WBR0203

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology
Sub Category	SubCategory::Infectious Disease
Prompt	[[Prompt::A 37-year-old diabetic man presents to the emergency department (ED) with severe headache and eye pain. His wife explains that he has been hospitalized a few weeks ago for diabetic ketoacidosis. She states that the patient's past medical history is significant for type 1 diabetes mellitus diagnosed at the age of 23 years; and the patient has recently been non-compliant with his insulin injections. In the ED, initial work-up is remarkable for elevated glucose levels in the urine and serum. Examination of the nasal cavity reveals a black necrotic eschar. Neurological exam is remarkable for facial palsy and ophthalmoplegia. What are the microscopic characteristics of the organism responsible for this patient's condition?]]
Answer A	AnswerA::Pseudohyphae and budding yeasts
Answer A Explanation	[[AnswerAExp::Presence of pseudohyphae is a feature of Candida spp. when observed at 20 °C. In contrast, Candida albicans may appear as germ tubes at 37 °C.]]
Answer B	AnswerB::Broad, aseptate, hyphae with wide-angled branching
Answer B Explanation	AnswerBExp::Broad non-septate hyphae with wide-angled branching is a feature of mucormycotina, which are responsible for mucormycosis
Answer C	AnswerC::Septate hyphae with V-shaped branching
Answer C Explanation	AnswerCExp::Septate hyphae with V-shaped branching is a feature of ''Aspergillus fumigatus'' infections.
Answer D	AnswerD::Oval yeast cells within macrophages
Answer D Explanation	AnswerDExp::Oval yeast cells within macrophages are a feature of ''Histoplasma capsulatum''
Answer E	AnswerE::Broad-based budding
Answer E Explanation	AnswerEExp::Broad-based budding is a feature seen of ''Blastomyces dermatitidis''
Right Answer	RightAnswer::B
Explanation	[[Explanation::Mucormycotina are irregular, large, aseptate, hyphae that look like ribbons with wide-angled branching. They are responsible for the opportunistic fungal infection, mucormycosis. Mucormycosis is a severe necrotic infection that is characterized by vascular infiltration and thrombosis. It commonly affects patients with long-standing diabetes mellitus or those with neutropenia and immunosuppression. The disease has many forms, the most common of which is the rhinocerebral form. Other forms include the pulmonary, cutaneous, gastrointestinal, and disseminated forms. Clinical manifestations depend on the disease form. Rhino-orbital-cerebral mucormycosis presents with headache, rhinosinusitis, and eschar in the nasal cavity. It may penetrate the cribriform plate in advanced disease and result in CNV or CVII palsy, epidural/subdural abscesses, frontal lobe abscesses (soap bubble appearance on CT scan), cavernous sinus thrombosis, ophthalmoplegia, and loss of vision. On the other hand, pulmonary mucormycosis often presents with high-grade fever, hemoptysis, and symptoms of pneumonia with a characteristic "reverse halo" radiographic sign that suggests early disease. Risk factors for the development of mucormycosis include neutropenia, hyperglycemia, iron overload, high-dose steroid therapy, renal failure, exposure to voriconazole or caspofungin, and malnutrition. Various patient populations are predisposed to different forms of the disease. Diabetic patients are more likely to develop the rhinocerebral form, immunosuppressed transplant recipients are more likely to develop the pulmonary form, and IV drug users are more likely to develop the cerebral form. It is thought that the development of mucormycosis infection among diabetics is associated with the combination of hyperglycemia, ketosis, and acidosis. All 3 factors increase the availability of free iron that the fungus needs for growth. Management is aimed at reversal of risk factors, systemic antifungal therapy with amphotericin B, and surgical debridement. Educational Objective: Mucormycotina are irregular, large, aseptate, hyphae that look like ribbons with wide-angled branching. They are responsible for the opportunistic fungal infection, mucormycosis. Mucormycosis is a severe necrotic infection that is characterized by vascular infiltration and thrombosis. It commonly affects patients with long-standing diabetes mellitus or those with neutropenia and immunosuppression. References: Sun H, Singh N. Mucormycosis: its contemporary face and management. Lancet Infect Dis. 2011;11:301-11. First Aid 2014 page 148]]
Approved	Approved::No
Keyword	WBRKeyword::Diabetic ketoacidosis, WBRKeyword::Mucormycosis, WBRKeyword::Diabetes, WBRKeyword::Ketoacidosis, WBRKeyword::Mucormycotina, WBRKeyword::Eschar, WBRKeyword::Fungal infection, WBRKeyword::Fungi, WBRKeyword::Opportunistic infection, WBRKeyword::Amphotericin B, WBRKeyword::Cribriform plate, WBRKeyword::Rhinocerebral mucormycosis
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