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For further information, see CMDT Part 40-16: Acute Intermittent Porphyria

Key Features

Essentials of Diagnosis

  • Unexplained abdominal crisis, generally in young women

  • Acute central or peripheral nervous system dysfunction

  • Recurrent psychiatric illnesses

  • Hyponatremia

  • Porphobilinogen in the urine during an attack

General Considerations

  • Acute intermittent porphyria is caused by partial deficiency of hydroxymethylbilane synthase activity, leading to increased excretion of aminolevulinic acid and porphobilinogen in the urine

  • Genetics: mutation in the porphobilinogen deaminase gene

  • Autosomal dominant inheritance

  • It remains clinically silent in the majority of patients who carry a mutation in HMBS

  • Characteristic abdominal pain may be due to abnormalities in autonomic innervation in the gut

  • Cutaneous photosensitivity is absent

  • Attacks precipitated by numerous factors, including drugs and intercurrent infections

  • Hyponatremia resulting from inappropriate release of antidiuretic hormone and gastrointestinal loss of sodium


  • Usually presents in adulthood and has serious consequences

  • Clinical illness usually develops in women

  • Symptoms beginning in the teens or 20s, but in rare cases after menopause

Clinical Findings

Symptoms and Signs

  • Intermittent abdominal pain of varying severity, sometimes simulating an acute abdomen

  • Absence of fever and leukocytosis

  • Complete recovery between attacks

  • Autonomic neuropathy

  • Peripheral neuropathy, symmetric or asymmetric, mild or profound

  • CNS manifestations include

    • Seizures

    • Altered consciousness

    • Psychosis

    • Abnormalities of the basal ganglia

Differential Diagnosis

  • Acute abdominal pain resulting from other cause, such as

    • Appendicitis

    • Peptic ulcer disease

    • Cholecystitis

    • Diverticulitis

    • Ruptured ectopic pregnancy

    • Familial Mediterranean fever

  • Polyneuropathy resulting from other cause

  • Guillain-Barré syndrome

  • Lead or other heavy metal poisoning

  • Psychosis resulting from other cause

  • Syndrome of inappropriate antidiuretic hormone resulting from other cause

  • Dark urine resulting from other cause (eg, alkaptonuria)


Laboratory Tests

  • Hyponatremia, often profound

  • Freshly voided urine is of normal color but may turn dark upon standing in light and air

  • Urine porphobilinogen increased during an acute attack

  • Most families have different mutations in HMBS

  • Mutation detection in the gene for porphobilinogen deaminase



  • Analgesics

  • Intravenous glucose

  • High-carbohydrate intake, a minimum of 300 g carbohydrate/day orally or intravenously

  • Hematin up to 4 mg/kg intravenously once or twice daily

  • Adverse consequences of hematin therapy include phlebitis and coagulopathy

Therapeutic Procedures

  • High-carbohydrate diet diminishes the number of attacks

  • Withdrawal of the inciting agent

  • Liver transplantation for extreme cases



  • ECG

  • Electrolytes

  • Glucose

  • Mental status


  • Avoidance of factors known to precipitate attacks, especially drugs (Table 40–1)

  • Starvation diets must be avoided

  • Hormonal changes ...

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