A 64-year-old man is evaluated for worsening cough and shortness of breath. The patient has a history of hypertension and type 2 diabetes mellitus. He smokes a pack of cigarettes daily and drinks alcohol occasionally. Temperature is 38 C (100.4 F), blood pressure is 140/82 mm Hg, and pulse is 92/min. Lung auscultation reveals abnormal breath sounds. Chest x-ray is shown below. Which of the following is the most likely cause of the observed pulmonary findings in this patient?

Question

A 64-year-old man is evaluated for worsening cough and shortness of breath.  The patient has a history of hypertension and type 2 diabetes mellitus.  He smokes a pack of cigarettes daily and drinks alcohol occasionally.  Temperature is 38 C (100.4 F), blood pressure is 140/82 mm Hg, and pulse is 92/min.  Lung auscultation reveals abnormal breath sounds.  Chest x-ray is shown below.  Which of the following is the most likely cause of the observed pulmonary findings in this patient?

Quizplus · Accepted Answer

11ec160b_3a09_4504_9249_5fdad086a703_MD0001_00 This patient has cough, shortness of breath, fever, and a right lower lobe infiltrate on chest x-ray, indicating lobar pneumonia likely due to a community-acquired pathogen (eg, Streptococcus pneumoniae). Lobar pneumonia is characterized by a step-wise inflammatory response, as follows: Congestion (day 0-2) - Neutrophils respond to bacterial components (eg, peptidoglycan) by releasing cytokines that increase the permeability of the pulmonary capillary endothelium, which allows circulating immune cells to more easily migrate to the area. Increased capillary permeability also leads to the accumulation of erythrocytes and abundant proteinaceous fluid in the alveolar space, resulting in the affected lobe becoming heavy and red. Red hepatization (day 2-4) - The proteinaceous fluid transforms into fibrin strands, resulting in a confluent exudate of fibrin, neutrophils, and erythrocytes. On gross examination, the lobe appears liver-like: Red, firm, and airless. Gray hepatization (day 4-7) - Red cell disintegration along with increased leukocyte infiltration causes the lung to appear gray rather than red. Neutrophils begin to be replaced by macrophages that begin the repair process. Resolution (>7 days) - Macrophages secrete digestive enzymes that liquefy the fibrinous exudate, which is reabsorbed, expectorated, or phagocytized by macrophages. The lung parenchyma regains its normal appearance by approximately 3 weeks. Besides lobar pneumonia, there are 2 other major morphologic categories of pneumonia. Bronchopneumonia is an infection of the terminal bronchioles that results in patchy consolidation of a number of lobules. Interstitial pneumonia is an infection of the interstitial tissue of the lung with minimal or no alveolar infiltrate; atypical pneumonias (eg, Mycoplasma pneumoniae, Chlamydia pneumoniae) are often associated with an interstitial infiltrate. (Choice A) Cardiogenic pulmonary edema is characterized by the accumulation of fluid in the alveoli due to elevations in hydrostatic pressure within the pulmonary capillaries. Examination often reveals bibasilar crackles and chest x-ray typically shows perihilar alveolar edema with cephalization of the pulmonary vessels. (Choice B) Asthma is characterized by smooth muscle inflammation of the airways leading to intermittent bronchoconstriction and airflow obstruction. Although cough and shortness of breath can occur during asthma exacerbations, fever and a lobar infiltrate are not typical. (Choice C) Idiopathic pulmonary fibrosis is associated with pulmonary fibroblast proliferation and extracellular matrix deposition leading to progressive destruction of the pulmonary architecture. Patients typically present with slowly worsening dyspnea, nonproductive cough, and bilateral "Velcro"-sounding crackles. Fever is uncommon and chest x-ray usually reveals increased reticular (interstitial) markings. (Choice E) Chronic bronchitis is associated with goblet cell metaplasia and inflammation in the large airways. The hypersecretion of mucous can lead to chronic productive cough, dyspnea, and wheezes on examination. Lobar infiltrate is uncommon as the alveoli are not primarily affected. Educational objective: Lobar pneumonia is marked by the cytokine-mediated accumulation of neutrophils and proteinaceous material in the alveoli. Over several days, the proteinaceous material becomes fibrinous, neutrophils are replaced by macrophages, and macrophages digest the fibrinous exudate, thereby restoring normal lung histology. __________ References: Pathophysiology of community acquired pneumonia. (http://www.ncbi.nlm.nih.gov/pubmed/23155817) Conceptual approaches to lung injury and repair. (http://www.ncbi.nlm.nih.gov/pubmed/25830855)

A 64-Year-Old Man Is Evaluated for Worsening Cough and Shortness