What Is Idiopathic Lung Fibrosis?

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrotic interstitial lung disease. The disease is localized in the lungs and is common in the elderly. Its lung histology and / or chest high-resolution CT (HRCT) is characterized by common interstitial pneumonia (UIP) with unclear etiology. According to the course of the disease, it can be divided into acute, subacute and chronic. The disease is mostly sporadic. According to statistics, the overall prevalence of the population is about (2-29) per 100,000, and it is gradually increasing, and it is estimated to be 11% per year Increase in proportion. There are approximately 100,000 patients with idiopathic pulmonary fibrosis in the United States, approximately 110,000 in the European Union, and 35,000 new IPF patients in the European Union each year. The overall prevalence of IPF in Japan is (2.23 to 10) per 100,000 per year, and the actual value is much higher than this number. As a country with severe aging, the number of patients with IPF is increasing year by year, and the conservative estimate is at least about 500,000. As a chronic interstitial lung disease, the onset of IPF is insidious, and the disease gradually worsens, which can also be manifested as acute exacerbation. The average survival time after diagnosis of IPF is only 2.8 years, and the mortality rate is higher than that of most tumors. IPF is called a "tumor-like disease".

Basic Information

English name: idiopathic pulmonary fibrosis
Visiting department: Respiratory

Multiple groups: 50 70 years old male
Common symptoms: Difficulty breathing, cough, expectoration, weight loss, fatigue, loss of appetite, joint pain, etc.

Causes of Idiopathic Pulmonary Fibrosis

The etiology of IPF is unknown and the pathogenesis is not fully elucidated, but there is sufficient evidence to suggest that it is related to immune inflammation damage. The immune inflammatory response characteristics displayed by different specimens are not the same. The peripheral blood reflects that the immune abnormality is more prominent, while the bronchoalveolar lavage fluid shows the inflammatory response mainly, and the abnormality of local lung tissue is different. This difference needs to be taken into account when evaluating various research materials. At present, alveolar epithelial cell damage and abnormal repair are the main mechanisms leading to pulmonary fibrosis. After the injury, the normal re-epithelialization process cannot be completed during the repair process, resulting in alveolar-capillary damage. This process induces cytokine production. Cytokine receptors are expressed on the surface of fibroblasts, which aggregate to the site of injury and proliferate under the action of cytokines.

Clinical manifestations of idiopathic pulmonary fibrosis

About 15% of IPF cases are acute. Progressive dyspnea is found due to upper respiratory tract infections. More than 6 months die of respiratory failure. Most IPFs are chronic (there may be intermediate subacute types), although the average chronic survival time is only 3.2 years. The chronic type does not appear to have evolved from the acute type, and the exact relationship is unknown.

Main symptoms

(1) Dyspnea Labor dyspnea and progressive aggravation, shallow breathing speed may have nasal fan movements and auxiliary muscles involved in breathing, but most of them do not sit breath.

(2) No cough in the early stage of cough and sputum , followed by dry cough or a small amount of mucus sputum, which is prone to secondary infection. Mucopurulent sputum or purulent sputum appears, with occasional blood sputum.

(3) Systemic symptoms may include weight loss, fatigue, loss of appetite, joint pain, etc., which are generally rare, and the acute type may have fever.

2. Common signs

(1) Dyspnea and cyanosis.

(2) Dilatation of thorax and reduction of diaphragm activity.

(3) Velcro rales in the lower and middle lungs are characteristic.

(4) clubbing fingers and toes.

(5) Corresponding signs of end-stage respiratory failure and right heart failure.

Classification of Idiopathic Pulmonary Fibrosis

According to the international multidisciplinary classification of idiopathic interstitial pneumonia (IIPs) published by the American Thoracic Society / European Respiratory Society in 2013, IIPs are divided into major IIPs, rare IIPs, and unclassifiable IIPs. There are six main types of IIPs, including IPF, idiopathic non-specific interstitial pneumonia (iNSIP), respiratory bronchiolitis with interstitial lung disease (RB-ILD), and desquamative interstitial pneumonia (DIP ), Cryptogenic organizing pneumonia (COP), acute interstitial pneumonia (AIP). There are two types of rare IIPs, including idiopathic lymphocytic interstitial pneumonia (iLIP) and idiopathic pleural pulmonary parenchyma elastic fibrosis (iPPFE). IPF is the most common type of major idiopathic interstitial pneumonia.

Idiopathic pulmonary fibrosis

Imaging examination

(1) Conventional X-ray chest radiography technology should pay attention to the appropriate penetration conditions, the application of moderately sensitized screens, focus should be small. Early X-rays of alveolar inflammation cannot show abnormalities; as the lesion progresses, the X-rays show a cloud-like, faintly visible small dot-like diffuse shadow, like ground glass. Further progress shows that fibrosis becomes more and more obvious, from slender reticulation to coarse reticulation, or reticulate nodules. In the later stages, there are cystic changes of varying sizes, namely honeycomb lungs. Lung volume decreases, diaphragmatic muscles rise, and interlobular fissures shift.

(2) The contrast resolution of CT is better than that of X-rays. The application of high-resolution CT (HRCT) can further improve the spatial resolution, which is extremely helpful for the diagnosis of IPF, especially the early identification of alveolitis and fibrosis and the discovery of cellular lungs.

(3) Nuclide IPF often has increased alveolar capillary membrane permeability. Radionuclide inhalation of ^99m Tc-DTPA aerosol to measure pulmonary epithelial permeability (LEP) shows a shortened T1 / 2, which is helpful for early detection and diagnosis of interstitial lung disease and is not specific for IPF.

