A 45-year-old man comes to the emergency department due to several days of cough and fever. His temperature is 38.4 C (101.2 F), blood pressure is 117/76 mm Hg, pulse is 92/min, and respirations are 18/min. Physical examination of the right lung reveals occasional rales and decreased breath sounds at the base. A chest x-ray demonstrates a lung infiltrate, hilar adenopathy, and a right-sided pleural effusion. Lung tissue obtained from the patient reveals the findings in the image below: Which of the following is the most likely cause of this patient's condition?

Question

A 45-year-old man comes to the emergency department due to several days of cough and fever.  His temperature is 38.4 C (101.2 F), blood pressure is 117/76 mm Hg, pulse is 92/min, and respirations are 18/min.  Physical examination of the right lung reveals occasional rales and decreased breath sounds at the base.  A chest x-ray demonstrates a lung infiltrate, hilar adenopathy, and a right-sided pleural effusion.  Lung tissue obtained from the patient reveals the findings in the image below:  Which of the following is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

11ec160b_3890_39ff_9249_dbb51eebf4d4_MD0001_00 Coccidioides immitis is a dimorphic fungus that is endemic to the desert areas of the United States and Mexico. It can cause lung disease in immunocompetent patients and disseminated disease in the immunocompromised. Coccidioides exists in the environment in the form of mold (hyphae); in humans, microscopic examination of affected tissues shows thick-walled spherules packed with endospores. As seen in the image above, some spherules may be rupturing and others may be empty. The spherules are larger than surrounding red blood cells (RBCs). Culture on Sabouraud agar and serology are also important in making the diagnosis. (Choice A) Aspergillus fumigatus commonly causes pulmonary disease in immunocompromised patients. It has a mold form only. Aspergillus have septate hyphae that branch at 45-degree angles. (Choice B) The characteristic appearance of Blastomyces dermatitidis is that of a round yeast with broad-based budding. These yeasts have thick, doubly refractive walls. (Choice D) Cryptococcus neoformans is a yeast with a thick capsule. When tissue specimens infected with C neoformans are stained with India ink, the capsule does not absorb the ink, resulting in a clear halo. The most common manifestation of C neoformans infection is meningitis, particularly among immunocompromised patients. (Choice E) Cytomegalovirus can cause pneumonia in transplant patients. Prominent intranuclear inclusions surrounded by a clear halo are virtually pathognomonic for pulmonary cytomegalovirus. (Choice F) Histoplasma capsulatum would appear histopathologically as small oval yeast forms within macrophages; unlike the spherules of Coccidioides, Histoplasma yeast forms are smaller than surrounding RBCs. (Choice G) Rhizopus species typically cause rhino-orbito-cerebral mucormycosis but can cause lung disease in immunocompromised patients. The species has only a mold form, with broad ribbonlike hyphae with rare septations. (Choice H) The pustular and ulcerated lesions of sporotrichosis (caused by the fungus Sporothrix schenckii and typically acquired by direct skin inoculation [eg, scrapes from rose bushes]) are localized to the site of the wound or associated lymphatic channels. On histologic examination, cigar-shaped yeast may be seen. Educational objective: Coccidioides immitis infection can be asymptomatic or it can cause pulmonary disease ranging from a flulike illness to chronic pneumonia. It causes disseminated disease in immunocompromised patients. Spherules containing endospores are found in tissue samples.

A 45-Year-Old Man Comes to the Emergency Department Due to Several