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
Is it possible for an individual who has the disease-causing mutation for acute intermittent porphyria (AIP) to remain asymptomatic?
Some people who inherit the gene for AIP never develop symptoms and are said to have "latent" AIP.
[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
Can asymptomatic individuals be tested for acute intermittent porphyria (AIP)?
Testing of at-risk asymptomatic adults for AIP is available using either assay of
erythrocyte HMBS enzyme activity or, if the
mutation is known in an
affected family member,
molecular genetic testing of the
HMBS gene. Such testing is not useful in predicting whether individuals who inherit an
HMBS mutation will be symptomatic, or if they are, the age of onset, severity, or type of symptoms. Before testing at-risk individuals for AIP, it is necessary to first test an
affected family member to confirm that the disorder in the family is actually AIP.
[2]
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 old must one be in order to be tested for acute intermittent porphyria (AIP)?
Although most testing is done in adults, there may be an advantage to testing at-risk asymptomatic individuals prior to puberty, as symptoms most often develop after this age. Identification of individuals at risk for AIP may alter management because avoidance of known
risk factors may be helpful in preventing acute attacks and afford prompt treatment should an attack occur.
[2]
Last updated: 11/12/2015
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GARD Information Specialist
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