In medicine, clinicians are constantly reminded to look for the horses, not the zebras. While that remains good advice, especially to those just beginning their careers, a mind that is open to the unusual remains important when developing a differential diagnosis. The following case illustrates how disease states may not always manifest as the textbooks say they should. In addition, it shows that practitioners must maintain a constant awareness of the potential side effects of the medications their patients may be taking, as well as understand how medicines may affect the already inconsistent presentation of disease states. This report, which presents a rare case, shows the impact and role of specific pharmacologic agents as the disease developed. The case also demonstrates the importance of history taking and how information that may appear trivial can lead to a diagnosis if the clinician is equipped with a firm foundation of medical knowledge.
Case report
A 63-year-old white man presented with a chief complaint of right-sided facial swelling that had increased over the prior 24 hours. During the initial examination in the office, he denied any fever, chills, rhinorrhea, or facial pain or pressure. In addition, he reported no associated visual changes or recent history of trauma to the affected area. On physical examination, there was obvious right-sided facial and periorbital swelling that greatly limited the patient's ability to open the right eye (see Figure 1). Subcutaneous crepitus was noted upon palpation of the involved area. 
The patient had an extensive medical history, but it appeared unrelated to his present problem. He had documented atherosclerotic coronary heart disease (CHD) with an MI in 1989 and triple coronary artery bypass graft surgery in 1991. He was taking aspirin, atenolol, diltiazem, and simvastatin for the CHD. In addition, over the past 2 years, he had suffered from degenerative disk disease with foraminal and central canal stenosis at C3-4 and C4-5.
Most recently, the patient had developed lower extremity symptoms, including difficulty walking that was related to a spastic gait, low back pain, and right-sided sciatic pain. Two weeks before onset of the facial swelling, he had seen his neurosurgeon, who recommended a course of dexamethasone, 2 mg every 8 hours, and rofecoxib, 25 mg daily, for an exacerbation of radicular (sciatic) pain. In addition, the patient was taking omeprazole 20 mg daily. He was a nonsmoker and admitted to occasional alcohol consumption.
Workup and treatment
Because of the unusual symptoms, concern about the possibility of severe infection, and the recent history of corticosteroid usage, the patient was admitted to the local hospital for further evaluation. Upon admission, his vital signs were as follows: temperature, 98.1°F (36.7°C); heart rate, 64 beats per minute; BP, 146/78 mm Hg; respiratory rate, 16 breaths per minute; and oxygen saturation, 94% on room air. Initial laboratory studies included a CBC with differential, a complete metabolic panel, and blood cultures. These revealed leukocytosis (WBC count, 32,400/mm3) with 92% polymorphonuclear cells, stable hemoglobin and hematocrit, mild hyperkalemia (potassium, 5.3 mEq/L), and slightly elevated ALT level (54 U/L). All blood culture results were eventually reported to be negative.
Differential diagnosis
Given the patient's physical presentation as well as the leukocytosis, the differential diagnosis at this point 
included a necrotizing soft tissue infection versus infection originating from a sinus or retropharyngeal location. The possibility was also considered, because of the crepitus and likely subcutaneous emphysema, that Clostridium perfringens had produced gas gangrene. Mucormycosal infection of the sinuses was also thought to be a possibility because of immunosuppression secondary to the corticosteroid usage. Tables 1 and 2 summarize the differential diagnosis of subcutaneous emphysema and acute facial swelling.
Mucormycosis, or rhinocerebral zygomycosis, is a fungal infection that typically occurs among patients who have diabetes or are immunocompromised. The infection develops in the nasal sinuses, progresses through the ethmoid sinuses into the retroorbital space, and eventually manifests late as periorbital edema, painful extraocular movement, and proptosis. Zygomycetes thrive among the acidic environments produced in diabetic ketoacidosis and in the presence of neutropenia associated with immunosuppression.