Denture cream: An unusual source of excess zinc, leading to hypocupremia and neurologic disease
MarcoSpinazzi, University of Padova
Mario Armani
Published October 28, 2008
We read with interest the article by Nations et al. describing four additional cases of copper deficiency myeloneuropathy in association with hyperzincemia and chronic use of denture creams containing zinc. [1]
We previously reported a patient with copper deficiency myeloneuropathy and zinc excess associated with over 15 years using a similar denture cream. [2] The daily amount of zinc oxide applied with the adhesive was about 150 mg. Even though there are no data on zinc bioavailability from this source, we agree with Nations et al. that these findings prompt important safety concerns on the chronic use of denture creams containing zinc.
Considering the potential detrimental effects to those exposed to these agents and the severe disability caused by copper deficiency myeloneuropathy, urgent verification is warranted. Even though many denture creams contain zinc, others do not. Those without zinc may contain polymethylvinyl ether/maleic acid and partial salts of sodium, calcium, magnesium. Therefore, clinicians treating patients with copper deficiency myeloneuropathy should ask patients about composition and usage before inferring a cause-effect mechanism.
Some patients with copper deficiency myeloneuropathy show evidence of zinc overload with elevated urine but not plasma zinc. [2-3] We observed persistent hyperzincuria with normal serum zinc in our patient for several years after she discontinued use of the denture cream. The underlying mechanism is unknown, but one hypothesis is that chronic zinc intoxication could have increased body zinc storage requiring long-term renal excretion of zinc or--less likely--a different, unknown mechanism of zinc overload. Therefore, we
suggest that follow-up of all the patients after zinc denture cream
discontinuation should always include 24-hour urine testing in addition to serum
zinc levels.
Moreover, the apparently limited prevalence of myeloneuropathy among denture cream users may suggest that unless an abuse of the denture cream occurs, as in some of the patients described by Nations et al. [1], additional factors could combine with zinc excess to precipitate the profound copper deficiency observed in this condition. Interestingly, many of the reported cases of copper deficiency myeloneuropathy showed evidence of both zinc excess and previous gastric surgery, malnutrition, or other malabsorption syndromes. [2-3]
It is possible that copper deficiency has a multifactorial genesis that should be specifically investigated, since some predisposing conditions may be subclinical (i.e., celiac disease) but increase the risk of recurrence of micronutrients deficiencies.
References
1. Nations SP, Boyer PJ, Love LA, et al. Denture cream. An unusual source of excess zinc, leading to hypocupremia and neurologic disease. Neurology 2008;71:639-643.
2. Spinazzi M, De Lazzari F, Tavolato B et al. Myelo-optico-neuropathy in copper deficiency occurring after partial gastrectomy. Do small bowel bacterial overgrowth syndrome and occult zinc ingestion tip the balance? J Neurol 2007;254:1012-1017.
3. Kumar N, Gross JB Jr, Ahlskog JE. Copper deficiency myelopathy produces a clinical picture like subacute combined degeneration. Neurology 2004;63:33-39.
Editor’s Note: The authors of the article were offered the opportunity to respond but declined.
We read with interest the article by Nations et al. describing four additional cases of copper deficiency myeloneuropathy in association with hyperzincemia and chronic use of denture creams containing zinc. [1]
We previously reported a patient with copper deficiency myeloneuropathy and zinc excess associated with over 15 years using a similar denture cream. [2] The daily amount of zinc oxide applied with the adhesive was about 150 mg. Even though there are no data on zinc bioavailability from this source, we agree with Nations et al. that these findings prompt important safety concerns on the chronic use of denture creams containing zinc.
Considering the potential detrimental effects to those exposed to these agents and the severe disability caused by copper deficiency myeloneuropathy, urgent verification is warranted. Even though many denture creams contain zinc, others do not. Those without zinc may contain polymethylvinyl ether/maleic acid and partial salts of sodium, calcium, magnesium. Therefore, clinicians treating patients with copper deficiency myeloneuropathy should ask patients about composition and usage before inferring a cause-effect mechanism.
Some patients with copper deficiency myeloneuropathy show evidence of zinc overload with elevated urine but not plasma zinc. [2-3] We observed persistent hyperzincuria with normal serum zinc in our patient for several years after she discontinued use of the denture cream. The underlying mechanism is unknown, but one hypothesis is that chronic zinc intoxication could have increased body zinc storage requiring long-term renal excretion of zinc or--less likely--a different, unknown mechanism of zinc overload. Therefore, we suggest that follow-up of all the patients after zinc denture cream discontinuation should always include 24-hour urine testing in addition to serum zinc levels.
Moreover, the apparently limited prevalence of myeloneuropathy among denture cream users may suggest that unless an abuse of the denture cream occurs, as in some of the patients described by Nations et al. [1], additional factors could combine with zinc excess to precipitate the profound copper deficiency observed in this condition. Interestingly, many of the reported cases of copper deficiency myeloneuropathy showed evidence of both zinc excess and previous gastric surgery, malnutrition, or other malabsorption syndromes. [2-3]
It is possible that copper deficiency has a multifactorial genesis that should be specifically investigated, since some predisposing conditions may be subclinical (i.e., celiac disease) but increase the risk of recurrence of micronutrients deficiencies.
References
1. Nations SP, Boyer PJ, Love LA, et al. Denture cream. An unusual source of excess zinc, leading to hypocupremia and neurologic disease. Neurology 2008;71:639-643.
2. Spinazzi M, De Lazzari F, Tavolato B et al. Myelo-optico-neuropathy in copper deficiency occurring after partial gastrectomy. Do small bowel bacterial overgrowth syndrome and occult zinc ingestion tip the balance? J Neurol 2007;254:1012-1017.
3. Kumar N, Gross JB Jr, Ahlskog JE. Copper deficiency myelopathy produces a clinical picture like subacute combined degeneration. Neurology 2004;63:33-39.
Editor’s Note: The authors of the article were offered the opportunity to respond but declined.
Disclosure: The authors report no disclosures.