A 50-year-old woman comes to the office due to both of her feet feeling "asleep." Her symptoms have progressively worsened over the last 2 years and she occasionally stumbles while walking. She has no fatigue, weakness, pain, or other neurologic symptoms. The patient considers herself to be in good health and has no known medical problems. She has an average diet and does not drink alcohol.
Vital signs and general physical examination are within normal limits. BMI is 30 kg/m². Neurologic examination indicates bilateral decreased sensation to light touch and pinprick extending downward from the ankles. Ankle reflexes are absent and muscle strength is normal.
Which of the following would confirm the most likely cause of this patient's current symptoms?

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11ec193a_987a_4524_853d_95d9df380cf3_MD0002_00 This obese patient likely has diabetic neuropathy, the most common cause of peripheral neuropathy in adults. Up to 18% of patients with type 2 diabetes mellitus have evidence of nerve damage at the time of diagnosis, suggesting that prediabetes is associated with neuropathy. In addition, up to 50% of patients diagnosed with idiopathic peripheral neuropathy have prediabetes. Early detection is important as the incidence of diabetic neuropathy increases with time, and complications (eg, foot ulcer, Charcot arthropathy) may follow. Patients typically have numbness, paresthesias, and/or burning of the feet that insidiously spread in a stocking-glove distribution. Initially, sensation involving pain/temperature and vibration/proprioception may be impaired. Patients can also have diminished or absent ankle reflexes early in the disease. Frank muscle weakness may be a later finding in severe cases. (Choice A) Folic acid deficiency may cause megaloblastic anemia, but it is not typically associated with neurologic abnormalities such as peripheral neuropathy. (Choice C) Plasma cell dyscrasias are usually seen in older adults with symptoms of anemia, bone pain, fatigue, and renal disease. Peripheral neuropathy may occur due to associated amyloidosis but is not usually evident at the time of diagnosis. This patient's age and lack of these symptoms make plasma cell dyscrasias less likely. (Choice D) Long-standing hypothyroidism may result in a distal symmetric sensory neuropathy. However, this patient does not have other manifestations, such as fatigue, weight gain, cold intolerance, constipation, or bradycardia. (Choice E) Heavy metals can cause peripheral neuropathy; however, exposure is uncommon and neuropathy classically presents with extensor weakness (eg, wrist drop, ankle drop) and is rarely the sole symptom (eg, abdominal pain, myalgias, and cognitive difficulties noted in lead poisoning). In the absence of known exposure to heavy metals, more common causes (eg, diabetes) should be ruled out. Educational objective: Diabetic neuropathy is the most common cause of peripheral neuropathy in adults and may be associated with prediabetes. Early signs can include impaired sensation (eg, pain/temperature, vibration/proprioception) involving the feet and diminished ankle reflexes. Motor weakness may occur in advanced cases. __________ References: Peripheral neuropathy: differential diagnosis and management. (http://www.ncbi.nlm.nih.gov/pubmed/20353146)

A 50-Year-Old Woman Comes to the Office Due to Both