A 19-year-old man is brought to the emergency department by his college roommate due to a day of confusion, severe dyspnea, and cough productive of yellowish sputum streaked with blood. According to his roommate, the patient visited an urgent care clinic last week for fever, rhinorrhea, and malaise. He was diagnosed with a "viral infection" and given a prescription medication that seemed to improve his illness. He has no other medical issues, takes no other medications, and does not smoke cigarettes or drink alcohol. Temperature is 40 C (104 F), blood pressure is 124/75 mm Hg, pulse is 125/min, and respirations are 32/min. Lung auscultation shows bilateral crackles in the lung midfields. A 2/6 ejection systolic murmur is heard at the left upper sternal border. Extremities are warm with bounding peripheral pulses. Chest x-ray reveals alveolar infiltrates in the midlung fields bilaterally as well as several thin-walled cavities. Which of the following is the most likely cause of this patient's condition?

Question

A 19-year-old man is brought to the emergency department by his college roommate due to a day of confusion, severe dyspnea, and cough productive of yellowish sputum streaked with blood.  According to his roommate, the patient visited an urgent care clinic last week for fever, rhinorrhea, and malaise.  He was diagnosed with a "viral infection" and given a prescription medication that seemed to improve his illness.  He has no other medical issues, takes no other medications, and does not smoke cigarettes or drink alcohol.  Temperature is 40 C (104 F), blood pressure is 124/75 mm Hg, pulse is 125/min, and respirations are 32/min.  Lung auscultation shows bilateral crackles in the lung midfields.  A 2/6 ejection systolic murmur is heard at the left upper sternal border.  Extremities are warm with bounding peripheral pulses.  Chest x-ray reveals alveolar infiltrates in the midlung fields bilaterally as well as several thin-walled cavities.  Which of the following is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

This patient's fever, rhinorrhea, and malaise improved with an antiviral medication, which suggests he originally had influenza. However, after several days of improvement, he subsequently developed high fever, dyspnea, and cough, a characteristic chronology for secondary bacterial pneumonia. Secondary bacterial pneumonia is the most common complication of influenza. Although risk is greatest in patients age >65, secondary bacterial pneumonia with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) primarily occurs in young patients. CA-MRSA causes severe, necrotizing pneumonia that is rapidly progressive and often fatal. Manifestations include high fever, productive cough, hemoptysis, leukopenia, and multilobar cavitary infiltrates. Although heart murmur can indicate infectious endocarditis due to CA-MRSA bacteremia, flow murmurs are also common in young individuals with high fever. Most patients with MRSA pneumonia require admission to the intensive care unit and broad-spectrum, empiric antibiotics, including either vancomycin or linezolid. (Choice A) Aspergillus primarily affects immunocompromised patients and can cause the classic triad of fever, pleuritic chest pain, and hemoptysis. Multilobar nodular or cavitary infiltrates may occur. This previously healthy patient with recent influenza more likely has CA-MRSA. (Choice B) Histoplasma pulmonary infections usually present with mild, subacute symptoms, including fever, myalgias, cough, and chest pain. Focal pulmonary infiltrates are common and may be mistaken for bacterial community-acquired pneumonia. This patient with acute, severe symptoms after influenza more likely has CA-MRSA. (Choice C) Klebsiella is an organism most commonly associated with nosocomial pneumonia, but it may occasionally cause community-acquired pneumonia in patients who have diabetes mellitus or who abuse alcohol. Klebsiella is not a common influenza-related pathogen. (Choice D) Legionella is a common cause of community-acquired pneumonia and usually manifests with high fever and gastrointestinal symptoms prior to pulmonary symptoms. This patient with no gastrointestinal symptoms, recent influenza, and multilobar cavitary infiltrates is more likely to have CA-MRSA. (Choice E) Peptostreptococcus is an anaerobic bacterium that may rarely cause pulmonary infection with putrid sputum and abscess/empyema. This organism is not a common influenza-related pathogen. (Choice F) Pneumocystis pneumonia occurs primarily in patients with HIV (CD4 <200/mm³) or those who are severely immunocompromised (eg, post-transplantation). Manifestations in patients without HIV often include fever, dry cough, and fulminant respiratory failure. (Choice H) Streptococcus pneumoniae is the most common cause of influenza-related bacterial pneumonia but is rare in young individuals and less likely to cause cavitary lung lesions. Educational objective: Secondary bacterial pneumonia is the most common influenza complication and should be suspected when fever and pulmonary symptoms worsen after initial improvement. Most cases occur in patients age >65, but community-acquired methicillin-resistant Staphylococcus aureus has a predilection for young patients with recent influenza. This pathogen causes rapidly progressive, necrotizing pneumonia with high fever, productive cough (often with hemoptysis), leukopenia, and multilobar cavitary infiltrates.

A 19-Year-Old Man Is Brought to the Emergency Department by His