WBR0188
| 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 65-year old woman, formerly a migrant worker, living in Southwestern US is brought to the hospital with complaints of chest pain, shortness of breath, body aches, especially of the knees and ankles and fatigue. She has been a smoker all her life but is in good health with no other diseases except for Osteoarthritis. A serological test is negative for any significant bacterial antibodies. She is found to have an erythematous skin rash in her lower limbs. A chest radiograph reveals several calcifying lesions. Which of the following structures is most likely to be seen on microscopic examination of 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 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.
 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. |
| Approved | Approved::No |
| Keyword | WBRKeyword::Microbiology, WBRKeyword::Eukaryotes, WBRKeyword::Yeast, WBRKeyword::Coccidioidomycosis, WBRKeyword::C immitis, WBRKeyword::Coccidioides immitis, WBRKeyword::Valley fever |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |