Ethylene glycol poisoning with a normal anion gap due to occult bromide intoxication

Ethylene glycol poisoning causes metabolic acidosis with an increased anion gap, due to production of organic acid anions during its metabolism. Bromide poisoning may cause a spuriously decreased anion gap when chloride determination is performed with a colorimetric technique. A 39-year-old woman with ethylene glycol poisoning presented in coma, with a hyperchloremic normal anion gap acidosis. The serum bromide level was found to be in the toxic range, confirming the diagnosis of bromide poisoning. Hemodialytic therapy resulted in resolution of electrolyte and acid-base abnormalities, and restoration of a normal state of consciousness. In this patient, clinically occult bromide intoxication caused a spurious lowering of the anion gap, normalizing what was in reality an increased anion gap due to ethylene glycol poisoning.