What is Idiopathic Pulmonary Fibrosis (IPF)?

Idiopathic Pulmonary Fibrosis (IPF): Definition and Characteristics

Idiopathic Pulmonary Fibrosis (IPF) is a specific form of chronic, progressive, fibrosing interstitial pneumonia of unknown cause, limited to the lungs, occurring primarily in older adults, and characterized by the histopathological pattern of usual interstitial pneumonia (UIP). 1

Definition and Pathophysiology

• IPF is defined by a specific histopathological pattern called usual interstitial pneumonia (UIP), which is characterized by heterogeneous appearance of areas of fibrosis with scarring and honeycomb change alternating with areas of less affected or normal parenchyma 1

• The disease involves repetitive micro-injury to lung tissue and vasculature, triggering an inflammatory cascade and progressive fibrosis that destroys lung architecture, reduces compliance, and compromises gas exchange 2, 3

• The etiology remains unknown, but risk factors include:

  • Older age (typically 60-70 years) 1
  • Male gender 1
  • History of cigarette smoking 1
  • Gastroesophageal reflux 1
  • Possible viral infections (Epstein-Barr virus, hepatitis C) 1
  • Genetic predisposition (approximately 30% of patients have genetic factors that increase risk) 1

Clinical Presentation

• The typical presentation includes:

  • Insidious onset of progressive exertional dyspnea 1
  • Dry, nonproductive cough that is often refractory to antitussive agents 1
  • Bibasilar inspiratory "Velcro" crackles on auscultation (present in >80% of patients) 1
  • Digital clubbing (present in <50% of cases) 1

• The disease typically presents in the sixth and seventh decades of life, with patients younger than 50 years being rare 1

• Weight loss and alteration of general status are uncommon; cyanosis and signs of right ventricular failure only occur in advanced stages 1

Diagnostic Criteria

• The definite diagnosis of IPF requires:

  1. Exclusion of other known causes of interstitial lung disease (drug toxicities, environmental exposures, connective tissue diseases) 1
  2. Abnormal pulmonary function studies showing restriction and/or impaired gas exchange 1
  3. Characteristic abnormalities on chest radiographs or high-resolution computed tomography (HRCT) scans 1

• HRCT findings typical of UIP pattern include:

  • Bibasilar reticular abnormalities with minimal ground glass opacities 1
  • Honeycombing with or without traction bronchiectasis 1
  • Predominantly peripheral and basal distribution 1

• Surgical lung biopsy is recommended in patients with suspected IPF who have clinical, physiological, or radiological features that are not typical for IPF 1

Disease Course and Prognosis

• IPF is characterized by progressive worsening of dyspnea and lung function with poor prognosis 1, 2

• Median survival is estimated between 2-4 years after diagnosis without treatment 1, 4

• The disease course is variable, but IPF progresses in a relentless manner that may be difficult to detect using symptoms, chest radiographs, or spirometry alone 1

• Respiratory failure is the most frequent cause of death, accounting for approximately 40% of deaths in patients with IPF 1

• Patients with IPF have an increased risk (10-15%) of developing bronchogenic carcinoma 1

Management Approach

• Treatment options include:

  • Antifibrotic medications (nintedanib and pirfenidone) that can slow disease progression 1
  • Oxygen supplementation and pulmonary rehabilitation 1
  • Management of comorbidities (pulmonary hypertension, gastroesophageal reflux, obstructive sleep apnea, lung cancer) 1
  • Palliative care for symptom management 1

• Lung transplantation is the only intervention shown to improve survival and should be considered for patients who experience progressive deterioration 1, 5

• Patients should be evaluated every 3-6 months or more often for disease progression 1

• Acute exacerbations may be treated with corticosteroids 1

Important Distinctions

• IPF must be distinguished from other interstitial lung diseases such as nonspecific interstitial pneumonia (NSIP), desquamative interstitial pneumonia (DIP), respiratory bronchiolitis-associated interstitial lung disease (RBILD), lymphoid interstitial pneumonia (LIP), acute interstitial pneumonia (AIP), and idiopathic bronchiolitis obliterans organizing pneumonia (idiopathic BOOP) 1

• The diagnosis requires exclusion of other forms of interstitial lung disease with identified causes (hypersensitivity pneumonitis, drug toxicity, pneumoconiosis, cancer) or occurring in specific contexts (connective tissue disease, sarcoidosis) 1