WBR0188

Author	[[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1] (Reviewed by Will Gibson)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology
Sub Category	SubCategory::Infectious Disease
Prompt	[[Prompt::A 65-year old woman presents to urgent care for fatigue, myalgias, cough and fever. She reports a forty year smoking history, but has no otherwise remarkable past medical history. She emigrated from Mexico as a teenager and has been a migrant worker in southern california since. Three weeks ago, her home was destroyed in an earthquake and she has been living with her son. Physical exam reveals an erythematous rash on the lower limbs (pictured below). A chest radiograph reveals multiple nodules and hilar adenopathy. Which of the following is most likely to be seen on microscopic examination of a lung tissue biopsy? ]]
Answer A	AnswerA::Broad based budding yeast
Answer A Explanation	AnswerAExp::Broad based budding yeast is seen in Blastomyces dermatitidis.
Answer B	AnswerB::Spherules with endospores
Answer B Explanation	AnswerBExp::Spherules with endospores characteristically describes Coccidioides immitis.
Answer C	AnswerC::Septate hyphae branching dichotomously at acute angles
Answer C Explanation	AnswerCExp::Septate hyphae branching dichotomously at acute angles describes Aspergillus fumigatus.
Answer D	AnswerD::Non septate hyphae with broad angles
Answer D Explanation	AnswerDExp::Non septate hyphae with broad angles describes Mucor species.
Answer E	AnswerE::Monomorphic encapsulated yeast
Answer E Explanation	AnswerEExp::Monomorphic encapsulated yeast describes Cryptococcus neoformans.
Right Answer	RightAnswer::B
Explanation	[[Explanation::The patient in this vignette has developed symptoms of systemic coccidiomycosis. While her symptoms and imaging studies are non-specific, several factors make Coccidiodes the most likely etiologic agent: The patient comes from the southwestern United States, an endemic area of coccidiodes. The causative organism in this case is coccidioides immitis. The diagnostic clues here are southwest U.S., migrant worker, erythematous skin rash and the multiple calcifying lesions.The diagnostic form in tissue is a spherule with endospores (pictured below). Although lesions in histoplasma capsulatum infection have a tendency to calcify as they heal, it does not form the characteristic spherule seen in coccidioides immitis. <img src="http://static.wikidoc.org/3/38/WJGSystemicMycosesDist2.svg" width="400"> Histopathology of coccidioidomycosis. Spherule of Coccidioides immitis with endospores. Calcofluor stain. From Public Health Image Gallery Educational Objective: Coccidioides immitis is a pathogenic fungus endemic to the Southwestern U.S that causes pulmonary disease and appears microscopically as spherules with endospores. References: First Aid 2014 page 146]]
Approved	Approved::Yes
Keyword	WBRKeyword::Microbiology, WBRKeyword::Eukaryotes, WBRKeyword::Yeast, WBRKeyword::Coccidioidomycosis, WBRKeyword::C immitis, WBRKeyword::Coccidioides immitis, WBRKeyword::Valley fever
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