What is the definition of Acute Intermittent Porphyria?
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.
What are the alternative names for Acute Intermittent Porphyria?
- Porphobilinogen deaminase deficiency
- PBGD deficiency
- Uroporphyrinogen synthase deficiency
- UPS deficiency
- Porphyria, Swedish type
- Hydroxymethylbilane synthase deficiency
- HMBS deficiency
What are the causes for Acute Intermittent Porphyria?
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 mutation in the HMBS gene. The HMBS gene is the only gene known to be associated with AIP. 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.
What are the symptoms for Acute Intermittent Porphyria?
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.
Abdominal pain, which is associated with nausea and can be severe, is the most common symptom and usually the first sign of an attack.
Other symptoms may include :
• 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.
Is Acute Intermittent Porphyria an inherited disorder?
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.