Introduction
Lithium remains the drug of choice for the treatment of bipolar disorder1 and is identified as the first-line agent for this
disease in many guidelines 2. However, due to its
narrow therapeutic index, small changes in the serum concentration of
lithium can cause toxicity or render the treatment ineffective3. The major symptoms of lithium poisoning include
tremors, hyperreflexia, gait disturbances, kidney damage, and reduced
self-awareness 4; it can sometimes lead to death of
the affected individual. Lithium intoxication has three different
courses (acute, acute-chronic, and chronic) 5. Among
these, the chronic course is the most common etiology, usually resulting
from an unintentional excess of lithium intake over excretion6. Chronic lithium
poisoning also presents a higher
risk of serious complications than acute poisoning 5.
A retrospective study on the neurotoxicity associated to lithium intake
revealed that chronic poisoning mainly occurs in older patients with
chronically elevated lithium levels, especially in those with acute
kidney injury, and that prolonged delirium can lead to multiple physical
complications 7. In addition, it was found that
patients affected by chronic lithium poisoning had a median lithium
concentration in serum of 2.2 mmol/L (interquartile range: 1.0–7.1
mmol/L) at presentation and received a median daily dose of 950 mg/day
(interquartile range: 250–1350 mg/day). This suggests that even small
doses of lithium can lead to poisoning. Here, we report a case of
schizoaffective disorder in a patient with cancer at the progressive
stage that was being treated with lithium at a low dose of (300 mg/day).
In this particular case, the clinical symptoms were masked because of
the patient’s poor physical status resulting from the progressive stage
of cancer disease.