Fibrosing Lung Diseases (Restrictive)

Question 1

How are chronic interstitial lung diseases characterized and what is the shared hallmark of these disorders?

Answer 1

characterized by bilateral often patchy, pulmonary fibrosis, mainly affecting the walls of alveoli

hallmark is reduced lung compliance (stiff lung), which in turn increases effort to breathe (dyspnea)

Question 2

How does advanced chronic interstitial lung disease appear histologically?

Answer 2

diffuse scarring and gross destruction of the lung referred to as end stage or “honeycomb” lung

Question 3

Who most commonly presents with idiopathic pulmonary fibrosis (IPF)?

Answer 3

A.k.a. cryptogenic organizing alveolitis – males more commonly affected, disease of older adults, virtually never occurring before 50 years of age

Diagnosis of exclusion

Question 4

what is thought to be the cause of idiopathic pulmonary fibrosis (IPF)?

Answer 4

believed to result from repeated injury, and defective repair of alveolar epithelium

germline loss of telomerase function is associated with increased risk (cellular senescence)

likely involves excessive activation of profibrotic factors such as TGF-beta

Question 5

describe the typical clinical findings of idiopathic pulmonary fibrosis (IPF)

Answer 5

• increasing dyspnea on exertion
• dry, nonproductive cough
• end-inspiratory Velcro-like crackles
• hypoxemia, cyanosis, and clubbing late in the course

poor prognosis after diagnosis - lung transplant is only definitive therapy

Question 6

what is progressive massive fibrosis (PMF)?

Answer 6

aka complicated Coal Worker’s Pneumoconiosis (CWP) - extensive fibrosis, lung function compromised

once established, PMF progresses even in absence of further exposure

*however, no increase in frequency of lung carcinoma in coal miners (distinguishes CWP from both silica and asbestos exposures)

[note that PMF can also be applied to complicated silicosis or asbestosis]

Question 7

When does silicosis most often present following exposure?

Answer 7

insidious presentation is most common (10-30 years later)

also can present as accelerated (within 10 years) or rapid (weeks-months, rare)

simple silicosis (rounded opacities in upper lobes on CXR without associated symptoms) may appear after 15-20 years exposure

Question 8

what are the histological signs of silicosis? (2)

Answer 8

1. silicotic nodules: appear in upper zones of lung, concentrically arranged hyalinized collagen fibers with silica particles in center (“whorled” appearance)
2. calcification of hilar lymph nodes: common, “eggshell” pattern, may progress in absence of further exposure (progressive massive fibrosis/PMF occurs when these grow very large)

Question 9

why is silicosis associated with an increased susceptibility to tuberculosis?

Answer 9

Crystaline silica inhibits the ability of pulmonary macrophages to kill phagocytosis mycobacteria

*also increased risk of lung cancer and autoimmune connective tissue disorders

Question 10

How can you tell by chest radiograph if a patient has past exposure to asbestos?

Answer 10

Plural plaques – thickening or calcification along the parietal pleura, particularly along the lower lung fields, the diaphragm in the cardiac border

*only imply exposure (not pulmonary impairment) without additional manifestations