WBR0187
| Author | [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1], Serge Korjian M.D. (Reviewed by Serge Korjian)]] |
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| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Microbiology |
| Sub Category | SubCategory::Infectious Disease |
| Prompt | [[Prompt::A 42-year-old man with history significant for poorly controlled diabetes mellitus presents to the emergency department with a 2-day history of fever, headache, and facial swelling. Following extensive work-up, a nasal biopsy frozen section reveals a non-septate irregular width hyphae branching at 90-degree angles. What is the likely causative agent of this patient’s condition?]] |
| Answer A | AnswerA::Candida albicans |
| Answer A Explanation | AnswerAExp::Candida albicans forms pseudohyphae and true hyphae at 37 degree Celsius in serum with the germ tube test. |
| Answer B | AnswerB::Aspergillus fumigatus |
| Answer B Explanation | AnswerBExp::Aspergillus fumigatus is a monomorphic filamentous fungus, dichotomously branching septate hyphae at 45 degrees angle. |
| Answer C | AnswerC::Blastomyces dermatitidis |
| Answer C Explanation | AnswerCExp::Blastomyces dermatitidis forms hyphae with nondescript conidia. The tissue form is a broad-based budding yeast. |
| Answer D | AnswerD::Rhizopus |
| Answer D Explanation | AnswerDExp::Rhizopus forms broad ribbon-like nonseptate hyphae branching at 90-degree angles. |
| Answer E | AnswerE::Sporothrix schenckii |
| Answer E Explanation | AnswerEExp::Sporothrix schenckii is a dimorphic fungus that forms cigar-shaped yeast in tissue. |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::This is a case of zygomycosis aka mucormycosis or phycomycosis, caused by Rhizopus. Other fungal organisms that can cause this infection are Mucor and Absidia. It may arise as a complication in diabetic ketoacidosis or in leukemic patients and it typically presents as a rhinocerebral disease characterized by paranasal swelling, necrotic tissues, hemorrhagic exudates from the nose and eyes and confusion. On tissue biopsy, it shows as broad ribbon-like nonseptate hyphae branching at 90-degree angles.
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| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
