WBR0189
| Author | [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Microbiology |
| Sub Category | SubCategory::Infectious Disease |
| Prompt | [[Prompt::A 45-year old HIV positive woman presents to the emergency department with complaints of headache, cough, shortness of breath and blurred vision. Physical examination reveals lymphadenopathy, tachypnea, rales and papilledema. A CT scan of the head is normal but CSF examination reveals encapsulated organisms that stain with India ink. Which of the following correctly describes the causative agent?]] |
| Answer A | AnswerA::Dimorphic encapsulated yeast |
| Answer A Explanation | AnswerAExp::The only encapsulated fungal pathogen is Cryptococcus neoformans and it is monomorphic, not dimorphic. |
| Answer B | AnswerB::Monomorphic encapsulated yeast |
| Answer B Explanation | AnswerBExp::Monomorphic encapsulated yeast describes Cryptococcus neoformans, which is the causative agent in this vignette. |
| Answer C | AnswerC::Yeast with broad based budding |
| Answer C Explanation | [[AnswerCExp::Broad based budding yeast describes Blastomyces dermatitidis. Blastomyces is the rarest of the systemic mycoses and casuses chronic inflammatory lung disease. It is endemic to the Mississippi river valley, but is not a common cause of meningitis in HIV-positive patients.]] |
| Answer D | AnswerD::Consists of branching septate hyphae |
| Answer D Explanation | AnswerDExp::Aspergillus fumigatus consists of branching septate hyphae. Aspergillus is not a common cause of meningitis in HIV-positive patients. |
| Answer E | AnswerE::Spaghetti and meatballs appearance on KOH stain |
| Answer E Explanation | [[AnswerEExp::Spaghetti and meatballs on KOH stain describes Malassezia furfur, the causative agent of tinea versicolor.]] |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::The patient in this vignette has Cryptococcosis, caused by cryptococcus neoformans.
The clues in this vignette are HIV, headache, blurred vision, encapsulated organism in CSF and the India ink stain. Also note that Cryptococcus neoformans is monomorphic. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Cryptococcus, WBRKeyword::Cryptococcus neoformans, WBRKeyword::HIV, WBRKeyword::Opportunistic infection, WBRKeyword::Fungus, WBRKeyword::Yeast |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |