Possible anti-VGKC autoimmune limbic encephalitis associated with SIADH.

Area of Science:

• Neurology
• Endocrinology

Background:

• Syndrome of inappropriate antidiuretic hormone (SIADH) can cause hyponatraemia and neurological symptoms.
• Autoimmune limbic encephalitis is a rare cause of cognitive decline and psychiatric disturbances.

Observation:

• An 80-year-old woman presented with progressive confusion, short-term memory deficits, and paranoia.
• Biochemical tests confirmed hyponatraemia and SIADH.
• A mildly elevated anti-voltage-gated potassium channel (VGKC) antibody titre was detected.

Findings:

• The patient's presentation was consistent with SIADH, but other causes of limbic encephalitis were not definitively identified.
• The elevated anti-VGKC titre raised suspicion for autoimmune limbic encephalitis, despite the absence of other typical diagnostic features.

Implications:

• This case highlights the importance of considering autoimmune encephalitis in elderly patients with unexplained cognitive and psychiatric symptoms, even with atypical presentations.
• Further investigation is warranted to determine the precise cause of memory loss and to guide appropriate management.