The term interstitial lung diseases refer to a group of conditions which ultimately results in the progressive destruction of alveolar tissue. Usually air enters the alveolar sack in the lung during inhalation. In the walls of the alveoli, there are small blood vessels. Normally oxygen is added from the air in the air sacs into the blood in the blood vessels which lines the wall of the air sacs during breathing. Carbon dioxide is removed from the blood during exhalation. In interstitial lung diseases, these thin walls of the alveoli are inflamed, scarred and thickened, so that exchange of carbon dioxide and oxygen does not happen. The scarring makes the wall less elestatic, making breathing difficult. This scarring and fibrosis is progressive and irreversible. Treatment may delay the progress, but damage is permanent.
Causes
1. Autoimmune disease such as rheumatoid arthritis and systemic lupus erythematosis.
2. Occupational and environmental causes such as exposure to toxins and pollutants, ammonia and chlorine gasses, moldy hay, bacterial and fungal overgrowth in humidifiers can all lead to ILD.
3. Infections- cytomegalovirus in HIV patients, fungal infections such as histoplasmosis, parasitic infections.
4. radiation treatment for lung cancer
5. drug chemotherapy medications such as psychotic medications and some antibiotics
6. Unknown cause- idiopathic pulmonary fibrosis.
Symptoms
1. difficulty in breathing
2. exercise intolerance
3. dry cough
4. Clubbing of nails.
5. right heart failure as disease progresses
Diagnosis
Diagnosis can be difficult and hard to distinguish from other diseases such as heart failure and chronic obstructive pulmonary disease or COPD. Detailed medical history can give a clue to the diagnosis. Examination of the chest may show crackling sounds. Chest x-ray can elimate other causes such as atelectasis and emphysema. High resolution CT may help the diagnosis. Pulmonary function tests shows restrictive pattern. Arterial blood gases shows decrease in oxygen. Broncoscopy and bronchoalveolar lavage may show the cause. Lung biopsy may be definitive in diagnosis.
Treatment
Corticosteroids are used to treat this condition. Benefits may be temporary and the side effects are considerable.
Azothioprine is used in combination with steroids. This also has major side effects such as decreased red blood cell production and increased risk of infection.
Cyclophosphomide is sometimes tried but has serious side effects.
Acetyl cysteine when combined with steroids and azothioprine, improves lung function in some patients.
Antifibrotics such as boseten and perfinidine, slows the progress of lung damage.
Oxygen therapy may help to improve the patients’ quality of life.
Lung transplant may be a final option.
Complication
This disease progresses gradually to respiratory failure. Drugs may delay progress of the disease but do no cure it. Only 50% of patients survive longer than 5 years. Ten percent of survivors develop lung cancer. |
