Suspected hemolytic anemia secondary to acute zinc toxicity after ingestion of “max strength” (zinc oxide) diaper rash cream

Abstract

Objective: To describe the clinical presentation of a dog with hemolytic anemia secondary to zinc toxicosis after 1-week use of "max strength" 40% diaper rash cream.Case Summary: A 2-year-old female neutered Maltese presented for vomiting, lethargy, pigmenturia, and pale mucous membranes. "Max Strength" zinc oxide cream had been applied to the patient daily for a week prior to presentation. Clinical examination revealed light pink to pale mucous membranes and tachycardia. Hematology demonstrated large numbers of spherocytes and a strongly regenerative anemia.Plasma zinc concentrations were markedly increased. A diagnosis of hemolytic anemia secondary to subacute zinc toxicosis was made and supportive therapy was instigated.The patient ultimately recovered uneventfully. Acute or subacute zinc toxicosis resulting in hemolytic anemia is not frequently observed, and this case was also unusual in that the zinc source was diaper cream, which historically has been thought to require very large quantities to cause toxicosis. New or Unique Information Provided:To the authors' knowledge, there is only one previously reported case of hemolytic anemia secondary to diaper cream use in a hospital setting but no previous reports involving toxicosis secondary to prolonged application at home by owners. Most commercial diaper creams contain zinc oxide, which historically was thought to have poor gastrointestinal absorption and would require a large quantity to cause significant toxicosis and hemolytic anemia. Moreover, this case emphasizes the potential risks associated with zinc oxide cream use, the significance of client education if using these creams, as well as the importance of history in elucidating the underlying cause of hemolytic anemia.

Retrospective evaluation of the clinical course and outcome of zinc toxicosis due to metallic foreign bodies in dogs (2005–2021): 55 cases

“…Although previously suggested that signs of toxicity develop when serum concentrations reach or exceed 5–10 ppm, cases in the current study where zinc concentrations were tested developed clinical signs at lower concentrations and had lasting effects after MFB removal 5,19 . Additionally, it has been proposed that zinc toxicity due to MFBs may depend heavily on the pH of the stomach, the type of zinc compound or zinc salt ingested and its ability to ionize free zinc, the presence of stomach contents such as recent meals or specific proteins, the size of the dog, and the exposure to other heavy metals and minerals present in the gastrointestinal tract 7,8,16 …”

“…However, it also affects the gastrointestinal tract by direct irritation and ulceration as well as the organs in which it has a propensity to accumulate (ie., liver, kidney, spleen, and pancreas) 1,4,7 . The current toxic dose for zinc in dogs is not definitively established, as both the toxic dose (TD 50 ) and more commonly the lethal dose (LD 50 ) are reported to be as low as 100 mg of zinc salt per kilogram of body weight 1,4,8 …”

“…Given most dogs presenting for zinc MFBs are under 12 kg, a single penny contains over twice the estimated lethal dose for these dogs and could potentially kill a 25‐kg dog 4,5 . Other MFBs documented to cause zinc toxicosis include zinc‐coated or galvanized hardware, children's toys, Christmas garland, identification tags, jewelry, and zippers 4,8,11,12 . Zinc oxide, commonly used in diaper creams and sunblock, was previously thought to result in clinical signs limited to gastrointestinal upset 4,5 .…”

“…This is largely thought to be because zinc oxide does not readily dissociate to ionized components as readily as MFBs 4 . However, a recent publication confirmed toxic serum zinc concentrations resulting in severe transfusion‐dependent hemolytic anemia in a dog with repeated ingestion of diaper rash cream containing zinc oxide 8 …”

“…1,4,7 The current toxic dose for zinc in dogs is not definitively established, as both the toxic dose (TD 50 ) and more commonly the lethal dose (LD 50 ) are reported to be as low as 100 mg of zinc salt per kilogram of body weight. 1,4,8 The exact pathophysiology of hemolytic anemia and other organ injury in zinc toxicosis is incompletely understood. The proposed mechanism is that of oxidative damage via inhibition of the glutathione reductase pathway and enzymes involved in the hexose monophosphate shunt pathway, resulting in oxidative damage and subsequent hemolysis.…”