A 44-year-old man comes to the emergency department with a 3-day history of fever, chills, malaise, dyspnea, and a cough productive of "greenish" sputum. The patient has no prior medical problems and has never been hospitalized. He has a 25-pack-year smoking history and drinks 4-5 beers a week. His temperature is 39.4 C (103 F), blood pressure is 130/80 mm Hg, pulse is 98/min, and respirations are 20/min. On examination, dullness to percussion, crackles, and egophony are present at the right lung base. The remainder of the examination is normal. Chest x-ray shows a dense infiltrate occupying the entire right lower lobe. Which of the following most likely accounts for the color of this patient's sputum?

Question

A 44-year-old man comes to the emergency department with a 3-day history of fever, chills, malaise, dyspnea, and a cough productive of "greenish" sputum.  The patient has no prior medical problems and has never been hospitalized.  He has a 25-pack-year smoking history and drinks 4-5 beers a week.  His temperature is 39.4 C (103 F), blood pressure is 130/80 mm Hg, pulse is 98/min, and respirations are 20/min.  On examination, dullness to percussion, crackles, and egophony are present at the right lung base.  The remainder of the examination is normal.  Chest x-ray shows a dense infiltrate occupying the entire right lower lobe.  Which of the following most likely accounts for the color of this patient's sputum?

Quizplus · Accepted Answer

This middle-aged man presenting with new-onset fevers, productive cough, and a dense lobar infiltrate likely has community-acquired pneumonia (CAP). CAP in otherwise healthy individuals is most commonly caused by Streptococcus pneumoniae, the most common bacterial etiology worldwide. Tobacco use further increases its risk. In nonelderly patients, pneumococcal pneumonia presents with abrupt-onset fevers, rigors, tachypnea, and productive cough with consolidation in one lobe of the lungs. Neutrophil myeloperoxidase is responsible for the green color of pus and sputum in bacterial infections. It is a blue-green heme-based pigmented molecule contained within the azurophilic granules of neutrophils and catalyzes the production of hypochlorous acid from chloride and hydrogen peroxide during the phagocytic respiratory burst. (Choices A and B) Both the "currant jelly" sputum seen in pneumonia caused by Klebsiella pneumoniae and the "rusty" color occasionally seen in pneumococcal pneumonia are due to extravasation of red blood cells and hemoglobin into the sputum caused by extensive inflammation and necrosis. (Choice C) Pseudomonas pneumonia can cause a blue-green pigment due to the production of pyocyanin, but Pseudomonas is not a common cause of CAP in otherwise healthy adults. (Choice D) Respiratory epithelium sloughing and mucopolysaccharide production can contribute to the formation of sputum in patients with respiratory infection but does not contribute to sputum's green color. Educational objective: The green discoloration of pus or sputum seen during common bacterial infections is due to the presence of myeloperoxidase, a blue-green heme-based enzyme that is released from neutrophil azurophilic granules and forms hypochlorous acid (bleach). __________ References: Myeloperoxidase in human neutrophil host defence. (http://www.ncbi.nlm.nih.gov/pubmed/24844117)

A 44-Year-Old Man Comes to the Emergency Department with a 3-Day