Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF), formerly known as cryptogenic fibrosing alveolitis, is a rare, progressive illness of the respiratory system, characterized by the thickening and stiffening of lung tissue, that surrounds the air sacs, and is associated with the formation of scar tissue. It is a type of chronic pulmonary fibrosis characterized by a progressive and irreversible decline in lung function. Symptoms typically include gradual onset of shortness of breath and a dry cough. Other changes may include feeling tired, and clubbing (abnormally large and dome shaped finger and toenails). Complications may include pulmonary hypertension, heart failure, pneumonia or pulmonary embolism. The cause is unknown, hence the term idiopathic. Risk factors include cigarette smoking, gastroesophageal reflux disease, certain viral infections, and genetic predisposition. The underlying mechanism involves scarring of the lungs. Diagnosis requires ruling out other potential causes. It may be supported by a high resolution CT scan or lung biopsy which show usual interstitial pneumonia. It is a type of interstitial lung disease. People often benefit from pulmonary rehabilitation and supplemental oxygen. Anti-fibrotic medications like pirfenidone or nintedanib may slow the progression of the disease. Lung transplantation may also be an option. About 5 million people are affected globally. The disease newly occurs in about 12 per 100,000 people per year. Those in their 60s and 70s are most commonly affected. Males are affected more often than females. Average life expectancy following diagnosis is about four years. Updated international guidelines were published in 2022, which resulted in some simplification in diagnosis and the removal of antacids as a possible adjunct therapy.

Signs and symptoms

In many people, symptoms are present for a considerable time before diagnosis. The most common clinical features of IPF include the following:

Age over 50 years Dry, non-productive cough on exertion Progressive exertional dyspnea (shortness of breath with exercise) Dry, inspiratory bilateral basal crackles on auscultation (a crackling or popping sound in the lungs during inhalation). Clubbing of the digits, a disfigurement of the finger tips or toes (see image) Abnormal pulmonary function test results, with evidence of restriction and impaired gas exchange. Some of these features are due to chronic hypoxemia (oxygen deficiency in the blood), and are not specific for IPF, they can occur in other pulmonary disorders. IPF should be considered in all patients with unexplained chronic exertional dyspnea who present with cough, inspiratory bilateral basal crackles, or finger clubbing. Assessment of crackles on lung auscultation is a practical way to improve the earlier diagnosis of IPF. Fine crackles, also known as "velcro" crackles are easily recognized by clinicians and are characteristic of IPF. If bilateral fine crackles are present throughout the inspiratory time and are persisting after several deep breaths, and if remaining present on several occasions several weeks apart in a subject aged ≥60 years, this should raise the suspicion of IPF and lead to consideration of an HRCT scan of the chest which is more sensitive than a chest X-ray. As crackles are not specific for IPF, they must prompt a thorough diagnostic process.

Causes The cause of IPF is unknown but certain environmental factors and exposures have been shown to increase the risk of getting IPF. Cigarette smoking is the best recognized and most accepted risk factor for IPF, and increases the risk of IPF by about twofold. Other environmental and occupation exposures such as exposure to metal dust, wood dust, coal dust, silica, stone dust, biologic dusts coming from hay dust or mold spores or other agricultural products, and occupations related to farming/livestock have also been shown to increase the risk for IPF. There is some evidence that viral infections may be associated with idiopathic pulmonary fibrosis and other fibrotic lung diseases.

Pathogenesis

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