2. Pulmonary function test

Typical changes in lung function in IPF include restricted ventilation impairment, reduced lung volume, decreased lung compliance, and reduced diffusion. In severe cases, PaO ₂ decreases and PA-aO ₂ widens. Pulmonary function tests and imaging techniques are helpful for early diagnosis, especially exercise tests that have reduced diffusion and hypoxemia before the appearance of imaging abnormalities. Pulmonary function tests can be used for dynamic observations, which are very helpful for evaluating the condition, and may also be useful for assessing the efficacy. Similarly, IPF's pulmonary dysfunction is not specific and has no differential diagnostic value.

3.Bronchoalveolar lavage

The total number of cells in bronchoalveolar lavage fluid increased, and the increase in the proportion of neutrophils is a typical change of IPF, which is helpful for diagnosis. It is still mainly used for research.

4. Lung biopsy

The early and mid-term histological changes of IPF have certain characteristics, and the etiology of interstitial lung disease includes many people with clear etiology. Therefore, lung biopsy is very meaningful for the diagnosis and activity evaluation of this disease. The fiberoptic bronchoscope is the first choice for TBLB, but the specimen is small and the diagnosis is difficult. If necessary, thoracoscopy or open lung biopsy should be performed.

Idiopathic pulmonary fibrosis diagnosis

1. Clinical manifestations: the age of onset is mostly middle-aged and above, with more men than women. Onset of hidden attacks, mainly manifested by dry cough, progressive dyspnea, obvious after activity. Most patients can hear end-inspiratory popping sounds or twisting sounds in both lower lungs, and more than half can see clubbed fingers (toes). End-stage cyanosis, pulmonary hypertension, pulmonary heart disease, and right heart dysfunction.

2. Chest HRCT: Chest HRCT is a necessary diagnostic tool for the diagnosis of IPF. The diagnostic value of chest radiographs for patients with suspected IPF is significantly lower than HRCT, and should not be used as a basis for the diagnosis of IPF. The chest HRCT of IPF is mainly characterized by grid shadow and honeycomb lung, which is often accompanied by traction bronchiectasis [2], of which honeycomb lung is an important basis for the diagnosis of positive UIP. Ground glass shadows are rare and usually have a smaller range than grid shadows. The typical UIP distribution characteristics of chest HRCT are double lower lung and outer band distribution.

Complicated pleural abnormalities, such as pleural plaques, calcifications, and significant pleural effusions, are more likely to cause UIP-type lesions caused by other diseases. Micronodules, gas traps, non-honeycomb lung cystic shadows, extensive ground glass shadows, consolidation, or distribution along the bronchial blood vessels suggest other diagnoses.

3. Histopathological examination: The characteristic histopathological change of IPF is common interstitial pneumonia, the main lesion of which is fibrosis, and the extent and distribution of the lesions are inconsistent. Observed under a low-power microscope, it can also be seen that the scar fibrosis area is accompanied by There are honeycomb lung changes, and the lesions are milder and even the area of normal lung tissue [2]. These histopathological changes are usually manifested in the subpleural and paraseptal lung parenchyma. Inflammation is usually mild, with a small amount of infiltration of lymphocytes and plasma cells, with proliferation of type 2 alveolar epithelial cells and bronchiolar epithelial cells. The fibrotic area is mainly composed of dense collagen fibers, and scattered fibroblastic foci are visible. The honeycomb lung area consists of a cystic fibrotic air cavity, usually lined with bronchiolar epithelial cells, which are filled with mucus and inflammatory cells. In pulmonary fibrosis and honeycomb lung lesions, smooth muscle hyperplasia can be seen in the lung interstitial.

Diagnostic criteria

(1) Exclude interstitial lung diseases caused by known causes, such as occupational exposure, indoor and outdoor environmental exposure, connective tissue disease, and drug-induced lung damage.

(2) In patients who have not undergone a surgical lung biopsy, the HRCT of the chest is positive UIP.

(3) For patients undergoing surgical lung biopsy, a combination of HRCT and surgical lung biopsy meets a specific type.

Idiopathic pulmonary fibrosis treatment

(1) Drug treatment

(1) Pirfenidone:

Pirfenidone is two of the "Recommended Guidelines for the Clinical Treatment of Idiopathic Pulmonary Fibrosis" jointly issued by the American Thoracic Society / European Respiratory Association / Japanese Chest Association / Latin American Chest Association in 2015. One of the drugs, after 52 weeks of continuous treatment with pirfenidone, IPF patients can slow down the decline of lung function indicators such as FVC and DLCO, prolong the progression-free survival (PFS) of patients, and reduce the risk of death.

(2) Nidanib: Nidanib is in the "Recommended Guidelines for Clinical Treatment of Idiopathic Pulmonary Fibrosis" jointly issued by the American Thoracic Society / European Respiratory Association / Japanese Chest Association / Latin American Chest Association in 2015 One of the two drugs with the highest recommendation level (conditional recommendation).

(Two) non-drug treatment

Quit smoking: Most patients with IPF are smokers, and smoking is related to the occurrence of disease. Smokers must persuade and help patients to quit smoking. oxygen therapy. Mechanical ventilation. Pulmonary rehabilitation . lung transplantation.

Idiopathic pulmonary fibrosis prevention

1. Due to the slow course of the disease, medical staff should carefully check the diagnosis.

2. Patients should be encouraged to build confidence in defeating the disease, actively cooperate with treatment, and adhere to treatment.

3. Strengthen physical exercise and disease resistance, and keep warm in winter.

4. Pay attention to adjusting the diet to increase nutrition; smokers must quit smoking.