What is lung disease?
The term lung disease is a broad term that encompasses various pathologies that involve the lungs and related structures. Other organs and systems may also be involved, but the lung disease is often the primary disorder. At times the problem may lie in the airways or blood vessels of the lung (respiratory disease) but since the exchange of gases in the lung air sacs (alveoli) are affected, it is all considered within the ambit of lung disease.
Broadly lung disease can be categorized according to the disease process and mechanism by which it affects normal lung functioning. This often overlaps and includes :
- obstructive diseases that hamper air flow
- inflammatory diseases that affect lung elasticity and gas exchange in the alveoli
- infections which result in inflammation but are often considered separately
- fibrosis/scarring with loss of lung elasticity that often follows long term inflammation
- tumors which may block air flow and/or destroy lung tissue.
While conditions that affect the blood vessels may also affect lung functioning, it is often considered under cardiovascular diseases.
Lung disease can be acute, subacute or chronic although the term ‘lung disease’ is more commonly used to refer to subacute and chronic pathologies. Irrespective of the cause or type of lung disease, the respiratory function is almost always impaired to varying degrees.
Types of Lung Disease
There are many different types of lung disease but the most common include :
- Asthma (obstructive)
- Pneumonia (inflammatory/infectious)
- Acute bronchitis (inflammatory/infectious)
- Chronic bronchitis (inflammatory/fibrosis)
- Emphysema (inflammatory/fibrosis)
- Lung cancer (tumor)
Atelectasis and pulmonary edema are also considered under lung disease but usually stem from some other underlying pathology. Pneumoconiosis which is a a lung disease associated with the inhalation of certain dusts is not common except in occupations like mining, construction and working with materials like textiles.
Symptoms of Lung Disease
The signs and symptoms of different types of lung diseases may vary. Common signs and symptoms include :
- Persistent cough with sputum and/or hemoptysis (coughing up blood)
- Difficulty breathing (dyspnea)
- Abnormal breathing sounds
- Pallor (paleness of the skin) or cyanosis (bluish discoloration of the lips and skin)
- Fluid in the lungs (pulmonary edema)
Concomitant symptoms may include :
- Chest pain
- Changes in voice
Disturbance of lung function and the persisting disease can lead to :
- Consolidation of the lung
- Chest wall deformity
Smoker’s Lung Diseases Types
The two main respiratory diseases associated with prolonged and heavy cigarette smoking is chronic bronchitis and emphysema. These two diseases are grouped under the term chronic obstructive pulmonary disease because there is narrowing of the airways and impairment of air flow which is often irreversible. The pathogenesis of both diseases is explained further under :
Cigarette smoking can be a contributing factor to a number of other respiratory diseases, however, this is often associated with various other factors. Similarly, non-smokers may also develop chronic bronchitis or emphysema but this is rare and further investigation often reveals long term exposure to secondary smoke (passive smoking) or inhalation of mineral dusts like silica (silicosis).
Two less commonly discussed respiratory diseases associated with cigarette smoking are grouped under the term smoking- related restrictive pulmonary disease / interstitial pulmonary disease. These diseases include :
- desquamative interstitial pneumonia (DIP)
- respiratory bronchiolitis-associated interstitial lung disease.
Both diseases are characterized by an accumulation of dark-brown pigmented macrophages (smoker’s macrophages) in the air sacs of the lungs and respiratory bronchioles.
What is desquamative interstitial pneumonia?
Desquamative interstitial pneumonia is chronic lung inflammation where large amounts of macrophages infiltrate the air spaces of the lung. Other inflammatory cells like plasma cells, lymphocytes and eosinophils may also be seen in large quantities and the inflammatory infiltrate contributes to thickening of the alveolar septa.
What is respiratory bronchiolitis-associated interstitial lung disease?
Respiratory bronchiolitis-associated interstitial lung disease is inflammation of the small airways with accumulation of macrophages within the respiratory bronchioles. The airways may also be contain inflammatory infiltrate with an accumulation of lymphocytes and histiocytes.
When do these smoker’s lung diseases start?
There is no definitive time period for when these different type of smoker’s lung diseases will develop or become symptomatic. In most cases :
- chronic bronchitis is seen in the 40s to 50s
- emphysema is seen in the 50s to 70s
- desquamative interstitial pneumonia (DIP) is seen in the 40s to 50s but can occur as early as the 30s
- respiratory bronchiolitis-associated interstitial disease is seen in the 40s to 50s
The symptoms of most of these diseases are seen in smokers consuming at least 20 cigarettes for a period of 20 years or more (20 pack-years of smoking).
Smoker’s Lung Disease Symptoms
The predominant symptom in all types of smoking-related lung disease is difficulty breathing (dyspnea). This may be described as shortness of breath, breathlessness or breathing problems. The onset is usually gradual and progressive although it may not progress further or even improves with the cessation of smoking. It is an early feature of emphysema. Initially the dyspnea is apparent only upon exertion (exertional dyspnea) but eventually progresses to the point where it is constant even at rest.
Cough in smoker’s lung disease is another common feature and is most prominent in chronic bronchitis. Here a productive cough is seen in the early stages of the diseases. A dry cough may be seen in the other types of smoking-related respiratory disease and is a late feature of conditions like emphysema. Read more on chronic bronchitis vs emphysema symptoms.
Other symptoms may be more prominent or seen only with certain diseases :
- Clubbing – emphysema and DIP
- Cyanosis – chronic bronchitis and late stage emphysema
- Peripheral edema – swelling of the legs associated with right-sided heart failure in COPD