Interstitial lung diseases are a group of diseases, caused by inflammation and scarring of the alveoli (air sacs) and their supporting structures (the interstitium). This leads to the loss of the functional alveolar units and a reduction of the transfer of oxygen from air to blood.

There are dozens of different causes of ILD, and the classification systems are often confusing. In fact, many experts disagree on the best classification system for the interstitial lung diseases.

The interstitial lung diseases can be broken down into two large groups: those that have no known cause (idiopathic ILD) and those with an identifiable cause. One recent classification of idiopathic ILD includes the subclasses called: idiopathic pulmonary fibrosis/ usual interstitial pneumonitis (IPF/UIP), non-specific interstitial pneumonitis (NSIP), and acute interstitial pneumonitis (AIP). Sarcoidosis is a relatively common disorder that often causes interstitial lung disease.

Many occupational toxins, such as silica (sand) dust, asbestos fibers, coal dust, and cotton dust can cause ILD. Occasionally, hobbies such as keeping birds or bathing in hot tubs cause some forms of ILD.

Many connective tissue diseases (such as rheumatoid arthritis, scleroderma, and lupus) can cause interstitial lung disease. Some medications (examples include bleomycin, amiodarone, and methotrexate) may cause ILD.

The risk factors, genetic predispositions and incidence of ILD depend on the specific disease being considered. Sarcoidosis, for example, is relatively common in some ethnic groups (African Americans), whereas idiopathic pulmonary fibrosis is quite rare.

People who work in industries with heavy exposures to known causes of occupational lung disease (for example, coal miners, sand-blasters, ship workers) are usually screened routinely for lung disease.

Cigarette smoking increases the risk of developing ILD and can cause the disease to be more severe.

• shortness of breath at rest or on exertion
• decreased tolerance for activity
• dry cough

• cyanosis (blue discoloration of the lips, skin, or fingernails due to low blood oxygen levels)
• abnormal enlargement of the bases of the fingernails (clubbing)
• dry, crackling breath sounds by stethoscope examination of the chest (auscultation)
• nasal flaring
• rapid breathing

The following tests may be ordered:

• chest X-ray
• high-resolution CT scan of the chest
• pulmonary function tests
• measurement of the blood oxygen level at rest or during exertion
• blood tests to evaluate for connective tissue diseases
• bronchoscopy with transbronchial biopsy
• surgical lung biopsy

The treatment depends upon the underlying cause of the disease. Most often, anti-inflammatory drugs, such as corticosteroids or immunosuppressing drugs, are given. If there is no specific treatment for an underlying disorder, supportive therapy is indicated. Supplemental oxygen is prescribed for people with low blood oxygen levels. Pulmonary rehabilitation can help people combat the debilitation that accompanies advanced ILD.

Exposure to agents known to cause lung disease (certain dusts, gases, fumes, vapors, medications, and radiation) should be restricted.

Quitting cigarettes can slow the progression of existing ILD.

Lung transplantation may be indicated in some patients with advanced ILD.

The stress of the illness can often be helped by joining a support group where members share common experiences and problems. See lung disease - support group.

Chances for recovery or progression of the disease depend on the underlying cause.

• hypoxemia
• pulmonary hypertension
• right sided heart failure (cor pulmonale)
• respiratory failure

Call your health care provider if you have shortness of breath at rest that lasts for any duration.

Avoid exposure to agents known to cause lung disease.