Idiopathic pulmonary fibrosis

What is idiopathic pulmonary fibrosis?

Idiopathic pulmonary fibrosis involves scarring or thickening of tissues deep in the lung without a known cause. It is a disease of the lower respiratory tract that damages the air sacs (alveoli) and leads to reduced transfer of oxygen to the blood. It causes widespread scarring of the lung. The condition is believed to result from an inflammatory response to an unknown agent (idiopathic means no cause can be found). The disease occurs most often in people between 50 and 70 years.

Even though the cause of IPF is not established, the following are considered to be risk factors for the disease:

• Working around dusts - particularly dust from asbestos, silica, wood or metal--as well as gases or other fumes.
  
• Exposure to radiation or chemotherapy
  
• Presence of connective tissue diseases, such as arthritis, lupus or systemic sclerosis
  
• History of smoking

What are the symptoms?

• Shortness of breath on exertion that lasts for months or years and eventually is present at rest
  
• Decreased tolerance for activity
  
• Cough
  
• Chest pain

How is it diagnosed?

In addition to a physical examination, a careful history is required in order to exlude other similar diseases. Patients with idiopathic pulmonary fibrosis tend to have a dry, velcro-like breath sounds called crackles. Patients with an advanced disease may have cyanosis (blueness around the mouth or in the fingernails due to low oxygen). Examination of the fingers and toes may reveal clubbing (abnormal enlargement of the tips). Tests that help diagnose idiopathic pulmonary fibrosis include the following:

• Chest X-ray
  
• High-resolution CT scan of the chest
  
• Lung function tests
  
• Bronchoscopy with transbronchial lung biopsy
  
• Surgical lung biopsy
  
• Measurement of blood oxygen level at rest or during exertion
  
• Tests for connective tissue diseases such as rheumatoid arthritis and lupus.

What is the treatment?

No known cure exists for idiopathic pulmonary fibrosis. Treatment is generally limited to an attempt to reduce symptoms of cough, wheezing and breathlessness. Medications such as corticosteroids and cytotoxic drugs may be given to suppress inflammation, but these treatments are usually unsuccessful. Oxygen is given to patients who have low blood oxygen levels. Lung transplantation may be indicated for some patients with advanced pulmonary fibrosis.

What is the prognosis?

Some patients may improve on treatment with corticosteroids or cytotoxic drugs, but most patients suffer from progressive disease despite treatment. Pulmonary hypertension (high blood pressures in the vessels of the lungs) and respiratory failure is the eventual outcome. Average survival time is 5-6 years, but this varies greatly between patients.

What are the complications?

• respiratory failure
  
• chronic hypoxemia (low blood oxygen level)
  
• pulmonary hypertension
  
• cor pulmonale (failure of the right side of the heart)
  
• polycythemia (abnormally high levels of red blood cells)

How can it be prevented?

Avoiding smoking may help prevent this condition. But since the cause is uncertain, more specific prevention is not known.