In pulmonary fibrosis, the lung tissue is increasingly replaced by scar tissue, which gradually worsens lung function. Pulmonary fibrosis is therefore primarily noticeable through symptoms such as shortness of breath and an irritating cough. Fibrosis of the lungs can be caused by various diseases, infections or other harmful influences. Often, however, no cause can be identified – this is then referred to as idiopathic pulmonary fibrosis. The course, therapy and life expectancy depend on the form of pulmonary fibrosis and are therefore different for each individual patient.
What is pulmonary fibrosis?
Pulmonary fibrosis refers to a process in the lungs in which there is a pathological proliferation of scarred connective tissue in the intercellular spaces (interstitium). As a result, the functional tissue – the alveoli – is gradually displaced and lung function progressively deteriorates. The cause is chronic inflammatory processes in the lungs, which can be triggered by various factors.
Pulmonary fibrosis: symptoms include an irritable cough and shortness of breath
Incipient pulmonary fibrosis is initially noticeable by shortness of breath during exertion – later, shortness of breath usually occurs even at rest. In addition, patients often complain of a dry, irritating cough. If necessary – for example, if an infection is the cause – fever may occur. In the advanced stage, changes can usually also be seen on the hands: Due to the chronic lack of oxygen, there may be a bulging of the nails (clock glass nails) as well as a widening of the fingertips (drumstick fingers). Blue discoloration of the skin may also occur (cyanosis).
Classification of fibrosis according to cause
There are two main groups of pulmonary fibrosis: secondary and idiopathic. Secondary pulmonary fibrosis is said to occur when a cause for the fibrotic lung change can be identified. For example, the following diseases and factors can be considered as triggers for such secondary pulmonary fibrosis:
- Infections, for example, with viruses, the fungus Pneumocystis jirovecii or Legionella.
- Autoimmune diseases such as sarcoidosis
- Diseases of the connective tissue (collagenoses) such as scleroderma, systemic lupus erythematosus or Sjögren’s syndrome.
- Rheumatic diseases such as chronic polyarthritis or vascular inflammation (vasculitides).
- Lung diseases caused by inhaled dust – such as asbestos, quartz dust or metals (pneumoconiosis) or fine dust (exogenous allergic alveolitis).
- Inhaled pollutants such as gases, vapors or tobacco smoke.
- Certain drugs (for example, chemotherapeutic agents)
- Ionizing radiation, such as after radiation therapy.
- Diseases that cause chronic overhydration of the lungs (pulmonary edema), such as heart failure or kidney failure
- Certain forms of lung cancer (bronchioloalveolar carcinoma).
However, in about 50 percent of cases, no cause for pulmonary fibrosis can be found. It is then called “idiopathic interstitial pneumonia” (IIP), which means “pneumonia of the intercellular spaces of unknown cause”.
Risk factors for idiopathic pulmonary fibrosis.
Within the group of idiopathic pulmonary fibrosis, there are again several subtypes. The most common of these is known as idiopathic pulmonary fibrosis (IPF). Although by definition no cause can be found in idiopathic pulmonary fibrosis, studies indicate that there are some possible risk factors. Influences that may increase the risk for the disease include:
- Smoking
- Environmental pollutants such as metal dust, plant dust and livestock dust.
- Infections, such as with the Epstein-Barr virus or hepatitis C virus.
- Frequent heartburn (reflux disease)
- Diabetes mellitus
- Genetic factors
Diagnostics: finding possible causes
To make a diagnosis of secondary or idiopathic pulmonary fibrosis, the physician must first question the patient in detail regarding possible risk factors, previous illnesses, occupation and other influences. After a physical examination, a pulmonary function test is then usually performed. A blood test can estimate the severity of the lung damage via the oxygen content in the blood. In addition, certain values or markers in the blood can provide clues to possible causes of pulmonary fibrosis.
CT as a key diagnostic
Computed tomography (CT) plays an important role in diagnosis. As a rule, a so-called high-resolution CT is performed when pulmonary fibrosis is suspected (HR-CT) – it offers a higher resolution than conventional CT and can therefore show the changes in the lungs particularly well. A pattern typical of idiopathic pulmonary fibrosis is called “Usual Interstitial Pneumnonia (UIP)”. If this can be determined with certainty, the diagnosis of IPF is confirmed. In all other cases, a tissue sample of the lung (biopsy) may have to be taken. A so-called bronchoalveolar lavage, which is performed by means of lung endoscopy, may also be useful in some circumstances.
Idiopathic pulmonary fibrosis: medications not very promising
Treatment of secondary pulmonary fibrosis focuses on treating the cause or avoiding triggering factors. The treatment of idiopathic pulmonary fibrosis, on the other hand, is currently still the subject of research: numerous studies have tested the efficacy of various drugs, but no truly promising drug therapy has yet been found (as of October 2016). Under certain circumstances, treatment with drugs that suppress the immune system (immunosuppressants) – possibly in combination with cortisone-like agents (corticoids) – can lead to an improvement. According to recent studies, the active ingredient pirfenidone appears to be able to slow the progression of pulmonary fibrosis.
Pulmonary rehabilitation as a treatment option
In the absence of effective drug therapy options, nonpharmacologic treatment has a high priority in idiopathic pulmonary fibrosis. Special rehabilitation programs (known as pulmonary rehabilitation) are available for this purpose, including education, psychological support, and nutritional counseling, as well as moderate strength and endurance training.
Oxygen therapy can relieve symptoms
As lung function progressively deteriorates, the administration of oxygen can relieve symptoms and increase exercise capacity. Such oxygen therapy is possible at home and on the road using nasal cannulae and a portable oxygen cylinder. In addition, all patients with pulmonary fibrosis should stop smoking and receive influenza and pneumococcal vaccinations to prevent infections.
Lung transplantation: last option in end-stage disease
There is no cure for pulmonary fibrosis because the scarring of the lungs cannot be reversed. Therefore, the goal of treatment is to slow the progression of the disease and improve quality of life. In end-stage idiopathic pulmonary fibrosis, lung transplantation may therefore be considered. However, many patients are not suitable for transplantation because of concomitant diseases or excessive age.
Life expectancy: how long do patients with pulmonary fibrosis live?
Idiopathic pulmonary fibrosis is usually progressive, whereas the secondary form can be arrested if the cause is successfully treated. The course and prognosis of the disease are therefore different for each individual patient, and a general statement regarding life expectancy is not possible. However, the average survival time from diagnosis of pulmonary fibrosis is reported to be two to five years.
Pulmonary fibrosis and COPD
To be distinguished from pulmonary fibrosis are the so-called obstructive lung diseases, in which lung function is reduced not by scarring but by narrowing or obstruction of the airways – for example, by mucus. The best-known form is chronic obstructive pulmonary disease (COPD). The hereditary disease cystic fibrosis (which is also misleadingly called cystic fibrosis) is also an obstructive disease because the airways are blocked by viscous mucus. Pulmonary fibrosis, on the other hand, is called a restrictive lung disease because the scarring prevents the lungs from expanding properly and causes them to shrink, so to speak. However, it is not uncommon for COPD patients to also have pulmonary fibrosis – possibly due to the common risk factor of tobacco smoke.
