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Genetic and Rare Diseases Information Center (GARD)

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Acute intermittent porphyria

Other Names for this Disease
  • AIP
  • HMBS deficiency
  • Hydroxymethylbilane synthase deficiency
  • PBGD deficiency
  • Porphobilinogen deaminase deficiency
More Names
Related Diseases
More Related Diseases
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Your Question

I was recently diagnosed with acute intermittent porphyria. I would like to learn more about this condition. I was also informed some time ago that the porphyrias can be disabling. What information can you provide?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is acute intermittent porphyria (AIP)?

Acute intermittent porphyria (AIP) is one of the liver (hepatic) porphyrias. AIP is caused by low levels of porphobilinogen deaminase (PGBD), an enzyme also often called hydroxymethylbilane synthase. The low levels of PGBD are generally not sufficient to cause symptoms; however, activating factors such as hormones, drugs, and dietary changes may trigger symptoms. Although most individuals with AIP never develop symptoms, symptomatic individuals typically present with abdominal pain. Treatment is dependent on the symptoms.[1] 
Last updated: 10/23/2009

What are the symptoms of acute intermittent porphyria (AIP)?

Some people who inherit the gene for AIP never develop symptoms and are said to have "latent" AIP.[2]  Those individuals that present with symptoms usually do so after puberty, probably because of hormonal influences, although other activating factors include: alcohol, drugs (e.g., barbiturates, steroids, sulfa-containing antibiotics), chemicals, smoking, reduced caloric intake, stress, and travel).[2] Symptoms usually last several days, but attacks for which treatment is not received promptly may last weeks or months.[2]

Abdominal pain, which can be severe, is the most common symptom and usually the first sign of an attack. [1][2]

Other symptoms may include [1][2]:

• Gastrointestinal issues (e.g., nausea, vomiting, constipation, diarrhea, abdominal distention, ileus)
• Urinary tract issues (e.g., urinary retention, urinary incontinence, or dysuria)
• Neurological issues (e.g., muscle weakness in the arms or legs, paralysis)
• Psychiatric issues (e.g., hysteria, anxiety, apathy or depression, phobias, psychosis, agitation, delirium, somnolence, or coma)

Individuals with AIP have an increased risk of developing hepatocellular carcinoma; some develop kidney failure.[1]
Last updated: 6/27/2011

What causes acute intermittent porphyria (AIP)?

AIP is caused by the deficiency of an enzyme called porphobilinogen deaminase (PBGD), also known as hydroxymethylbilane synthase (HMBS) and formerly known as uroporphyrinogen I-synthase. The deficiency of PBGD is caused by a disease-causing mutation in the HMBS gene.  The HMBS gene is the only gene known to be associated with AIP.[1]
Last updated: 10/23/2009

How is acute intermittent porphyria (AIP) inherited?

AIP is inherited in an autosomal dominant fashion, which means only one of the two HMBS genes needs to have a disease-causing mutation to decrease enzyme activity and cause symptoms.[2] 
Last updated: 10/23/2009

How is acute intermittent porphyria (AIP) diagnosed?

Diagnosis of AIP is suspected in individuals with neuropsychiatric symptoms and biochemical findings, including increased excretion of δ-aminolevulinic acid (ALA) and porphobilinogen (PBG); measurement of urinary PBG is the best biochemical test for AIP. Tests for urinary PBG include the Watson-Schwartz test for rapid detection and ion-exchange column chromatography for greater sensitivity. The diagnosis is confirmed in individuals with a disease-causing mutation in the HMBS gene, the only gene known to be associated with AIP, which encodes the erythrocyte hydroxymethylbilane synthase enzyme. Molecular genetic testing of the HMBS gene detects more than 98% of affected individuals and is available in clinical laboratories.[2] To obtain a list of clinical laboratories offering genetic testing for AIP, click here.
Last updated: 10/23/2009

How is acute intermittent porphyria (AIP) treated?

Treatment of AIP may vary based on the trigger of the attack and the symptoms present. Treatment may include stopping medications that cause or worsen the symptoms.[2] A high carbohydrate diet is recommended for patients with porphyria, however, it is not regarded as highly effective by itself. Intravenous glucose therapy is a treatment option for mild attacks. Panhematin may also be prescribed.[3] More detailed information about the treatment of AIP can be found by clicking here.
Last updated: 10/23/2009

Can acute intermittent porphyria (AIP) be disabling?

Acute intermittent porphyria can be severe and debilitating. When "manifest", clinically expressed as an acute attack, AIP affects visceral (internal organ), peripheral (affecting the peripheral nerves - nerves to the hands and feet), autonomic, and central (brain and spinal cord) nervous systems, leading to a wide variety of manifestation, which are usually intermittent and sometimes life-threatening. The course of an acute attack is highly variable within an indivdual as well as among individuals. Affected individuals may recover from acute attacks within days, but recovery from severe attacks that are not promptly recognized and treated may take weeks or months.[2] 
Last updated: 6/9/2009