Discussion
The case presented here taught us two important lessons. First, relatively low doses of lithium could cause toxicity in patients with poor general health, such as those suffering from progressive stage cancer. Second, clinicians often fail to diagnose delirium associated with lithium poisoning. In this particular case, the general condition of the patient was poor and fluid intake was reduced, which led to a decrease in renal function, in turn causing a decrease in excretion. The end result was the appearance of symptoms of poisoning. In addition, the patient was in the terminal stages of cancer and had been treated with anticancer drugs, which may have predisposed her to the observed decline in renal function. Nevertheless, a daily dose of 300 mg/day is considered low according to current literature 7, which underlines the idea that even low doses of the drug could easily lead to poisoning. Brain metastases, electrolyte abnormalities, and terminal delirium are the most common causes of psychiatric symptoms in cancer patients at the terminal stage 9, 10. Taking the case presented here into account, lithium intoxication should be considered as a possible diagnosis when myoclonus and gait disturbances are observed. We should also be aware of the fact that serum lithium levels often do not correlate with clinical signs 7. Lithium poisoning should always be considered as a potential cause for prolonged delirium 7.