A physician considers prescribing high-dose corticosteroids to a newly diagnosed IPF patient, reasoning that reducing lung inflammation should slow fibrosis. Based on IPF pathophysiology, this approach is:
ASound, since TGF-β is released by inflammatory cells and corticosteroids suppress TGF-β production.
BFlawed, because IPF is primarily a disease of aberrant epithelial repair, not inflammation; corticosteroids have been shown to be ineffective.
CSound, because corticosteroids promote alveolar epithelial cell regeneration and reepithelization.
DFlawed, but only because corticosteroids are insufficiently potent — stronger immunosuppressants would work.
The defining insight of IPF pathophysiology is that inflammation is a secondary feature, not the driver. The primary event is recurrent injury to type II alveolar epithelial cells (AT2 cells) with failure of normal wound resolution — driven by chronically elevated TGF-β and myofibroblast persistence, not by ongoing immune cell activity. This is why corticosteroids, which work in many inflammatory lung diseases, are ineffective in IPF. Options 0 and 3 both assume inflammation is the primary mechanism; option 2 misunderstands what corticosteroids do.
Question 2 Multiple Choice
What makes myofibroblasts in IPF particularly destructive compared to fibroblasts in normal wound healing?
AThey produce a more chemically stable form of collagen that is resistant to enzymatic degradation.
BThey activate the adaptive immune system, creating a self-reinforcing cycle of inflammation and scarring.
CThey are resistant to apoptosis and continue depositing collagen long after a normal wound would have resolved, because TGF-β remains chronically elevated.
DThey migrate into the bloodstream and cause systemic fibrosis beyond the lungs.
In normal wound healing, fibroblasts deposit provisional matrix and then undergo apoptosis once the wound resolves and TGF-β signaling is switched off. In IPF, TGF-β remains chronically elevated, driving fibroblasts to differentiate into myofibroblasts that are resistant to apoptosis. These cells keep secreting collagen indefinitely. The result is progressive accumulation of irreversible scar tissue — not because the initial injury was larger, but because the resolution mechanism that stops normal healing has failed.
Question 3 True / False
In IPF, diffusing capacity (DLCO) falls disproportionately relative to lung volumes because thickened alveolar walls impede oxygen diffusion across the gas exchange membrane.
TTrue
FFalse
Answer: True
Fibrosis thickens the alveolar walls, increasing the distance oxygen must diffuse from air to blood. This impairs gas exchange even before resting oxygen saturation fails, which is why exertional hypoxia is an early hallmark: during exercise, when oxygen demand rises and blood transit time through the capillary shortens, the thickened diffusion barrier becomes the limiting factor. DLCO drops earlier and more severely than FVC in IPF, reflecting the destruction of the gas exchange surface as the primary functional lesion.
Question 4 True / False
Because current antifibrotic drugs like pirfenidone target the TGF-β pathway, they can halt disease progression in IPF and restore lost lung function over time.
TTrue
FFalse
Answer: False
Pirfenidone and nintedanib slow the rate of FVC decline but do not halt progression or reverse existing fibrosis. This reflects the fundamental lesson of established fibrosis: once collagen is deposited and structural architecture is destroyed, the damage is permanent. These drugs reduce the rate of new scar accumulation; they cannot dissolve existing scar. This reinforces why early diagnosis matters — the goal is to intervene before the disease burden becomes irreversible, not to restore what has already been lost.
Question 5 Short Answer
Why does the distinction between 'disease of aberrant repair' and 'inflammatory disease' matter clinically for IPF treatment?
Think about your answer, then reveal below.
Model answer: If IPF were primarily inflammatory, anti-inflammatory treatments like corticosteroids should work — and they are used effectively in other inflammatory lung diseases. But in IPF, inflammation is a secondary feature. The primary driver is failed resolution of wound healing: TGF-β remains elevated, myofibroblasts persist and keep depositing collagen, and the normal apoptotic shutdown of wound healing never occurs. Targeting inflammation in this context has no effect on the underlying mechanism and exposes patients to steroid side effects without benefit. The pathophysiological classification directly dictates which therapeutic target is valid.
This is the central clinical implication of understanding IPF as a repair-failure disease. Many students assume any scarring lung disease should respond to immunosuppression. The IPF case teaches that mechanistic understanding of the primary driver — not just the observable pathology — must guide treatment selection.