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Respiratory system

Apnea and hypoventilation

Apnea of prematurity

Sleep apnea

Pleura and pleural space disorders


Pleural effusion





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USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

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A 58-year-old man goes to the emergency department for evaluation of fever and dry cough for the past week. He has also become progressively more dyspneic, and walking a single block makes him short of breath. He underwent a liver transplantation 4-months ago for treatment of autoimmune hepatitis and is currently taking several immunosuppressant drugs. Temperature is 38.5°C (101.3°F), pulse is 104/min, respirations are 20/min, blood pressure is 122/88 mmHg, and oxygen saturation is 89% on room air. Lung auscultation reveals bilateral crackles and rhonchi. Chest radiograph reveals bilateral, diffuse interstitial infiltrates extending from the perihilar region. Leukocyte count is 13,000/mm3 and serum lactate dehydrogenase level is 460 U/L. Further testing is most likely to reveal which of the following findings?  

External References

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pneumonia p. 645

Anaerobic organisms

pneumonia caused by p. 175

Chlamydia spp p. 146

pneumonia p. 645

Chlamydia trachomatis p. 146

pneumonia p. 175

Chlamydophila pneumoniae p. 146

pneumonia p. 175

Currant jelly sputum p. 140, 182

Klebsiella pneumonia p. 655

Cytomegalovirus (CMV)

pneumonia p. 645

Escherichia coli p. 140

pneumonia p. 175

Giant cell pneumonia p. 166

Haemophilus influenzae p. 138

pneumonia p. 175

Influenza p. 165

pneumonia p. 645

Klebsiella spp p. 140

pneumonia p. 645

Legionella spp

pneumonia p. 645

Mycoplasma spp

pneumonia p. 645

pneumonia caused by p. 175


pneumonia in p. 146

Palivizumab p. 118

pneumonia prophylaxis p. 165

Pneumonia p. 645

acute respiratory distress syndrome p. 642

adenoviridae p. 160

chlamydiae p. 146

coccidioidomycosis p. 147

common causes p. 175

compliance in p. 631

Haemophilus influenzae p. 138

inhalational injury p. 640

Klebsiella pneumoniae p. 655

Mycoplasma pneumoniae p. 146

Pneumocystis jirovecii p. 150

proton pump inhibitors and p. 381

Pseudomonas aeruginosa p. 139

Q fever p. 145

readmissions with p. 261

Staphylococcus aureus p. 131

Streptococcus pneumoniae p. 132

Streptococcus agalactiae p. 133

VZV p. 160

Respiratory syncytial virus (RSV)

pneumonia p. 175, 645

Staphylococcus aureus p. 131

pneumonia p. 645

Streptococcus agalactiae (Group B strep) p. 133

pneumonia p. 175

Streptococcus pneumoniae p. 132

pneumonia p. 175, 645


pneumonia p. 175


Pneumonia is an infection in the lung tissue caused by microbes, and the result is inflammation.

The inflammation brings water into the lung tissue, and that extra water can make it harder to breathe.

During inhalation, air reaches your lungs by traveling down your trachea, then it continues through the bronchi and the bronchioles and ends up in the alveoli.

The alveoli are tiny air sacs that look like tiny clumps of grapes, that are wrapped up in a net of capillaries. This is where the majority of gas exchange happens in the lungs.

Oxygen leaves the air in the alveoli and crosses into the bloodstream while carbon dioxide leaves the bloodstream and is then exhaled out of the body.

Now, now in addition to air, you’re constantly breathing in other stuff, like microbes. But we’re usually good at protecting ourselves.

For example, we have mechanical techniques like coughing, a mucociliary escalator that lines the entire airway and moves out larger bacteria, and macrophages that are nestled deep inside the alveoli and ready to destroy anything that lands there.

But sometimes, a particularly nasty microbe might succeed in colonizing the bronchioles or alveoli, and when that happens - Congratulations! You’ve got pneumonia.

Those microbes typically multiply and cross over from the airways into the lung tissue, creating an inflammatory response.

The tissue quickly fills with white blood cells as well as proteins, fluid, and even red blood cells if a nearby capillary gets damaged in the process.


Pneumonia is an infection of the lungs that results in air sacs being filled with fluid. It may be caused by bacteria, viruses, or fungal infections. Pneumonia is either community-acquired, meaning a person got sick outside of a hospital or healthcare setting; or hospital-acquired, which is when a person gets it when they are already hospitalized for something else. Common symptoms of pneumonia can include fever, cough, chest pain, shortness of breath, and difficulty breathing. The severity of symptoms can range from mild to severe. Treatment for pneumonia typically involves drugs to kill the invading pathogen and supportive care such as oxygen therapy.


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  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 7/E (ENHANCED EBOOK)" McGraw Hill Professional (2014)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Pneumonia: update on diagnosis and management" BMJ (2006)
  6. "<i>Streptococcus pneumoniae</i>: Epidemiology, Risk Factors, and Clinical Features" Seminars in Respiratory and Critical Care Medicine (2005)
  7. "Community-acquired pneumonia" The Lancet (2015)
  8. "Intracellular Survival and Replication of &lt;i&gt;Legionella Pneumophila&lt;/i&gt; within Host Cells" YAKUGAKU ZASSHI (2008)
  9. "Epithelial Cells Infected with <i>Chlamydophila pneumoniae</i> ( <i>Chlamydia pneumoniae</i> ) Are Resistant to Apoptosis" Infection and Immunity (2001)

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