A 16-year-old previously healthy adolescent developed nonproductive cough, dyspnea, and wheezing after traveling abroad. The patient has no history of allergies and has had no recent upper respiratory illness. The symptoms spontaneously resolved after several days, but soon after, she began having abdominal discomfort, anorexia, and nausea. Stool microscopy results are shown in the following image: Which of the following was the most likely cause of this patient's pulmonary symptoms?

Question

A 16-year-old previously healthy adolescent developed nonproductive cough, dyspnea, and wheezing after traveling abroad.  The patient has no history of allergies and has had no recent upper respiratory illness.  The symptoms spontaneously resolved after several days, but soon after, she began having abdominal discomfort, anorexia, and nausea.  Stool microscopy results are shown in the following image:  Which of the following was the most likely cause of this patient's pulmonary symptoms?

Quizplus · Accepted Answer

This patient's recent travel, transient pulmonary symptoms, and subsequent gastrointestinal manifestations are suspicious for a parasitic infection involving the lungs and intestines. Stool microscopy reveals an oval egg with a thick outer shell and a single interior ovum, thereby confirming Ascaris lumbricoides (roundworm) infection. A lumbricoides is a common parasitic infection in Asia, Africa, and South America. Most cases in the United States arise in travelers to these regions. Transmission occurs when eggs are ingested via contaminated food or water. Eggs hatch into larvae in the small intestine, penetrate the intestinal wall, and migrate to the alveoli, where they mature. Pulmonary infection is generally asymptomatic, but a minority of infected individuals develop Loeffler syndrome, a transient, eosinophilic pneumonitis with pulmonary symptoms (eg, dry cough, dyspnea, wheezing). After several days, larvae are coughed out of the alveoli and subsequently swallowed into the gastrointestinal tract, where they mature into long (25- to 35-cm) adult worms that shed up to 200,000 eggs per day. Most gastrointestinal infections are asymptomatic, but some patients have abdominal discomfort, nausea/vomiting, and diarrhea. The diagnosis of gastrointestinal tract infection is made by inspecting the stool for eggs; treatment with antiparasitic drugs (eg, albendazole) is generally curative. (Choice A) Rheumatic fever is associated with the formation of cross-reacting antibodies to renal, neuronal, and cardiac antigens following group A Streptococcus pharyngitis. Eggs would not be seen in stool. (Choice B) Hypersensitivity pneumonitis, an immune reaction to an inhaled agent, can occur following exposure to mold dust or spores. Patients generally develop acute fever, nausea, cough, and dyspnea. However, wheezing is uncommon, and eggs would not be shed in stool. (Choice C) Chagas disease, a parasitic infection caused by Trypanosoma cruzi, can cause myopericarditis during acute infection. However, cardiac and gastrointestinal manifestations are much more likely to occur years or decades later. In addition, T cruzi is not shed in stool; it can sometimes be visualized on blood smear. (Choice E) Type IV hypersensitivity reactions are mediated by T cells and are often seen as part of certain drug reactions (eg, Stevens-Johnson syndrome). In contrast, Ascaris infections are associated with IgE-mediated (eosinophilic) hypersensitivity. Educational objective: Ascaris lumbricoides is transmitted via contaminated food or water. Eggs hatch into larvae in the small intestine, penetrate the intestinal wall, and migrate across the lung into the alveoli. Larvae are subsequently coughed up and swallowed into the gastrointestinal tract, where they mature to adult worms. Most patients are asymptomatic, but some develop early pulmonary manifestations (Loeffler syndrome) or later gastrointestinal symptoms.

A 16-Year-Old Previously Healthy Adolescent Developed Nonproductive Cough, Dyspnea, and Wheezing