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Idiopathic Pulmonary Fibrosis (Clinical Presentation (Arthralgia, Cyanosis…
Idiopathic Pulmonary Fibrosis
Key Facts
The most common of the idiopathic pulmonary pneumonias
There is patchy fibrosis of the interstitial and minimal or absent inflammation, acute fibroblastic proliferation and collagen deposition
Commonest cause of interstitial lung disease
Also known as cryptogenic organising pneumonia
Type of interstitial lung disease
Epidemiology
Mean onset is in the sixties and presentation is very uncommon under the age of 50
Males are twice as likely to be affected
A progressive chronic pulmonary fibrosis of unknown aetiology although 20% of patients give a history of occupational exposure to metals and wood dusts
Pathophysiology
It is thought that repetitive injury to the alveolar epithelium, caused by currently unidentified environmental stimuli leads to the activation of several pathways responsible for repair of the damaged tissue
However in IPF, the wound healing mechanisms become uncontrolled, leading to the over-production of fibroblasts and deposition of increased extracellular matrix in the interstitial with little inflammation
The pathogenesis of IPF is unknown
The structural integrity of the lung parenchyma is therefore disrupted; there is loss of elasticity and the ability to perform gas exchange is impaired, leading to progressive respiratory failure
Risk Factors
Occupational dust exposure (metals, woods)
Drugs - methotrexate, imipramine
Infectious agents (CMV, Hep C, EBV)
Chronic GORD
Cigarette smoking
Genetic predisposition
Factors implicated in triggering the aberrant wound healing include:
Clinical Presentation
Arthralgia
Cyanosis
Weight loss
Finger clubbing
Malaise
Fine bi-basal end-inspiratory crackles
Exertional dyspnoea
Step-wise deterioration can occur due to pneumothorax, PE or intercurrent infection
Dry cough with/without sputum
There is variable interstitial inflammatory infiltrate in the affected areas of the lung with collapse of the lung architecture and the development of mystically dilated spaces within the fibrotic areas of the lung
But acute exacerbations with no identifiable cause are well recognised and are associated with increased mortality
This pattern of disease is characterised patchy with the sub-pleural regions of the lower lobes predominantly affected
The majority of patients with IPF show a pattern of lung disease described as usual interstitial pneumonitis (UIP)
Differential Diagnosis
COPD, asthma, bronchiectasis, congestive heart failure, atypical pneumonia, lung cancer, asbestosis & hypersensitivity pneumonitis
Diagnosis
High-resolution CT
More sensitive than CXR and is an essential tool for diagnosis
Confident diagnosis can be made if any of these are seen: basal distribution, sub pleural reticulation, traction bronchiectasis, honeycombing
Spirometry/Respiratory function test - shows a restrictive pattern
CXR
Small volume lungs with increased reticular shadowing at the bases
May be normal in early disease
Blood tests
Raised CRP
Raised immunoglobulins
Arterial blood gas - low PaO2, if severe then high PaCO2 too
Check antinuclear antibodies (ANA) and rheumatoid factor (RF) to exclude autoimmune rheumatic disease
Lung biopsy may be required - will see histological changes that are referred to as usual interstitial pneumonia
Aims of investigation in IPF are to confirm the presence of pulmonary fibrosis and exclude identifiable causes
Treatment
Treat GORD since it contributes to repetitive alveolar epithelial damage
Treat cough
Best supportive care - oxygen, pulmonary rehabilitation, palliative care
Pirfenidone - an antifibrotic agent that can slow the rate of FVC decline
Serial lung function testing is used to monitor disease progression
Lung transplant
Median survival time is 2-5 years
DO NOT GIVE HIGH-DOSE STEROIDS unless diagnosis of IPF is in doubt