Several weeks before coming to our orthopedic surgery clinic, a 53-year-old man presented to an emergency department because of pain, swelling, and redness in his right foot, which began 3 days before. He recalled no overt trauma, but he was jogging when he first noticed the pain, which he described as a constant aching and rated as high as 8 on a scale of 10.
At that time, he had no fever, chills, or night sweats, no cough, and no shortness of breath. About 10 years ago he was diagnosed with diabetes mellitus, for which he currently takes rosiglitazone (Avandia) 2 mg/day and metformin (Glucophage XR) 500 mg four tablets daily. He also takes ramipril (Altace) 10 mg/day for hypertension, as well as a daily multivitamin. He has a history of hyperlipidemia and a family history of diabetes mellitus and Parkinson disease. He has never been hospitalized and has never undergone surgery.
His blood glucose level was 239 mg/dL (normal 70–110), hemoglobin A1c 9.7% (normal 4%–6%), and white blood cell count 13.41 × 109/L (normal 4.5–11.0).
Based on that evaluation, the patient was admitted to the hospital with a diagnosis of cellulitis. He received intravenous antibiotics for 3 days and then was discharged with a prescription for oral antibiotics. He visited his primary care physician several times over the next 2 to 4 weeks and then was referred to our orthopedic surgery clinic for further evaluation. A neurologic evaluation in our clinic revealed a loss of protective sensation, contraction of the toes, and dryness, consistent with peripheral neuropathy. Given what we know so far, which is the most likely diagnosis?
While cellulitis may seem to be the likely diagnosis, if a patient with long-standing diabetes, a history of poor glycemic control, and peripheral neuropathy presents with a red, hot, swollen foot with no history of open ulceration, then Charcot neuroarthropathy should be at the top of the list in the differential diagnosis. Other possibilities include osteomyelitis, acute gout, cellulitis, abscess, neuropathic fracture, and deep venous thrombosis. However, if the patient has no open ulceration or history of an open wound, infection is probably not the culprit. Most diabetic foot infections begin with a direct inoculation through an opening in the skin, such as a diabetic neuropathic foot ulcer.
Further, in the case of cellulitis or deep venous thrombosis, the predominating feature would be asymmetric edema of the leg. Also, the location of the edema and ecchymosis in our patient—namely, the midfoot—leads to suspicion of an acute musculoskeletal injury, particularly Charcot neuroarthropathy of the midfoot and neuropathic fractures in the region of the ecchymotic second and third digits. Acute gout could be discounted because gout pain is severe, with rapid onset, and slowly improves even without treatment.
A COMPLICATION OF DIABETES
Charcot neuroarthropathy presents as a warm, swollen, erythematous foot and ankle, a picture that may be indistinguishable from that of infection. Most patients are in their 50s or 60s, and most present on an emergency basis; they often present late in the process, ie, 2 to 3 months after the initial symptoms, because the symptoms often are not painful.
This condition has been reported to occur with leprosy, syringomyelia, toxic exposure, poliomyelitis, rheumatoid arthritis, multiple sclerosis, congenital neuropathy, traumatic injury, and tertiary syphilis.1–4 Other conditions that reportedly trigger it include cellulitis, osteomyelitis, synovitis, surgery of the foot, and renal transplant surgery.5–7 However, today, the most common cause is diabetes mellitus.4,8
Other names for this condition are diabetic neuropathic osteoarthropathy and neuropathic arthropathy.
Current estimates of its prevalence range from 0.08% in the general diabetic population to 13% in high-risk diabetic patients.9