Idiopathic pulmonary fibrosis is an interstitial restrictive lung disease without a known cause.
Although the trigger for the disease is unknown, there are three known risk factors:
1. Age > 50 years
2. Male Gender
3. Tobacco Use
One of the features of restrictive lung diseases and, therefore, idiopathic pulmonary fibrosis is dyspnea that increases with exercise and cough.
As the disease progresses and dyspnea increases, the patient begins to feel fatigued.
On auscultation, patients with IPF may have crackles.
A clinical feature in various pulmonary diseases, such as idiopathic pulmonary fibrosis, is digital clubbing.
Another feature that can be found in the CT of patients with idiopathic pulmonary fibrosis is traction bronchiectasis, which appears as the lung displays more fibrosis. Those zones pull on normal lung areas.
Diagnosis of idiopathic pulmonary fibrosis is done with various studies, such as a CT, after other causes of pulmonary fibrosis have been ruled out.
A distinctive, but not exclusive, finding in CT of patients with idiopathic pulmonary fibrosis are basal and subpleural heterogenous infiltrates in a honeycomb pattern. Similarly, in CXR, patients display reticular or reticulonodular infiltrates in the bases (honeycomb lung).
In spirometry, the pattern seen is restrictive, with decreased total lung capacity, forced vital capacity, and forced expiratory volume in the first second. Since all volumes decrease, it is important to remember that the FEV1/CVF ratio is usually normal, which differentiates this pattern from obstructive lung disease.
Another feature is a decrease in diffusing capacity for carbon monoxide.
As fibrosis progresses, there is less functional lung tissue, and capillary resistance increases. This is further promoted by hypoxia, which leads to vasoconstriction in pulmonary capillaries. All of this gives rise to pulmonary hypertension and, eventually, respiratory failure.
Pulmonary hypertension and fibrosis lead to an increase in the force that the right ventricle has to exert to pump lungs towards the lungs. This increase causes the right heart to adapt and dilate, but as the disease progresses, right heart failure ensues. This failure, in turn, can lead to arrhythmias such as atrial fibrillation and atrial flutter, which can further worsen right heart function.
Idiopathic pulmonary fibrosis is a progressive disease that eventually causes respiratory failure and death. The only known treatment today is a lung transplant. As patients deteriorate, supplemental oxygen is used to alleviate symptoms.
Antifibrotic medications, like Pirfenidone and Nintedanib, are used to help slow down disease progression.
Ultimately, patients with idiopathic pulmonary fibrosis end up in respiratory failure, which makes lung transplant the only definitive therapeutic option.
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