Fibrotic disease is caused by the formation of fibrosis. Pulmonary fibrosis is the development of excess fibrous connective tissue (fibrosis) in the lungs. It is also described as "scarring of the lung".
Pulmonary fibrosis may be a secondary effect of other diseases. Most of these are classified as interstitial lung diseases. Examples include autoimmune disorders, viral infections or other microscopic injuries to the lung.
However, pulmonary fibrosis can also appear without any known cause. In this case, it is termed "idiopathic". Most idiopathic cases are diagnosed as idiopathic pulmonary fibrosis. This is a diagnosis of exclusion of a characteristic set of histologic/pathologic features known as usual interstitial pneumonia (UIP).
In either case, there is a growing body of evidence which points to a genetic predisposition in a subset of patients. For example, a mutation in Surfactant protein C (SP-C) has been found to exist in some families with a history of pulmonary fibrosis.
Some diseases and conditions that may cause pulmonary fibrosis as a secondary effect include the following:
* Inhalation of environmental and occupational pollutants, such as in asbestosis, silicosis, and exposure to certain gases. Coal miners, ship workers and sand blasters among others are at higher risk. Hypersensitivity pneumonitis, most often resulting from inhaling dust contaminated with bacterial, fungal, or animal products.
* Cigarette smoking can increase the risk or make the illness worse.
* Some typical connective tissue diseases such as rheumatoid arthritis, SLE, and scleroderma.
* Other diseases that involve connective tissue, such as sarcoidosis and Wegener's granulomatosis.
* Infections, including bacterial, viral, and fungal.
* Certain medications, for example amiodarone, bleomycin, busulfan, methotrexate, and nitrofurantoin.
* Radiation therapy to the region of the chest.
As you can see, the possible causes of fibrotic lung disease are many and varied. The fibrosis is just a description of the findings on studies, but does not tell the physician about the cause in most cases. That usually has to be determined from the patients past medical history.