Mucomycosis

CASE 1

• A 45 year old woman with type 1 diabetes mellitus (on insulin) is admitted for pain and bulging of the left eye. She has recently run out of insulin and began giving herself half of her normal dose.

• On admission, She is febrile to 38.4 and her respiratory rate is increased to 30/min. Urine shows 4+ glucose and 4+ ketones on the dipstick. A blood glucose is 15.3 mmol/L, and her electrolytes show a large anion gap, suggesting metabolic acidosis. A diagnosis of diabetic ketoacidosis is made, and the patient is treated with intravenous fluids and insulin.

• A CT scan of the head (below) shows opacity of both maxillary sinuses with erosion of the medial and anterior walls of the sinus on the left (arrows). Compare the right side with the left and note the bulging of the soft tissue on the left side (behind the arrows), the area immediately beneath the affected eye.

• The patient is treated with amphotericin B and taken urgently to the operating room to debride the sinuses and to remove all infected tissues, including the entire left orbit. Sections of the tissues removed are stained for fungi, and they show infiltration of the tissue with non-spetate hyphae that branch at right angles. A culture grows Rhizopus oryzae, a zygomycetes and member of the Family Mucorales.

Questions:

1. What conditions are necessary for this common fungus to grow in this patient's sinuses and invade the bone? Consider the role of the blood glucose and the acidosis?
2. What is the likelihood that this patient will survive this episode?
3. If the infection recurs after surgery, where will the fungus likely invade next?
4. Why is antifungal therapy alone typically inadequate to treat this infection?
5. Are there other patients, besides those with diabetic ketoacidosis who are at risk of acquiring this rare infection?