The following information may help to address your question:
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 (PBGD), an
enzyme also often called hydroxymethylbilane synthase. The low levels of PBGD 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 with nausea. Treatment is dependent on the symptoms.
[1]
Last updated: 11/11/2015
What are the signs and symptoms of acute intermittent porphyria (AIP)?
Some people who inherit the
gene for AIP never develop symptoms and are said to have "latent" AIP. 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. Symptoms usually last several days, but attacks for which treatment is not received promptly may last weeks or months.
[2]
Abdominal pain, which is associated with nausea and 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.,
insomnia, 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.
[2]
Last updated: 11/12/2015
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.
[1] The deficiency of PBGD is caused by a
mutation in the
HMBS gene. The
HMBS gene is the only gene known to be associated with AIP.
[2] However, the deficiency of PBGD alone is not enough to cause AIP. Other activating factors (e.g., hormones, drugs, dietary changes) must also be present.
[1]
Last updated: 11/12/2015
How is acute intermittent porphyria (AIP) inherited?
Last updated: 11/12/2015
How is acute intermittent porphyria (AIP) diagnosed?
Diagnosis of AIP is suspected in individuals with otherwise unexplained severe, acute abdominal pain without physical signs.
[2] The finding of increased levels of delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) in urine establishes that one of the acute porphyrias is present. If PBGD is deficient in normal red blod
cells, the diagnosis of AIP is established.
[1] 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: 11/12/2015
How might acute intermittent porphyria (AIP) be 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, treating any infections which may be present, administration of pain medication, monitoring fluid balance and/or correcting electrolyte disturbances, monitoring neurologic status and administering respiratory support. Mild attacks can be manged with increased caloric intake and fluid replacement. Recurrent acute attacks should be managed by a porphyria specialist.
[2] Hospitalization is often necessary.
[1] Panhematin, an intravenous medication used to correct heme deficiency, may also be prescribed.
[3] More detailed information about the use of Panhematin for the treatment of AIP can be found by
clicking here.
Last updated: 11/11/2015
Can acute intermittent porphyria (AIP) be disabling?
Acute intermittent porphyria can be severe and debilitating. During an acute attack, AIP may affect the 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 symptoms which are usually intermittent and can be life-threatening. The course of an acute attack is highly variable within an individual 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: 11/12/2015
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GARD Information Specialist
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