Idiopathic pulmonary fibrosis overview

# Overview
Idiopathic pulmonary fibrosis (IPF) is a progressive fibrosing disease of the interstitial lung diseases which leads to irreversible decline in the lung functions for unknown cause. IPF is one of the interstitial lung disease and particularly is a subtype of idiopathic interstitial pneumonia. Pulmonary fibrosis share the pathogenesis process of interstitial lung disease which involve the pulmonary parenchyma. Although the exact pathogenesis is not fully understood, there are many initiating factors which cause the pulmonary tissue injury. The main features of the lung injury includes inflammation, fibrosis, and granulomas development. Common causes of pulmonary fibrosis include autoimmunity, rheumatoid arthritis, scleroderma, tuberculosis, SLE, sarcoidosis, and polymyositis. Other causes of pulmonary fibrosis include environmental factors as cigarette smoking and dust exposure. Idiopathic pulmonary fibrosis must be differentiated from other causes of interstitial lung diseases which may cause fibrosis as well. Prevalence of idiopathic pulmonary fibrosis ranges from a low of 0.5 per 100.000 persons to a high of 27.9 per 100.000. Incidence of idiopathic pulmonary fibrosis ranges from a low of 3 per 100,000 persons to a high of 9 per 100,000 persons. Common risk factors of pulmonary fibrosis include cigarette smoking and genetic mutations which include hTERT, MUC5B, TERT, and RTEL1. Other risk factors include GERD and wood dust. If left untreated, idiopathic pulmonary fibrosis will lead to complete respiratory failure and death. Common complications of idiopathic pulmonary fibrosis include pulmonary hypertension, lung cancer, and cardiovascular comorbidities. The prognosis of idiopathic pulmonary fibrosis is usually poor with a survival rate from 2 to 5 years. Common symptoms of idiopathic pulmonary fibrosis include Dyspnea, cough, Clubbing, Crackles, and arthralgia. Physical examination of patients with occupational lung disease is usually remarkable for bronchial breathing, increased vocal resonance, and fine crepitations. On chest CT scan, Idiopathic pulmonary fibrosis is characterized by honeycombing appearance of the lungs, bronchiectasis, ground glass opacities, and distortion of the lung opacities. The mainstay of the therapy is supportive care measures as mechanical ventilation. Lung transplantation is essential in treatment of patients with idiopathic pulmonary fibrosis. Pulmonary fibrosis is the most common interstitial lung disease requiring lung transplant and it should be performed early in order to increase the survival rate.

# Historical Perspective
Pulmonary fibrosis was first described by Dr. Von Buhl in 1872. Dr. Rindfleish reported a case of a 40 year old patient who presented with worsening cough and dyspnea and he named this case as "Cirrhosis cystica pulmonum" in 1898.

# Classification
Idiopathic pulmonary fibrosis is a disease among a large group of the interstitial lung diseases and particularly a subtype of the idiopathic interstitial pneumonia. The major group Acute Interstitial Pneumonia (AIP), Cryptogenic Organizing Pneumonia (COP), Respiratory BronchiolitisInterstitial Lung Disease (RB-ILD), and Desquamative Interstitial Pneumonia (DIP).

# Pathophysiology
Pulmonary fibrosis share the pathogenesis process of interstitial lung disease which involve the pulmonary parenchyma. Although the exact pathogenesis is not fully understood, there are many initiating factors which cause the pulmonary tissue injury. The main features of the lung injury includes inflammation, fibrosis, and granulomas development.

# Causes
Common causes of pulmonary fibrosis include autoimmunity, rheumatoid arthritis, scleroderma, tuberculosis, SLE, sarcoidosis, and polymyositis. Other causes of pulmonary fibrosis include environmental factors as cigarette smoking and dust exposure.

# Differentiating Idiopathic Pulmonary Fibrosis from Other Diseases
Idiopathic pulmonary fibrosis must be differentiated from other causes of interstitial lung diseases which may cause fibrosis as well. Other diseases may include acute interstitial pneumonia, hypersensitivity pneumonia, occupational lung diseases, and pulmonary hemorrhage diseases.

