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The pathophysiology of asthma is heterogeneous, but a division into T2-high and T2-low endotypes (marked by high and low levels of classic Th2 cytokines, including IL-4, IL-5, and IL-13, respectively) has been shown to be important regarding the selection of therapies.

Allergic asthma falls into the T2-high endotype, as do late-onset T2-high asthma and aspirin/NSAID-associated respiratory disease.

T2-low asthma phenotypes include nonallergic asthma, which tends to occur in adults and be marked by neutrophilic inflammation and variable response to standard therapies.


Azithromycin may be used to effectively treat diffuse panbronchiolitis; it may also slow down the progression of bronchiolitis obliterans syndrome in lung transplant recipients.


Procalcitonin is not recommended as a “rule-out” test for bacterial pneumonia; studies have not found a threshold at which bacterial pneumonia can be reliably distinguished from viral pneumonia based on procalcitonin levels.

Empiric antibacterial agents are recommended regardless of procalcitonin level at time of presentation.

Based on limited data and because of the potential for complications (eg, hyperglycemia), the IDSA/ATS guidelines recommend against corticosteroids in the treatment CAP of any severity.

Corticosteroids are recommended for patients with CAP who may also have severe septic shock, acute exacerbation of asthma or COPD, or adrenal insufficiency.

Pulmonary Tuberculosis

In view of the rapidity of rifampin resistance identification, the World Health Organization issued continued guidance in 2020 that rapid molecular testing is the ideal initial test for diagnosis and resistance profiling in persons in whom pulmonary or extrapulmonary tuberculosis is suspected.

Pulmonary Venous Thromboembolism

Direct-acting oral anticoagulants are recommended as first-line anticoagulation for most patients.

Discontinuation of anticoagulation may be considered after 3 months for patients

  • – With major transient/reversible risk factors (such as fracture of lower limb; hip or knee surgery)

  • – Who were hospitalized because of heart failure, atrial fibrillation, or myocardial infarction.

Guidelines support systemic thrombolysis for high-risk or massive PE (hemodynamically unstable) with low risk of bleeding.

Intermediate-risk or submassive PE patients have a significant decrease in incidence of hemodynamic collapse but do not have a mortality benefit with thrombolytic therapy.

They do, however, have an increase in major hemorrhagic complications, including intracranial hemorrhage.

Pulmonary Hypertension

A 2020 expert consensus survey has provided recommendations for treatment using oral prostacyclin analogs.

Radiation Lung Injury

Months to years after radiation therapy, an occasional patient will experience “radiation recall,” an inflammatory reaction in the radiated region after treatment with immune checkpoint inhibitors.


A 2020 study demonstrated that a moderate ...

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