WBR0188: Difference between revisions

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|MainCategory=Microbiology
|MainCategory=Microbiology
|SubCategory=Infectious Disease
|SubCategory=Infectious Disease
|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?
|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?
 
[[File:WBR0188prompt.jpg]]
|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.
|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.
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|AnswerE=Monomorphic encapsulated yeast
|AnswerE=Monomorphic encapsulated yeast
|AnswerEExp=Monomorphic encapsulated yeast describes Cryptococcus neoformans.
|AnswerEExp=Monomorphic encapsulated yeast describes Cryptococcus neoformans.
|EducationalObjectives=Coccidioides immitis is a pathogenic fungus endemic to the Southwestern U.S, that causes pulmonary disease and appears microscopically as spherules with endospores.
|EducationalObjectives=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
|References=First Aid 2014 page 146
|RightAnswer=B
|RightAnswer=B
|WBRKeyword=Microbiology, Eukaryotes, Yeast, Coccidioidomycosis, C immitis, Coccidioides immitis, Valley fever,
|WBRKeyword=Microbiology, Eukaryotes, Yeast, Coccidioidomycosis, C immitis, Coccidioides immitis, Valley fever,
|Approved=No
|Approved=Yes
}}
}}

Revision as of 03:28, 1 November 2014
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 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 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.


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
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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