Lidocaine patch for pain of erythromelalgia.

A 15-year-old white girl had continuous mild discomfort associated with coolness and slight cyanosis of both feet. Intermittently, whenever she exercised, her feet became bright red and extremely painful, consistent with intermittent episodes of erythromelalgia (Figure 1). The discomfort markedly affected her daily activities: she stopped hiking, playing sports, marching in the high school band, and attending physical education classes. She could walk for only 10 minutes in the local shopping mall before her feet became red, hot, and too painful to continue walking. The vascular studies (described in detail elsewhere) performed included measurement of (1) blood pressure in affected extremities, (2) transcutaneous oxygen, and (3) temperature in the lower limb and digits. Because the patient’s symptoms were not elicited during these studies, the findings were unremarkable. Neurophysiologic testing (described in detail elsewhere) included nerve conduction studies, needle electromyography, and an autonomic reflex screen. The autonomic reflex screen included a quantitative sudomotor axon reflex test (QSART), heart rate response to deep breathing and Valsalva maneuver, and adrenergic function testing. The QSART assesses the integrity of both the axon reflex arch and sweat glands in the dermis. Acetylcholine is iontophoresed into 1 compartment, and sweat output is measured from a different compartment. A solution of 10% acetylcholine is injected into the first compartment and a constant current of 2 mA is applied for 5 minutes. Sweat output is measured for 5 minutes after stimulus discontinuation. The results showed a diffuse but patchy small-fiber neuropathy with marked anhidrosis of the lower extremities. The patient’s symptoms did not respond to fulldose, prolonged trials of aspirin (325 mg daily for 4 months), an -adrenergic blocker (doxazosin mesylate [Cardura; Pfizer-Roerig, New York, NY], 1 mg daily for 3 months), an anticonvulsant agent (gabapentin [Neurontin; Parke-Davis, Morris Plains, NJ]), a nonsteroidal antiinflammatory drug (50 mg of indomethacin, 3 times a day for 2 months), an oral antiarrhythmic agent (900 mg of mexiletine for 1 month; treatment was stopped because of gastrointestinal distress), and a tricyclic antidepressant drug (100 mg of nortriptyline daily for 21⁄2 months).