What is brown lung disease?
Brown lung disease, or byssinosis, is a reactive airway disease that leads to airway obstruction as a result of exposure to cotton dust (brack), flax and hemp. It is a type of occupational lung disease that is more commonly seen in cotton workers, those working in flax mills and textile workers.
In the acute stages it may cause recurrent episodes of bronchiolitis (bronchioles ~ small airways) with no ongoing signs and symptoms if the person discontinues working in the environment. At this stage it is known as acute byssinosis. Like other occupational lung diseases, the permanent damage is seen 20 to 30 years after exposure where it is known as chronic byssinosis.
Causes of Byssinosis
Although byssinosis is more frequently seen in textile/fabric workers and is known to be associated with cotton, flax or hemp, the actual cause is not clearly understood. It is believed that byssinosis may be a result of exposure to endotoxins from bacteria in the cotton. It is sometimes mistaken for occupational asthma. Byssinosis does not affect every textile worker and is more frequently seen in those who are cigarette smokers.
Swelling of the bronchioles due to inflammation (bronchiolitis) causes narrowing of the airways. This limits the flow of air through the respiratory passages and lung function diminishes. Despite the term brown lung disease, the lungs are not brown in color. Over the duration of the disease, the person is susceptible to repeated respiratory tract infections. Prolonged inflammation leads to scarring that permanently affects lung function.
Signs and Symptoms of Brown Lung Disease
Initially, the acute stage of brown lung diseases closely resembles asthma with pronounced breathlessness, chest tightness and wheezing. The condition is worse at the beginning of the week or upon acute exposure after a period away from the work environment. Hence the other common name for byssinosis – Monday fever. At this point the lung function decreases significantly due to airway obstruction. As the week progresses, the severity of the symptoms and impairment of lung function reduces (across-shift variation). This ‘improvement’ by the end of the week can often be misleading.
In the chronic setting, there is no easing of symptoms by the end of the week. Chronic byssinosis is sometimes mistaken for emphysema. However, cotton dust does not cause emphysema but this lung disease may be present as a result of long term cigarette smoking. Breathlessness, chest tightness, crackles and severely reduced lung function is irreversible in the chronic stage and can lead to respiratory failure. This is often accelerated by continued cigarette smoking despite the patient having stopped working in the textile industry.
Diagnosis of Byssinosis
A thorough medical history is one of the most important components of the diagnosis. Byssinosis should be suspected in textile workers, those with asthma-like symptoms that start on the first day of the work week and settle by the end of the week and especially if these workers are cigarette smokers. A chest x-ray and pulmonary function test will be necessary to confirm the diagnosis.
Despite the frequency of byssinosis in the textile industry, it should not detract from the possibility of other lung diseases. Chronic bronchitis and emphysema, despite the slight variation in symptoms, needs to be ruled out as well as asthma, as these lung diseases are more common. Due to medico-legal implications, it is important to correlate the symptoms and changes in lung function with the exposure to the work environment by careful case taking and spirometry. Chronic byssinosis may only be seen some 20 to 30 years after exposure.
Treatment of Byssinosis
In the acute setting, patients are encouraged to consider alternative occupations or at least reduce the exposure in the work environment.Workers who are cigarette smokers need to be advised on the compounding effect of smoking and should be encouraged to stop smoking.
In the acute stages, treatment may include :
- Brochodilators will offer symptomatic relief for breathlessness and wheezing.
- Corticosteroids are only considered in severe cases and are best avoided for as long as possible.
Chronic byssinosis is irreversible due to scarring of the lung tissue. Supportive measures may include :
- Nebulizer use
- Home oxygen therapy
Physical activity and breathing exercises may help in the management.