A 56-year-Old Woman With Initial Severe Electrolyte Imbalance Who Developed Altered Mental Status, Psychosis and Catatonia.

Patients with acute psychiatric and cognitive symptoms can be challenging to evaluate, particularly in the context of renal or metabolic alterations. A 56-year-old woman initially presented with abdominal pain and vomiting, with no findings on physical examination. A severe chronic hypovolemic hypotonic hyponatremia was acknowledged in the lab work, leading to admission for sodium replacement and electrolyte imbalance correction. Two weeks later the patient developed altered mental status, agitation, psychosis and catatonia. This case highlights the diagnostic approach to patients with encephalopathy. Readers are guided through this stepwise approach, considering a wide range of differential diagnosis, including metabolic, infectious, autoimmune and paraneoplastic etiologies, with an extensive workup, ultimately arriving at the leading diagnosis.