Interstitial Lung Disease 1 - Clinical Aspects

Question 1

What actually is the interstitium?

Important structures/molecules?

Answer 1

Interstitium = stuff between the alveolar epithelial cells and capillary endothelial cells.
Contains connective tissue stuff like collagen, elastin, reticulin, ECM, other proteins.

Question 2

2 broad mechanisms of injury to interstitium?

Answer 2

Direct injury with response and repair.

Infiltration of interstitium.

Question 3

If inflammation / fibrosis is deposited in interstitium, what happens to the lung?
(compliance, volume, air flow, gas exchange, etc.)

Answer 3

(static) Compliance reduced.
(static) Lung volume reduced.
Airflow typically is preserved.
Gas exchange impaired - due to impaired diffusion and V/Q mismatch.

Question 4

4+ broad categories of interstitial lung disease (ILD)? (aka diffuse parenchymal lung disease -DPLD)

Answer 4

DPLD of known etiology - esp. drugs or collagen vascular disease.
Idiopathic Pulmonary Fibrosis (IPF).
Idiopathic other than IPF (including acute interstial PNA).
Granulomatous DPLD (esp. sarcoidosis).
Other - (eg. LAM)

Question 5

What are pneumoconioses?

Answer 5

Dust-induced diseases (eg. asbestosis, silicosis)

Question 6

What’s the basis of diagnosis of an interstitial lung disease?

Answer 6

Typically you need to get lots of different data points:
History and physical.
CXR and HRCT.
Lab data.
PFTs.
Histology.
Response to therapy.
(just like... many diseases)

Question 7

Typical symptoms of interstitial lung disease? (4 things)

Answer 7

Cough, usu. dry.
Dyspnea, esp with exertion.
Chest pain, wheezing, hoarseness.
Systemic symptoms: fever, joint pain, rashes, dysphagia etc.
(kind of a silly thing to list… lots of diseases, lots of different constellations of symptoms…)

Question 8

4 typical physical examine findings in interstitial lung disease?

Answer 8

Tachypnea, shallow breathing.
Dry, “velcro” crackles.
Clubbing of digits (present in up to 50% of cases).
Extrapulmonary finding.

Question 9

3 non-lung findings in CXR/HRCT that can help with Dx of interstitial lung disease?

Answer 9

Pleural effusion.
Pleural plaques.
Lymphadenopathy.

Question 10

Methods of biopsy?

Answer 10

Transbronchial - for stuff that runs near larger airways.

Surgical.

Question 11

What does “usual interstitial pneumonia” (UIP) refer to?

Answer 11

The pattern of damage seen in histology of IPF.

Question 12

Most sensitive HRCT finding for IPF?

Answer 12

Honeycombing.

and… UIP…?

Question 13

What does temporal heterogeneity refer to?

Answer 13

There are different lesions of varying ages in the biopsy sample - this is seen in IPF.

Question 14

Is IPF the only thing that can cause UIP?

Answer 14

Nope… other things like collagen vascular disease, drug exposure, chronic sensitivity, asbestosis etc. can cause UIP.

(UIP is very sensitive, but not specific for IPF)

Question 15

HRCT UIP is more specific for IPF than biopsy UIP.

Answer 15

Okay. But it’s still not 100%.

… but if you see UIP on both you can be pretty sure it’s IPF?

Question 16

Median survival for IPF?

Answer 16

3 years.

Treatments so far don’t seem to help.

Question 17

Age range for when people develop sarcoidosis?

Answer 17

Bimodal - peak in 20s, and peak in 50s.

Question 18

Histological “hallmark” of sarcoidosis?

Answer 18

Non-caseating granulomas.

Necessary, but not specific, for diagnosis.

Question 19

DDx for non-caseating granulomas?

Answer 19

Infection (mycobacteria, fungi)
Malignancy
Exposures: Beryllium, talc
Vasculidites: GPA, 
Hypersensitiviy pneumonitis

Question 20

Do most patients with sarcoidosis have symptoms?

Answer 20

Nope.

Question 21

Organ most commonly affected by sarcoidosis?

Answer 21

lungs (which is why we’re talking about it)… but it can hit pretty much everything else.

Question 22

When working up sarcoidosis…

Answer 22

check on all the organ systems it could affect.

Make sure it’s not TB, etc.

Question 23

3 forms of cutaneous sarcoidosis?

Answer 23

Cutaneous granulomatosis.
Erythema nodosum.
Lupus pernio.

Question 24

4 radiographic stages of sarcoidosis?

Answer 24

Stage 1: Bilateral hilar lymphadenopathy
Stage 2: Bilateral lymphadenopathy + parenchymal infiltrates.
Stage 3: Parenchymal infiltrates.
Stage 4: Advanced fibrosis.