[Diagnostic trap: Lithium neurotoxicity with normal lithemia]

Area of Science:

• Nephrology
• Psychiatry
• Clinical Toxicology

Context:

• A 54-year-old female patient with bipolar disorder was undergoing treatment with lithium, escitalopram, and lamotrigine.
• The patient presented with an altered state of consciousness, raising suspicion of lithium toxicity.

Purpose:

• To report a case of lithium poisoning diagnosed despite seemingly therapeutic blood lithium levels.
• To emphasize the importance of clinical presentation and biological markers in diagnosing lithium toxicity.

Summary:

• Neurological symptoms suggested lithium poisoning, but initial blood tests showed lithium levels at the upper limit of the therapeutic range (1.2 mmol/L).
• The diagnosis was confirmed by the presence of classic biological complications: hypercalcemia and diabetes insipidus.
• Hemodialysis was administered, resulting in clinical and biological improvement, validating the diagnosis of lithium poisoning.

Impact:

• This case underscores that lithium poisoning can occur even with blood levels within the accepted therapeutic range.
• It highlights the critical role of recognizing clinical signs and biological complications for accurate diagnosis and management of lithium toxicity.
• The findings suggest a need for careful monitoring and individualized treatment adjustments in patients on lithium therapy.