# Epidemiology and Demographics
Prevalence of idiopathic pulmonary fibrosis ranges from a low of 0.5 per 100.000 persons to a high of 27.9 per 100.000. Incidence of idiopathic pulmonary fibrosis ranges from a low of 3 per 100,000 persons to a high of 9 per 100,000 persons. The prevalence of idiopathic pulmonary fibrosis increases with age. Idiopathic pulmonary fibrosis is more prevalent in men more than women.

# Risk Factors
Common risk factors of pulmonary fibrosis include cigarette smoking and genetic mutations which include hTERT, MUC5B, TERT, and RTEL1. Other risk factors include GERD and wood dust.

# Screening
There is insufficient evidence to recommend routine screening for idiopathic pulmonary fibrosis.

# Natural History, Complications, and Prognosis
If left untreated, idiopathic pulmonary fibrosis will lead to complete respiratory failure and death. Common complications of idiopathic pulmonary fibrosis include pulmonary hypertension, lung cancer, and cardiovascular comorbidities. The prognosis of idiopathic pulmonary fibrosis is usually poor with a survival rate from 2 to 5 years.

# Diagnosis

## Diagnostic Study of Choice
The diagnostic criteria for IPF includes major criteria and minor criteria. The major criteria must include exclusion of other causes of interstitial lung disease, pulmonary function tests that is evident of lung fibrosis, bibasilar reticular abnormalities in CT lung, and lung biopsy shows fibrosis. The minor criteria should include 3 of 4 criterion as age > 50, duration of illness more than 3 months, bibasilar inspiratory crackles, and insidious onset of exertional dyspnea.

## History and Symptoms
Common symptoms of idiopathic pulmonary fibrosis include Dyspnea, cough, Clubbing, Crackles, and arthralgia. Less common symptoms include Hamman-Rich Syndrome.

## Physical Examination
Patients with idiopathic pulmonary fibrosis usually appear fatigued and short of breath. Physical examination of patients with idiopathic pulmonary fibrosis is usually remarkable for bronchial breathing, increased vocal resonance, and fine crepitations.

## Laboratory Findings
There are no diagnostic laboratory findings associated with pulmonary fibrosis. However, useful laboratory findings consistent with the diagnosis of pulmonary fibrosis include abnormal arterial blood gases, sputum analysis, and blood picture.

## X-ray
X ray imaging does not show specific features for idiopathic pulmonary fibrosis. However, patients with idiopathic pulmonary fibrosis have imaging abnormalities from the beginning of the disease course.

## CT scan
On chest CT scan, Idiopathic pulmonary fibrosis is characterized by honeycombing appearance of the lungs, bronchiectasis, ground glass opacities, and distortion of the lung opacities.

## MRI
There are no MRI findings associated with idiopathic pulmonary fibrosis.

## Other Imaging Findings
There are no other imaging findings associated with idiopathic pulmonary fibrosis.

## Other Diagnostic Studies
Other diagnsotic findings consistent with diagnosis of idiopathic pulmonary fibrosis include reduced lung volumes and decreased diffusion capacity of carbon monoxide. Both are performed via spirometry.

# Treatment

## Medical Therapy
The mainstay of therapy for idiopathic pulmonary fibrosis is the supportive care measures which include mechanical ventilation, pulmonary rehabilitation, and vaccination against influenza and pneumococcus. Medical treatment as nintedanib and pirfenidone can be administrated to slow the disease progression.

## Surgery
Lung transplantation is essential in treatment of patients with idiopathic pulmonary fibrosis. Pulmonary fibrosis is the most common interstitial lung disease requiring lung transplant and it should be performed early in order to increase the survival rate.

## Primary Prevention
The primary prevention of pulmonary fibrosis or usual interstitial pneumonia includes smoking cessation and vaccination against influenza.

## Secondary Prevention
The primary and secondary prevention strategies for idiopathic pulmonary fibrosis are the same.