Idiopathic pulmonary fibrosis is a common type of interstitial lung disease that results in scarring of lung tissue. Fibrosis of lungs results in coughing and shortness of breath, two characteristic features of the disease.
Symptoms of idiopathic pulmonary fibrosis are nonspecific, with dyspnea and non-productive cough being the most common. Some nonspecific, systemic symptoms like weight loss, fever, and myalgia also may be present. Specific symptoms of the disease may develop gradually and may take one to two years to manifest. About 5% of the patients may remain asymptomatic, but can be diagnosed using a chest radiograph. Bibasilar inspiratory crackles are common among patients with this disease. About half of the patients may also show digital clubbing . Pulmonary hypertension is common among patients with idiopathic pulmonary fibrosis.
Many patients ignore shortness of breath, considering it as a part of ageing, but symptoms may worsen in time and necessitate medical attention. With disease progression, many patients face exacerbations and this may be followed by a short period of improvement. As symptoms become severe, oxygen levels reduce in different organs and increase pressure in lungs. This may lead to heart failure.
Many of the non-specific symptoms resembling that of respiratory and cardiac diseases along with bibasilar inspiratory crackle are suggestive of idiopathic pulmonary fibrosis. Chest radiography may be abnormal with reticular opacities, particularly in the lower lobe of the lungs. To get a more sensitive and specific image of the organ, high-resolution computed tomography (HRCT) is recommended. HRCT images give the characteristic, subpleural, reticular opacities that help in confirmation. Opacities refer to regions of tissue scarring and honey combing. Differential diagnosis of reticular opacities include heart failure, bronchiolitis–associated interstitial lung disease, and hypersensitivity pneumonitis. Thus the definitive diagnosis of this condition depends on subpleural reticular opacities and honey combing without any of the other features like cysts, extensive abnormalities, or micronodules .
Pulmonary function tests reveal ventilator defect and reduced diffusion of carbon dioxide . Results of this test is used along with clinical and radiographic findings in the diagnosis of idiopathic pulmonary fibrosis. Pulmonary function test may reveal reduced levels of total lung capacity. Biopsy of the affected tissue is the best way to distinguish idiopathic pulmonary fibrosis from other pulmonary diseases.
Histology tests show characteristic interstitial pneumonia with variegated tissue structure in lungs. Healthy tissue is alternated with interstitial inflammation and fibrosis. Small zones of heavy lung injury can be spotted in between collagen deposits. These areas or foci of fibroblasts help in definitive diagnosis of the condition. Presence of dilated bronchioles distributed between fibrosis, called the honey comb structure, is also characteristic of idiopathic pulmonary fibrosis. Diagnosis of idiopathic pulmonary fibrosis is based on the presence of usual interstitial pneumonia pattern in the lung tissue in the absence of any other known causes of interstitial lung disease.
A complete cure or an optimal therapy for the condition is not defined. Idiopathic pulmonary fibrosis has comorbid conditions like gastroesophageal reflux disease, obstructive sleep apnea, and coronary artery disease. Thus, optimal treatment of the disease should include the treatment of comorbid conditions. Most of the treatment modalities aim at improving the symptoms and preventing complications. Anti-inflammatory medications and immune modulators were used earlier, based on the theory that idiopathic pulmonary fibrosis is caused by inflammation of the lungs followed by fibrosis.
Controlling gastroesophageal reflux disease with appropriate medication is found to reduce fibrosis of lung tissue. Patients who are smokers are recommended to quit smoking. Oxygen therapy is suggested for patients with hypoxemia. Immunization against influenza virus and pneumococcus is important to prevent complications. For those with forced vital capacity between 50% and 80%, pirfenidone is recommended. Corticosteroids, alone or in combination with cyclophosphamide, are used in exacerbations. Pulmonary rehabilitation is also suggested for most of the patients. N-acetylcysteine is used in some countries. Lung transplantation is a recommended therapy and is found to be more beneficial than medications. Patients for this surgical method are chosen on a basis of a lung allocation score. The five-year survival rates after transplantation is reported to be 50-56% .
The rate of disease progression varies from person to person. In some people, medication may reduce the progression, while in others the condition may remain stable for long periods. Some patients may have exacerbations resulting in respiratory troubles. Lung transplantation is found to improve the condition in many patients. One of the studies report the mean life expectancy in patients with idiopathic pulmonary fibrosis to be around 3-5 years. Death rate is found to be related to aging. One of the most common cause of death due to idiopathic pulmonary fibrosis is an acute exacerbation of the condition. The mortality rate of the condition is found to be around 58-64 deaths in a million .
The actual etiology of the disease is not known. It was thought earlier that general inflammation of the lungs gradually leads to fibrosis. This theory lost consensus and was replaced by activation of fibroblasts as the prominent cause of fibrosis . Epithelial injury followed by activation of fibroblasts is thought to initiate a chain of events that result in alveolitis. Lung shows healthy tissue interspersed with interstitial tissue inflammation, fibrosis and a honeycomb structure. Studies report the link between idiopathic pulmonary fibrosis with various occupations that expose an individual to dust or fume, like industrial car cleaning, dairy, diamond polishing, gold extraction, and welding. Presence of silica, and metals like iron and nickel in the lungs is found to increase the risk of this condition . Smoking and certain medications like amiodarone, nitrofurantoin also may lead to interstitial lung disease. Pulmonary fibrosis may result as a complication of some infections including that of Mycoplasma pneumoniae, Influenza A2 virus, and Legionella pneumophilia.
