2013-09-03 Interstitial Lung Dz: Pathophys, Clinical and Pathological Flashcards
What are the main categories of inhaled fibrosing lung dzs?
Two:
- Hypersensitivity Pneumonitis
- Pneumoconiosis
What are histo ∆s in ARDS?
ARDS causes the histo ∆ called “DAD” (Diffuse Alveolar Damage).
–Damage to alv. endothelium and epithelium; leaky—>fluid into interstitium and alveoli—>fibrin leaks out—>organized by fibroblasts leading to dense pink hyaline membranes in alv space
Type I pneumocytes (more fragile) die and are later repop’d by Type II; interstitial inflammation
–Causes include: 50% due to: sepsis, diffuse pulm infections, aspiration, trauma esp to head; other = AIP acute interstitial pneumonia which is an idiopathic DAD (a.k.a. Hamman-Rich syndrome)
What are histo ∆s in hypersenitivity pneumonitis? How are they named?
granulomatous inflammation (poorly formed granulomas), thickened interstitium
can also see scattered eosins, late stage fibrosis and obliterated bronchioles
Usually named after substance/occupation causing the hypersensitivity
What pathophysiological similarities do ILDs share?
–restrictive dzs on PFT
What pathophys differences differentiate different ILDs?
Four major categories:
- ILD of known cause
- Granulomatous ILD
- Idiopathic ILD (e.g. sarcoidosis and hypersens pneumonitis)
- All others
What is IPF?
IPF (Idiopathic Pulmonary Fibrosis) is clinical term for pathophysiologic process of UIP (usual interstitial pneumonia).
Tell me about UIP.
UIP (usual interstitial pneumonia) is one of the idiopathic ILDs. (There are 6 other non-UIP ILDs)
- -UIP is patho term for IPF (idio. pulm. fibr.)
- -Histo: fibroblast foci which may have a new layer of pneumocytes re-epithelizing on top
- -Patchwork idea: these fibroblast foci are due to temporally heterogenous insults
What is the final common manifestation of all fibrosing lung dzs?
Honey Comb Lung
- -Little no resp/ f(x) at these sites
- -Type I pneumocytes permanently gone
What are types of pneumoconiosis?
Coal Miner’s Lung; Silicosis; Asbestosis
What is the main progression of events in lung fibrosis development?
Little confused as to how applicable this is to whole picture…
Interstitial Thickening: Fibroblasts inside the interstitium are activated
Endothelial/Epithelial Injury
- Leaky endothelium
- Fibrin leaks out
- Fibroblasts organize
Can also have:
Granulomatous Inflammation
**POINT: mostly a fibrotic (vs. inflammatory) process for most types of ILD (thus the poor response to steroid therapy)
What is Caplan Syndrome?
RA + pneumoconiosis = more severe progressive fibrosis
What histo ∆s are seen in Coal Miner’s lung?
- -Anthracosis
- -macules of 1-2mm with C-laden M0s.
- -nodular fibrosis
COMPLEX DZ:
- -coalescence of fibr. nodules
- -PMF (in Coal Miners usu. due to silica + coal dust)
What histo ∆s are seen in Silicosis?
Two types of silica inhaled: crystalline (quartz) w/ rigid edges that are more fibrogenic than amorphous (talc) which is more readily cleared.
Early Dz: Nodular scars +/- anthracosis
Complex Dz: Nodular coalescence and PMF
ACUTE Dz: protein-rich fluid leaks into the alveolar spaces
What histo ∆s are seen in Asbestosis?
Also two types (serpentine is safer, amphibole is worse)
causes diffuse interstitial fibrosis; iron-coated bodies w/in M0s
What are histo ∆s in sarcoid?
10-15% of Sarcoid pts progress to have lung dz
–non-necrotizing granulmoas is major finding
What are major s/sx in ILD?
sx: cough (possibly due to irritation of C-fibers by interstitial inflamm) & dyspnea (multifactoral: incr work of breathing and probs some vagal stim; some of the worst dyspnea pts have ILD)
s: fine crackles
- -rapid shallow breathing
- -clubbing
- -findings of other disorder (e.g. rheumatologic) that is causing ILD
Describe the role of enviro and occu factors in the development of ILD.
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Explain the pathophys of ILD, partic. as related to resp mech and gas exchange and…
Explain how the f(x)al abnormalities in ILD are related to structural abnormalities.
–decr. compliance (b/c of incr collagen in/stiffness of interstitium)
–diffusion impairment (b/c of thickening of interstitium, and decr surf. area)
–V/Q mismatch (b/c heterogenous effects on lungs; V/Q mismatch is the major driver of hypoxemia in pts with ILD NOT the diffusion impairment)
–exercise-induced de-sat (1: b/c of faster transit thru capillarie so this is where diffusion impairment causes hypox; 2: also b/c “during exercise,themixed venous oxygen saturation (SvO2) drops, and in the
setting of V/Qmismatch (i.e. low V/Q) orshunt,the drop in SvO2 causesthe hypoxia to worsen.
A simple way to think of it asfollows: in the setting ofshunt,the shunted fraction of blood flow
(which has a PO2 and saturation equalto venous blood)mixes with the oxygenated blood;the
lowerthe saturation (and content) of venous blood (as occurs during exercise),themore it will
lowerthe saturation (and content) ofthe oxygenated blood with which itmixes.”
Imaging in classification and dx of ILD.
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Clinical syndrome (incl pathophys, prognosis and tx) of IPF.
IPF = Idiopathic Pulmonary Fibrosis (= UIP histologically, though UIP can appear in syndromes other than IPF! gah)
PATHOPHYS
Fibroblastic proliferation
Describe clinical syndrome of sarcoidosis.
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Role of anti-inflammatory rx in tx of various forms of ILD.
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Describe palliation of sx in advanced ILD.
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