2013-09-03 Interstitial Lung Dz: Pathophys, Clinical and Pathological

Question 1

What are the main categories of inhaled fibrosing lung dzs?

Answer 1

Two:

1. Hypersensitivity Pneumonitis
2. Pneumoconiosis

Question 2

What are histo ∆s in ARDS?

Answer 2

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)

Question 3

What are histo ∆s in hypersenitivity pneumonitis? How are they named?

Answer 3

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

Question 4

What pathophysiological similarities do ILDs share?

Answer 4

–restrictive dzs on PFT

Question 5

What pathophys differences differentiate different ILDs?

Answer 5

Four major categories:

1. ILD of known cause
2. Granulomatous ILD
3. Idiopathic ILD (e.g. sarcoidosis and hypersens pneumonitis)
4. All others

Question 6

What is IPF?

Answer 6

IPF (Idiopathic Pulmonary Fibrosis) is clinical term for pathophysiologic process of UIP (usual interstitial pneumonia).

Question 7

Tell me about UIP.

Answer 7

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

Question 8

What is the final common manifestation of all fibrosing lung dzs?

Answer 8

Honey Comb Lung

• -Little no resp/ f(x) at these sites
• -Type I pneumocytes permanently gone

Question 9

What are types of pneumoconiosis?

Answer 9

Coal Miner’s Lung; Silicosis; Asbestosis

Question 10

What is the main progression of events in lung fibrosis development?

Answer 10

Little confused as to how applicable this is to whole picture…

Interstitial Thickening: Fibroblasts inside the interstitium are activated

Endothelial/Epithelial Injury

1. Leaky endothelium
2. Fibrin leaks out
3. 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)

Question 11

What is Caplan Syndrome?

Answer 11

RA + pneumoconiosis = more severe progressive fibrosis

Question 12

What histo ∆s are seen in Coal Miner’s lung?

Answer 12

• -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)

Question 13

What histo ∆s are seen in Silicosis?

Answer 13

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

Question 14

What histo ∆s are seen in Asbestosis?

Answer 14

Also two types (serpentine is safer, amphibole is worse)

causes diffuse interstitial fibrosis; iron-coated bodies w/in M0s

Question 15

What are histo ∆s in sarcoid?

Answer 15

10-15% of Sarcoid pts progress to have lung dz

–non-necrotizing granulmoas is major finding

Question 16

What are major s/sx in ILD?

Answer 16

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

Question 17

Describe the role of enviro and occu factors in the development of ILD.

Answer 17

.

Question 18

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.

Answer 18

–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.”

Question 19

Imaging in classification and dx of ILD.

Answer 19

.

Question 20

Clinical syndrome (incl pathophys, prognosis and tx) of IPF.

Answer 20

IPF = Idiopathic Pulmonary Fibrosis (= UIP histologically, though UIP can appear in syndromes other than IPF! gah)

PATHOPHYS
Fibroblastic proliferation

Question 21

Describe clinical syndrome of sarcoidosis.

Answer 21

.

Question 22

Role of anti-inflammatory rx in tx of various forms of ILD.

Answer 22

.

Question 23

Describe palliation of sx in advanced ILD.

Answer 23

.