Introduction

Acute intermittent porphyria (AIP) is a rare autosomal dominant condition caused by a defect in porphobilinogen deaminase, an enzyme involved in the biosynthesis of haem. The results in the toxic accumulation of delta aminolaevulinic acid and porphobilinogen. It characteristically presents with abdominal and neuropsychiatric symptoms in 20-40 year olds. AIP is more common in females (5:1)

Epidemiology

  • Incidence: 0.01 cases per 100,000 person-years
  • Peak incidence: 30-40 years
  • Sex ratio: more common in females 5:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Clinical features

The classical presentation is a combination of abdominal, neurological and psychiatric symptoms:

Investigations

  • classically urine turns deep red on standing
  • raised urinary porphobilinogen (elevated between attacks and to a greater extent during acute attacks)
  • assay of red cells for porphobilinogen deaminase
  • raised serum levels of delta aminolaevulinic acid and porphobilinogen

Management

Drugs which may precipitate attack
  • barbiturates
  • halothane
  • benzodiazepines
  • alcohol
  • oral contraceptive pill
  • sulphonamides

Drugs considered safe to use
  • paracetamol
  • aspirin
  • codeine
  • morphine
  • chlorpromazine
  • beta-blockers
  • penicillin
  • metformin