Acute intermittent porphyria: A rare cause of syndrome of inappropriate antidiuretic hormone secretion.

A 31-year-old female presented to the emergency department with abdominal pain, vomiting and constipation. Serum sodium levels were recorded at 110 mmol/L on admission, dropping to 96 mmol/L despite fluid restriction. The patient developed hallucinations and required hypertonic saline administration in critical care. Urinary sodium was detected at 149 mmol/L, consistent with syndrome of inappropriate antidiuretic hormone secretion (SiADH). Urinary porphyrins were also raised, consistent with a diagnosis of acute intermittent porphyria with SiADH as a complication.