[Lithium intoxication in a patient with severe motor and intellectual disabilities]

A severaly retarded 30-year-old woman developed acute lithium intoxication. Since the age of 22, she had been treated with neuroleptics for her aggressive behavior. At 30 years of age, lithium carbonate was added to arrest self-injurious behavior, at an initial dosage of 300 mg/day and a maintenance dosage of 900 mg/day. She subsequently developed anorexia and weight loss, and was admitted to our hospital. After 7 months of lithium therapy, she suddenly had a high fever (38.3 degrees C), diabetes inspidus, severe hypernatremia, and became akinetic and mute. Under the suspicion of lithium intoxication, all medication was discontinued, and mannitol to increase renal lithium clearance. She was given gradually improved over a month, but remained hypothyroid. This case shows the importance of interaction of lithium carbonate and other drugs which may cause lithium intoxication. In patients with severe intellectual disabilities who are unable to complain their symptoms, lithium therapy requires particularly close attention to signs of early toxicity.