Copper Deficiency Induced Neuropathy: A Sticky Situation

Abstract

Purpose: Acquired copper deficiency, which can manifest as peripheral neuropathy, can be precipitated by gastrointestinal surgery, malabsorption, and nutritional deficiencies. Rarely, zinc toxicity can also cause hypocupremia. We report a case of acquired copper deficiency secondary to zinc toxicity caused by chronic use of denture adhesives. Methods: A 72 year-old male presented to the emergency department with a chief complaint of difficulty walking. The patient described a six-month history of lower extremity weakness and decreased sensation bilaterally. The patient denied palpitations, slurred speech, or discordination. He also denied weight loss, floating or malodorous stools, skin pigment changes, abdominal distention, or past gastrointestinal surgery. On physical exam, the patient was noted to be wearing dentures. There was no spider angioma, palmour erythema, or jaundice noted. Rectal exam demonstrated normal brown stool, which was guaiac negative. Results: Electroencephalogram (EEG) and neurological Magnetic Resonating Imaging (MRI) of the brain and spinal cord were within normal limits. CSF analysis was negative for viral, fungal, and bacterial cultures. Initial electrolytes and mineral values were all within normal limits except for a ceruloplasmin level of 4 mg/dL (nml 20-60), and a copper level <10 ug/dL (nml >65). Subsequent gastrointestinal work up revealed normal liver enzymes and negative endosysial, gliadin, and transglutamanaise antibodies. Additional nutritional studies demonstrated a zinc level of 1.52 mcg/dL (0.6-1.1). The patient received two weeks of IV copper with complete resolution of symptoms. Conclusion: Copper deficiency is a known cause of peripheral neuropathy. Acquired copper deficiency can be caused by gastrointestinal surgery, malabsorption, and nutritional deficiency. Zinc toxicity can also lead to hypocupremia although the exact etiology remains unknown. In recent years, a correlation between denture adhesive cream and zinc toxicity has been reported. It is estimated that a tube of Fixodent® has from 17 to 34 mg of zinc, which exceeds the NIH's recommended daily allowance of 8 mg in adult females and 11 mg in adult males. Previous studies have demonstrated that extensive denture adhesive use (two or more tubes a week for several years) can result in neurological manifestations such as peripheral neuropathy. Copper deficiency secondary to zinc toxicity should be considered in the differential in patients with chronic denture use presenting with neuropathy.