Pneumonia: Pathology review

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Pneumonia: Pathology review

Respiratory system


Pneumonia: Pathology review

USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

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A 32-year-old man presents to his primary care provider for evaluation of fatigue and a nonproductive cough, which developed one month ago. Medical history is notable for hypertension and HIV infection. The patient is uninsured and has limited access to healthcare. He has not traveled overseas and has been living in Ohio for the past five years. Temperature is 38.2°C (100.8°F), blood pressure is 148/83 mmHg, and pulse is 98/min. On physical examination, the lung fields are clear to auscultation. Verrucous lesions are present over the trunk and upper extremities. Abdominal examination is unremarkable. No oral mucosal lesions are identified. Which of the following best describes the microscopic appearance of the organism responsible for this patient’s symptoms?  


Two people came to your clinic one day.

Mariah is a 54-year-old smoker, who came in with with productive cough with yellow sputum and left-sided chest pain.

Physical examination reveals fever, tachycardia, and tachypnea. Her lung sounds are barely audible, but it had crackles at the left base.

Next is Jeremy, a 64-year-old man who was hospitalized for a stroke 2 weeks ago.

He recently developed a cough and right-sided chest pain.

He is tachycardic and has a fever of 38.4°C.

Examination reveals fremitus, decreased breath sounds, and dullness to percussion in the right lower lung field.

Chest x-rays were performed which showed a left lower lobe infiltrate in Mariah’s case, and a right lower lobe infiltrate in Jeremy’s.

Now, both people have pneumonia.

So pneumonia is an infection of the lung tissue.

Some microbes can overcome the innate defenses of the lungs and immune system to colonize the bronchioles or alveoli.

These pathogens then triggers an inflammatory response.

Inflammatory cells, such as white blood cells, dead bacteria, proteins and fluid from the damaged tissue, form a fluid called exudate which can be coughed up and expelled from the body.

However they can also accumulate in the lungs, filling up the alveoli.

We can divide pneumonia into “classic” pneumonia or “atypical pneumonia based on symptoms.

So with classical pneumonia, high yield symptoms might include dyspnea, or shortness of breath, fatigue, and fever.

Individuals might also develop pleuritic chest pain, which is characterized by sudden and intense sharp, stabbing, or burning pain in the chest when inhaling and exhaling; and productive cough with yellow sputum.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Fishman's Pulmonary Diseases and Disorders, 2-Volume Set, 5th edition" McGraw-Hill Education / Medical (2015)
  6. "Pneumonia: update on diagnosis and management" BMJ (2006)
  7. "Viral pneumonia" The Lancet (2011)
  8. "Community-acquired pneumonia" The Lancet (2015)

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