Pulmonology · USMLE Step 1 and Step 2

Asthma song

Asthma - Pathophysiology & Treatment, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Asthma

Full song on YouTube ↗Spotify ↗

Key points in this song10

Asthma is a chronic inflammatory airway disease characterized by reversible bronchoconstriction, airway hyperresponsiveness, and airway remodeling driven by Th2-mediated immune responses.
Allergen exposure activates dendritic cells that promote naive T-cell differentiation into Th2 cells, releasing IL-4, IL-5, and IL-13 as the central cytokines of allergic asthma.
IL-4 and IL-13 drive B-cell class switching to IgE production; IgE binds mast cells and basophils, sensitizing them for future allergen exposure.
Re-exposure to allergen cross-links IgE on mast cells, triggering degranulation and immediate release of histamine, leukotrienes (LTC4, LTD4, LTE4), and prostaglandin D2, causing the early-phase response within minutes.
The late-phase response occurs 4–12 hours after exposure and is driven by eosinophil recruitment via IL-5 and eotaxin, causing sustained inflammation and airway damage.
Eosinophils release major basic protein and eosinophil cationic protein, which directly damage airway epithelium and amplify airway hyperresponsiveness.
Airway remodeling in chronic asthma includes subepithelial fibrosis, smooth muscle hypertrophy and hyperplasia, goblet cell metaplasia, and increased mucus production, leading to irreversible airflow limitation over time.
Parasympathetic (muscarinic M3 receptor) activation causes bronchoconstriction and mucus secretion, while beta-2 adrenergic receptor stimulation causes bronchodilation — the basis for anticholinergic and beta-agonist therapy.
Aspirin-exacerbated respiratory disease results from COX-1 inhibition shunting arachidonic acid toward the 5-lipoxygenase pathway, overproducing bronchoconstricting leukotrienes — treated with leukotriene receptor antagonists like montelukast.
Intrinsic (non-allergic) asthma involves non-IgE-mediated triggers such as exercise, cold air, irritants, and viral infections activating mast cells and airway nerves directly, without Th2 sensitization.