[A case of lithium intoxication with reversible parkinsonism]

A 73-year-old man, who had been treated for bipolar disorder since he was 39 years old, was admitted because he had developed difficulty in walking and moving his hands for the past 2 months. He was suspected of having Parkinson's syndrome. On admission, his blood lithium level was at the upper limit of normal (1.34 mEq/l), but his food intake gradually decreased and his communication difficulties worsened. On the sixth day of hospitalization, his blood lithium level was in the toxic range (2.44 mEq/l). His general condition, including motor symptoms, improved after lithium medication was discontinued and infusions (normal saline) were started. On the 24th day of admission, he was transferred to the psychiatry department for a psychotropic medication adjustment. It is important to note that chronic intoxication can occur even at the upper limit of the therapeutic range and that salt reduction at the start of the inpatient diet may be a trigger for intoxication.