Kaplan USMLE Step 2: Patient with diabetes has sudden loss of vision

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 2 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.

An 85-year-old woman develops bilateral orbital and facial pain, headache and sudden loss of vision in the right eye, all of which developed over the course of 2 days. She has a history of diabetes and is on dialysis for chronic renal failure. Her right eyelid is red and swollen. She also has a complete loss of vision and movement of the right eye, as well as partial loss of vision of the left eye.

The mucosa of the nasal passages is swollen and necrotic with black discoloration. MRI scan of the head shows soft-tissue swelling of the nasal mucosa, sinuses and orbital tissues, with no evidence of cavernous sinus thrombosis or retro-orbital cellulitis. A biopsy specimen of the nasal and sinus mucosa shows thrombosed vessels and multiple broad, nonseptate hyphae with right-angle branches.

Which of the following is the most appropriate next step in management?

A. Amphotericin B and surgical debridement

B. Corticosteroids

C. Craniotomy with orbital decompression

D. Fluconazole

E. Urgent sinus decompression

The correct answer is A.

Rhino-orbital-cerebral mucormycosis is a rapidly progressive and devastating invasive fungal infection that can present with orbital swelling and necrotic nasal mucosa. It urgently requires both source control and aggressive, systemic antifungal medical treatment. This is accomplished via surgical debridement and amphotericin B.

Choice B. High-dose corticosteroids would be the correct treatment for an autoimmune process such as giant-cell temporal arteritis, but it is not indicated here. In fact, steroids may worsen the disease process by suppressing immunity and promoting hyperglycemia.