6th February 2024

A 34-year-old female presents with intermittent severe abdominal pain for the past six months.

A 34-year-old female presents with intermittent severe abdominal pain for the past six months. This is described as a colicky abdominal pain without clear triggers and constipation. All routine investigations have been negative. On her current admission, her mother reports a similar episode of abdominal pain associated with significant confusion. While inpatient, she experienced a 1-minute generalised tonic-clonic seizure requiring lorazepam to terminate. Dark-red urine was observed within her catheter bag. The physical examination was unremarkable. Blood tests today showed a hyponatremia and hypomagnesemia. Urinary ALA levels were elevated. 

Which of the following is the likely underlying diagnosis?