Estimates of prevalence of this condition are limited. Prevalence from different part of the world ranges from 7 to 20 cases per 100,000 among the general population . It can occur in any age group, but the mean age of prevalence is reported to be around 66.9 years. Prevalence was higher among males than females in the ratio 20:13 in 100,000 people. The incidence rate among adults above the age of 60 years was reported to be 8.8 cases per 100,000 . Racial, geographical and ethnic influences on the incidence of this condition is still not known . Differences in diagnostic criteria, exposure to risk factors and labeling by physicians may affect the incidence and prevalence rate in different parts of the world. Mortality rate for this disease was found to be highest in United States. The rate seems to be increasing in some countries like United States, England and Australia. There are some who believe that idiopathic pulmonary fibrosis might run in families, but the majority view goes against this and there is no clear consensus on this issue.
An earlier hypothesis stating inflammation of lung tissue leads to fibrosis, was rejected later. A more recent theory puts forward inflammation of epithelial tissue followed by activation of fibroblasts as the main steps leading to pulmonary fibrosis. Homeostasis of epithelial tissue is changed by a number of endogenous and exogenous factors that trigger a chain of events resulting in fibrosis . The first step in the cascade is the damage in epithelial tissue of alveoli due to environmental triggers like pollution, viral infection, gastroesophageal reflux disease, and smoke. The epithelial tissue then tries to heal the affected tissue. In idiopathic pulmonary fibrosis, anomalous wound healing commences wherein the mesenchymal cells are activated resulting in the formation of a fibroblastic foci. Activated cells release cytokines and other growth factors which in turn trigger proliferation of fibroblasts. This is followed by fibrogenesis and secretion of extracellular matrix. Accumulated extracellular matrix in the tissue then causes contraction of tissue . Myofibroblasts of the wound healing tissue loses its apoptopic ability proliferating continuously. A study conducted on the lung tissue from idiopathic pulmonary fibrosis patients shows that deficiency of prostaglandin E2 results in increased cell death of epithelial cells and reduced apoptosis of fibroblasts cells, the two most common reasons for progressive fibrosis of tissue . Mutation in telomerase resulting in loss of epithelial cells in alveoli is a probable genetic explanation given for the occurrence .
As etiology of this condition is not known, prevention is not possible. Quitting smoking and avoiding exposure to environmental triggers are very important in reducing the risk of developing idiopathic pulmonary fibrosis. Those who are at a higher risk of developing this condition in any of the occupations, should wear breathing devices to limit exposure to chemicals.
Idiopathic pulmonary fibrosis is the most common type of fibrosing alveolitis with an unknown etiology. This progressive condition that results in scarring of lung tissue has a poor prognosis . It is mostly seen in older adults in the age group of 50 to 70 years and develops gradually over a period of six months. Signs and symptoms of the disease are not specific, and very often diagnosis may take more than a year or two . The actual cause of the condition is not yet known and there are no proven treatment modalities for the disease. Histology of the lungs shows signs of usual interstitial pneumonia. Inflammation and fibrosis of lung tissue are the most characteristic features of this disease. In many cases lung transplantation is the only known effective method to improve the condition.
Idiopathic pulmonary fibrosis is a debilitating condition characterized by scarring and damage of lungs. Scarring or fibrosis of lungs results in shortness of breath. It is a rare condition and is more common in older adults, particularly in those above 50 years of age. Prevalence is also more common among men when compared to women. The damage to lungs caused by the disease is irreversible, but many treatment modalities are available to improve symptoms of the disease.
The actual cause of the disease is not defined. Smoking, exposure to harmful chemicals, and certain infections are known to increase the risk of developing this condition. Progress of the disease varies from person to person. In some people the progress happens very fast, while in some it is slow. In some others the condition may remain the same without any significant changes. Most of the symptoms of the condition are nonspecific. Some of the common symptoms include dry cough, shortness of breath, weight loss, fever, and muscle pain.
A complete physical examination, particularly the sound of breathing pattern, is used to diagnose abnormalities in the structure and function of lungs. Imaging techniques like chest X-ray, CT scan and echocardiogram help in determining the location and extent of damage to lungs. Pulmonary function test, oximetry and exercise stress test are useful in monitoring lung function. Biopsy of the affected tissue is a confirmatory diagnostic test for idiopathic pulmonary fibrosis.
Complete cure for this condition is not yet available. Most of the treatment modalities used are useful in reducing the progress of the disease. Steroids, alone or in combination with immunosuppressant, represent the most common medication used for treating idiopathic pulmonary fibrosis. Oxygen therapy is used to reduce complications due to low oxygen levels. Lung transplantation is a suitable option for many people and is known to improve the condition in more than 50% of the patients. Pulmonary rehabilitation exercises are helpful in improving the functioning of lungs.