interstitial lung disease
aka diffuse parenchymal lung disease
disease of the alveolar wall, including the interstitium, the potential space between the basement membranes of the alveolar epithelium and the capillary endothelium
may also involve the alvolar space and small airways
four categories of ILDs
ILDs of known cause or association
idiopathic interstitial pneumonias
granulomatous ILDs
other (rare) DPLDs
interstitial lung diseases with a known cause
pneumoconiosis - exposure to inorganic dusts
hypersensitivity pneumonitis - immunologic response to inhaled organic dusts
reactions to chemicals, drugs, radiation, and toxic gases
those associated with connective tissue disease
proposed pathogenesis of ILD
age related susceptible lung
wound clot
aberrant epithelial cell activation
fibroblast focus
epithelial-mesenchymal transition
hypercoagulable milieu
exaggerated ECM accumulation
progressive lung remodeling
honeycomb changes
categories of idiopathic interstitial pneumonias
chronic fibrosing IIP
smoking-related IIP
acute/subacute IIP
chornic fibrosing IIPs
idiopathic pulmonary fibrosis (IPF)
idiopathic nonspecific interstitial pneumonia (NSIP)
smoking-related IIPs
respiratory bronchiolitis - interstitial lung disease (RB-ILD)
desquamative interstitial pneumonia (DIP)
acute/subacute IIPs
cryptogenic organizing pneumonia (COP
acute interstitial pneumonia (AIP)
symptoms of ILD
exertional dyspnea, usually insiduous
cough, usually non-productive
physical findings of ILD
fine, end-inspiratory crackles ("Velcro rales)
digital clubbing (IPF)
cyanosis
signs of cor pulmonale increased P2, RV lift, R-sided S3, JVD, edema (advanced disease)
findings on ILD chest x-ray
10% are normal at initial presentation
reticular, nodular, or reticulo-nodular interstitial pattern
diffuse and patchy alveolar pattern
reticular pattern
indicative of IPF
nodular pattern
indicative of sarcoidosis
alveolar pattern
much more homogeneous and confluent
common abnormalities of IL on HRCT
reticular opacities
nodular opacities
ground glass opacities
traction bronchiectasis
honeycomb cysts
traction bronchiectasis
bronchi are bigger than expected for specific lung sizes due to airways being pulled open
reticular opacities
indicative of scleroderma
nodular opacities
suggestive of sarcoidosis
ground glass opacities
suggests hypersensitivity pneumonitis
honeycomb cysts
suggestive of IPF
pulmonary function test results for ILD
restrictive defect most common
decreased lung volumes (TLC, FRC, RV)
normal or elevated FEV1/FVC
decreased lung compliance
reduced diffusion capacity
mixed restrictive and obstructive defect possible
arterial blood gas for ILD
increased A-a gradient, decreased PaO2
pneumoconiosis
ILD caused by inorganic dusts
silica -> silicosis
coal dust -> coal workers pneumoconiosis
asbestos -> asbestosis
hard metal alloys -> giant cell pneumonitis
berylium 0> berylliosis
hypersensitivity pneumonitis (HP)
ILD caused by inhalation of organic dusts
moldy hay -> farmer's lung
bird proteins -> bird fancier's disease
drugs that can cause ILD
chemotherapeutic agents (bleomycin, busulfan, methotrexate)
antibiotics (nitrofurantoin)
drug-induced lupus (hydralazine, procainamide)
miscellaneous (gold salts, amiodarone)
connective tissue diseases that can lead to ILD
rheumatoid arthritis
systemic lupus erythematosis
progressive systemic sclerosis (scleroderma)
Sjogren's syndrome
polymyositis and dermatomyositis
mixed connective tissue disease
anylosing spondylitis
idiopathic pulmonary fibrosis (IPF)
unknown cause, limited to the lungs
more common in men, usually for people > 60 yrs old
risk factors include smoking and dust exposure
histologial pattern of UIP
no effective therapy
median survival 3-3.5 years
histologic findings for IPF
heterogeneit, alternating zones of interstitial fibrosis, inflammation, honeycombing, and normal lung
patchy thickening of alveolar septa
fibroblastic foci with scant inflammation
honeycomb lung, broad bands of firosis with little inflammation, no remaining alveoli - end stage disease
idiopathic nonspecific interstitial pneumonia (NSIP)
associated with auto-immune phenomena
more common in women
smoking not a risk factor
usually diagnosed in middle age
may respond to steroids and other immunosuppressive treatments
prognosis better than IPF
histologic findings in NSIP
cellular and fibrotic variations
a lot more inflammatory cells in cellular
less so in fibrotic
don't see honeycomb cysts
