Phenytoin-induced Hypothermia in a Patient with Mental Retardation

Background: Phenytoin toxicity presenting as hypothermia has been reported in patients with mental retardation (MR), without causative explanation. We report a case in a patient with adrenal insufficiency. Case Report: A 50-year-old man with a history of MR and seizures was found lethargic. Medications included phenytoin and phenobarbital. Physical examination was unremarkable except for somnolence and hypothermia. The serum phenytoin level was 37 μg/mL (147 μmol/L). A cosyntropin stimulation test showed adrenal insufficiency. No infectious or inflammatory conditions were identified. The patient improved with supportive care, antibiotics and steroids. Discussion: The mechanism of phenytoin-associated hypothermia is unknown. It may be centrally mediated, or phenytoin may exert an indirect effect on hepatic steroid clearance leading to relative adrenal insufficiency. Conclusion: Significant hypothermia may occur with phenytoin toxicity. Clinicians should be alerted to this possibility and check a core temperature on patients at risk.