Pulm| Pneumonia: Lobar, Broncho, and Interstitial

2.21 Pneumonia: Lobar, Broncho, and Interstitial Pulmonary system review for the USMLE Step 1 Exam Pneumonia is an infection of the lung parenchyma that deals with gas exchange Three classic patterns of pneumonia: lobar, bronchopneumonia, and interstitial pneumonia Lobar pneumonia involves a single lobe of the lung and has four stages: congestion, red hepatization, gray hepatization, and resolution Most commonly associated with strep pneumoniae, also caused by Legionella and Klebsiella Bronchopneumonia is an infection of the bronchi that leads to diffuse infection of adjacent alveoli Causative organisms include strep pneumoniae, klebsiella, H influenza, and staph aureus Interstitial pneumonia is an ongoing infection in the interstitial areas of alveolar walls Causative organisms tend to be different compared to other types of pneumonia and include Mycoplasma pneumoniae, Legionella, chlamydophilia bugs, Coxiella burnetti, and some viruses (influenza and RSV) On chest X-ray, lobar pneumonia shows haziness in a single lobe with sharp demarcation, while bronchopneumonia and interstitial pneumonia show more diffuse haziness throughout the lungs Interstitial pneumonia tends to be more indolent, and patients may have not so good looking lungs on chest X-ray but are up and walking around (walking pneumonia).