A 48-year-old man is evaluated for shortness of breath and dry cough for 1 week. The patient has never had similar symptoms in the past and takes no medications. He has a 5-pack-year smoking history and does not use alcohol or illicit drugs. The patient is a pig farmer in Ohio and has not traveled recently. Temperature is 37.8 C (100 F), blood pressure is 128/85 mm Hg, pulse is 95/min, and respirations are 16/min. Lung auscultation reveals scattered wheezing and crackles. Peripheral blood smear is shown below. The nucleated cells seen on this patient's peripheral smear most likely perform which of the following functions?

Question

A 48-year-old man is evaluated for shortness of breath and dry cough for 1 week.  The patient has never had similar symptoms in the past and takes no medications.  He has a 5-pack-year smoking history and does not use alcohol or illicit drugs.  The patient is a pig farmer in Ohio and has not traveled recently.  Temperature is 37.8 C (100 F), blood pressure is 128/85 mm Hg, pulse is 95/min, and respirations are 16/min.  Lung auscultation reveals scattered wheezing and crackles.  Peripheral blood smear is shown below.  The nucleated cells seen on this patient's peripheral smear most likely perform which of the following functions?

Quizplus · Accepted Answer

This patient's presentation is concerning for Loeffler syndrome, a transient eosinophilic pneumonitis (eg, dry cough, dyspnea, wheezing) caused by migration of parasitic roundworm larva (eg, Ascaris suum from pigs) through the lungs. His peripheral smear shows numerous erythrocytes and a few scattered platelets accompanied by 2 larger cells with bilobed nuclei and eosinophilic granules; the 2 larger cells are eosinophils. Eosinophils play a prominent role in allergic disease (eg, asthma, drug reactions) and in defense against parasitic infection. Major basic protein is the predominant substance contained within eosinophilic granules, and it acts as a potent toxin against helminths (parasitic worms). Release of major basic protein by eosinophils causes damage to epithelial and endothelial cells and is a major mechanism of chronic lung damage in certain pulmonary conditions (eg, asthma, Ascaris infection). (Choice A) Plasma cells produce antibodies that opsonize bacteria to facilitate phagocytosis. (Choice C) Pattern recognition receptors (eg, dectin-1) on phagocytic cells allow for detection and destruction of fungi by the innate immune system. (Choice D) Virus-infected cells typically lack MHC class I proteins on their surface; these cells are identified and killed by natural killer cells. (Choice E) Macrophages secrete transforming growth factor-beta (TGF-β), which stimulates fibroblasts to release collagen and form scar tissue. Educational objective: Eosinophils have bilobed nuclei and numerous eosinophilic granules in the cytoplasm and are important in allergic disease and defense against parasitic infection. The eosinophilic granules predominantly contain major basic protein, which acts as a potent antihelminthic toxin. Major basic protein also damages epithelial and endothelial cells and is a major cause of chronic lung damage in asthma.

A 48-Year-Old Man Is Evaluated for Shortness of Breath and Dry