A 30-year-old man is admitted to the intensive care unit after his wife found him unconscious at home. She says that he has lost a significant amount of weight recently despite no significant change in dietary habits. Laboratory studies show a serum pH of 7.1 and positive serum ketones. His mucus membranes are extremely dry. Treatment is initiated, and the patient's condition improves. However, he now has fever, headache, and eye pain. Examination of the nasal cavity shows a black necrotic eschar adherent to the inferior turbinate. Which of the following procedures would most likely reveal the pathogen responsible for this patient's infection?

Question

A 30-year-old man is admitted to the intensive care unit after his wife found him unconscious at home.  She says that he has lost a significant amount of weight recently despite no significant change in dietary habits.  Laboratory studies show a serum pH of 7.1 and positive serum ketones.  His mucus membranes are extremely dry.  Treatment is initiated, and the patient's condition improves.  However, he now has fever, headache, and eye pain.  Examination of the nasal cavity shows a black necrotic eschar adherent to the inferior turbinate.  Which of the following procedures would most likely reveal the pathogen responsible for this patient's infection?

Quizplus · Accepted Answer

Facial pain, headache, and nasal eschar in a patient with likely diabetic ketoacidosis (pH 7.1, positive ketones, and dry mucous membranes in a young patient with recent unintended weight loss) are highly suggestive of mucormycosis, caused by Mucor or Rhizopus, among others. Most cases are rhinocerebral; the infection (acquired by spore inhalation) ascends from the nasal passage to the sinuses/orbits and then sometimes to the brain, leading to confusion, neurological deficits, and death. The increased incidence of mucormycosis in patients with diabetes mellitus is due to the ketone reductase activity of Rhizopus, allowing it to thrive in ketoacidotic environments. Histologic examination (eg, mucosal biopsy) is necessary for diagnosis. The fungi appear as ribbon-like broad nonseptate hyphae with right-angle branching. Tissue invasion is seen along blood vessels; vascular thrombosis and tissue necrosis can occur. A black necrotic eschar in the nasal cavity is characteristic. Management includes amphotericin B and surgical debridement. Mucormycosis (common in diabetes) must be differentiated from invasive aspergillosis causing rhinosinusitis (common in neutropenic patients). On light microscopy, Aspergillus is seen as septated narrow hyphae with sharp-angle branching. (Choice A) Blood cultures are usually negative in mucormycosis despite the organism's angioinvasive nature. In contrast, blood cultures can be useful in diagnosing candidemia, which has a variable clinical presentation ranging from low-grade fever to severe sepsis with multiorgan failure. (Choice B) Lumbar puncture helps to diagnose cryptococcal meningitis, a fungal infection that typically has an indolent presentation and usually affects patients with AIDS. India ink staining of cerebrospinal fluid reveals the classic encapsulated yeast of Cryptococcus neoformans. (Choice D) Ophthalmoscopy is useful for the diagnosis of Candida endophthalmitis, which typically presents with impaired visual acuity. (Choices E and F) Serologic testing is important in the diagnosis of allergic bronchopulmonary aspergillosis (ABPA), where increased titers of IgE and antibodies to Aspergillus fumigatus are seen. Skin hypersensitivity testing is also useful. However, the typical presentation of ABPA is recurrent episodes of fever and bronchial obstruction in a patient with asthma. Educational objective: Facial pain, headache, and a black necrotic eschar in the nasal cavity of a patient with diabetic ketoacidosis are highly suggestive of mucormycosis. Histologic examination of the affected tissue is necessary to confirm the diagnosis. The fungi show broad nonseptate hyphae with right-angle branching. Treatment consists of surgical debridement and antifungal therapy. __________ References: Novel perspectives on mucormycosis: pathophysiology, presentation, and management. (http://www.ncbi.nlm.nih.gov/pubmed/16020690)

A 30-Year-Old Man Is Admitted to the Intensive Care Unit