.
8. Treatment in chronic or residual disease is supportive.

Prognosis

Prognosis of Alveolitis (Extrinsic Allergic)

1. Early recognition and control of exposure is key to outcome.
2. In acute and subacute forms, most patients recover lung function completely when exposure to the antigen stops. However, this may take several years for subacute forms.
3. Bird fancier's lung has a worse prognosis than farmer's lung.
4. The chronic form may be progressive and irreversible and result in debilitating fibrotic lung disease with high mortality rates.

Prevention

Prevention of Alveolitis (Extrinsic Allergic)
The means for reducing dust exposure (dust control) include engineering control and personal protective equipment. Education is also important, and educational programs should emphasize the significance of animal and vegetable dust in causing diseases. Managers and workers should learn about methods of storing materials to prevent mould formation and to reduce dust.