15 - Interstitial lung diseases Flashcards
Define interstitial lung disease
Lung parenchymal disorders with common clinical, radiological, physical and pathologic features (hallmark= involvement of the space between alveoli)
**hard to distinguish from one another, a lot of overlap
What are the contents of the interstitium?
Between alveoli:
- type I pneumocytes
- type II pneumocytes
- capillaries (capillary endothelium)
- interstitial cells
What is the underlying pathogenesis of interstitial lung disease?
“Alveolitis”; damage to pneumocytes and endothelial cells leads to leukocyte release of cytokines which mediate/stimulate interstitial fibrosis
What are the consequences of fibrosis in interstitial lung disease?
- decreased lung compliance
- decreased lung expansion during inspiration
- increased elastic recoil (a non compliant lung wants to always be in its original resting state and will have more recoil back to that state)
At what point in the pathogenesis is interstitial lung disease irreversible?
Fibrosis of the lung is irreversible
What are 5 main clinical symptoms seen in interstitial lung disease?
- dry cough
- dyspnea
- late inspiratory crackles, bibasilar
- cor pulmonal (pulmonary HTN -> right heart failure)
- bilateral reticulonodular infiltrates on chest xray
What are 5 categories of chronic interstitial lung disease?
- fibrotic
- granulomatous
- eosinophilic
- smoking-related
- “other” (e.g. pulmonary alveolar proteinosis)
What are 6 possible causes of fibrotic chronic interstitial lung disease?
- Usual interstitial pneumonia (idiopathic pulmonary fibrosis)
- nonspecific interstitial pneumonia (NSIP)
- cryptogenic organizing pneumonia (COP)
- collagen vascular diseases
- pneumoconiosis
- drug reactions
What are 2 possible causes of granulomatous chronic interstitial lung disease?
- sarcoidosis
- hypersensitivity pneumonitis
What are 3 known causes of interstitial lung disease?
-
occupational and environmental inhalants
*pneumoconiosis= mineral dusts
*hypersensitivity pneumonitis= organic dusts - drugs/toxins (chemo, antibiotics)
- infections (CMV, TB, mycoplasma)
What are 3 interstitial lung diseases with unknown causes?
- idiopathic pulmonary fibrosis
- sarcoidosis
- collagen vascular disorders/vasculitis (RA, SLE, Wegener’s, Goodpasture’s)
Define pneumoconioses
Umbrella term for several non-neoplastic lung diseases that appear in response to inhalation of dusts (coal, silica, asbestos)
**25% of chronic interstitial lung disease cases are pneumoconioses
What are the 4 main factors that affect the development of pneumoconioses?
- amount of dust retained in the lung parenchyma and airways
- size, shape, and buoyancy of particles
- particle solubility and physiochemical reactivity
- possible additional effects/other irritants (e.g. smoking)
What are the 2 main types of pneumoconioses?
- fibrogenic
- “coal workers’ pneumoconiosis”= carbon dust
- silicosis= crystalline silica dust
- asbestosis= asbestos fibers
- non-fibrogenic (e.g. from barium/tin)
Describe Coal Workers Pneumoconiosis (CWP)
- anthracotic (carbon) pigment from
- coal mines
- urban centers
- tobacco smoke
- anthracotic pigment in interstitial compartment and lymph nodes
- simple CWP
- complicated CWP
Describe simple CWP
- fibrous opacities < 1cm
- usually in upper lobes
- characterized by coal dust deposits adjacent to respiratory bronchioles
Describe complicated CWP
- fibrous opacities > 1 cm (with or without central necrosis)
- massive fibrosis= crippling lung disease (aka black lung disease)
- complications=
- cor pulmonale
- caplan syndrome (CWP with rhematoid nodules)
- NO increased incidence of TB/cancer
Describe silicosis
- nodular opacities with concentric layers of collagen
- can see polarizable quartz particles
- “egg shell” calcifications in hilar lymph nodes
- complications=
- cor pulmonale
- caplan syndrome
- increased risk for TB and cancer
Describe asbestos-related disease
- deposition in respiratory bronchioles, alveolar ducts, and alveoli
- ferruginous bodies= macrophages phagocytose asbestos fibers and coat them with ferritin (iron + protein)
What is shown in these photos?
Asbestos bodies
Describe hypersensitivity pneumonitis
- inhaled antigen producing granulomatous interstitial pneumonitis
- type III hypersensitivity reaction
- first exposure= IgG in serum
- second exposure= Ab + inhaled antigen -> immune complexes -> interstitial inflammation
- chronic exposure= type IV hypersensitivity (granuloma formation)
Describe sarcoidosis and its prevalence
- multisystem granulomatous disease
- comprises 25% of chronic interstitial lung disease cases
- AA:white ratio 10:1
- M:F ratio 1:2
- 70% < 40 years
- classic example= young african american female non-smoker
What are some lab/radiological findings of sarcoidosis?
- increased ACE levels
- hypercalcemia
- polyclonal gammopathy
- cutaneous anergy (lack of response to skin antigens because of CD4 T cell consumption)
- bilateral hilar adenopathy and reticulonodular shadows on chest xray
Describe idiopathic pulmonary fibrosis
- 15% of chronic interstitial lung disease cases
- M > F, 40-70 years
- broad encompassing term for a number of types of idiopathic interstitial pneumonias
- nonspecific symptoms (dyspnea, fever, fatigue, cough)
What is the pathophysiology of idiopathic pulmonary fibrosis?
- repeated injury to the lung causes alveolitis ->
- cytokine release causes interstitial fibrosis ->
- interstitial fibrosis -> irregular dilation of adjacent airways resulting in honeycomb lung
