A 48-year-old woman with diabetes mellitus comes to the office for a routine follow-up. The patient reports difficulty falling asleep and feeling exhausted and sleepy during the day over the past several weeks. On further questioning, she describes vague discomfort in her legs between the knees and ankles that is worse at night. The patient often gets out of bed to move around, which transiently improves the symptoms. She has a history of gestational diabetes and was diagnosed with type 2 diabetes mellitus 3 years ago for which she takes metformin. Her most recent hemoglobin A1c level was 7.6%. Blood pressure is 126/68 mm Hg and pulse is 76/min. BMI is 32 kg/m². Lower extremity examination shows scattered dilated superficial veins but no skin ulceration. Sensation to light touch and vibration is normal in the toes. Ankle and knee reflexes are normal bilaterally. Which of the following is the best next step in evaluation of this patient?

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11ec25c8_d580_fd82_bc81_3fc4fa8d97dc_MD0003_00 This patient has insufficient sleep due to nighttime leg discomfort that is temporarily alleviated by movement, which raises suspicion for restless legs syndrome (RLS). RLS is characterized by dysesthesia (eg, crawling and itching feelings) and an irresistible urge to move the legs when at rest. Symptoms occur primarily in the evenings and at night; they are partially relieved by movement. RLS does not cause pain or symptoms of peripheral neuropathy (eg, numbness, sensory deficits). It is classified as primary (if idiopathic) or secondary (if accompanied by an associated condition, like diabetes mellitus in this patient). Although its exact pathophysiology is unclear, RLS seems to be related to misuse of iron in the CNS; impairment of CNS dopaminergic systems, which are located close to the circadian control centers, may also play a role. Serum iron studies should be obtained in all patients with RLS. Patients with iron deficiency, or even low-normal ferritin levels (≤75 µg/L), should take supplemental iron, which often improves symptoms (Choice C). (Choices A and F) Peripheral artery disease can present with dull pain in the legs (ie, claudication); however, claudication worsens with walking and improves with rest. Venous ultrasonography is used to characterize chronic venous insufficiency, which can present with discomfort in the legs. Although dilated superficial leg veins may occur, patients typically have an aching or heavy feeling in the legs associated with swelling and skin changes (eg, dermatitis, ulceration). In contrast to RLS, pain increases when walking and improves when lying down (due to gravity assisting with venous drainage). (Choice B) Nerve conduction studies are sometimes used to diagnose peripheral neuropathy. Although diabetic neuropathy is common, it is classically in a stocking-glove distribution and tends to develop in patients who have had diabetes mellitus for an extended period of time, with significant hemoglobin A1c elevation (unlike this patient). This patient's nocturnal symptoms, relief with walking, and normal neurological examination (intact sensations) make RLS more likely. (Choice D) Overnight polysomnography is used to diagnose many sleep disorders (eg, obstructive sleep apnea). Although polysomnography may show periodic limb movements of sleep that sometimes accompany RLS, these findings are not specific for RLS, which is diagnosed by meeting clinical criteria. Educational objective: Restless legs syndrome (RLS) is a neurologic condition that can interfere with the quality and duration of sleep. It is characterized by an urge to move the legs and discomfort that is temporarily relieved by movement. Although RLS is diagnosed clinically, serum iron studies should be obtained; supplementation should be started in patients with low or low-normal ferritin levels. References: Restless legs syndrome: from pathophysiology to clinical diagnosis and management. (http://www.ncbi.nlm.nih.gov/pubmed/28626420) Differential diagnosis and treatment of restless legs syndrome: a literature review. (http://www.ncbi.nlm.nih.gov/pubmed/30443467)

A 48-Year-Old Woman with Diabetes Mellitus Comes to the Office