Acute Intermittent Porphyria
National Organization for Rare Disorders, Inc.
It is possible that the main title of the report Acute Intermittent Porphyria is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.
Acute intermittent porphyria (AIP) is a rare metabolic disorder that is characterized by deficiency of the enzyme porphobilinogen deaminase (also known as hydroxymethylbilane synthase). This enzyme deficiency can result in the accumulation of porphyrin precursors in the body. This enzyme deficiency is caused by a mutation in the HMBS gene and is inherited as an autosomal dominant trait (only one HMBS gene copy is affected). However, the deficiency by itself is not sufficient to produce symptoms of the disease and most individuals with a HMBS gene mutation do not develop symptoms of AIP. Additional factors such as endocrine factors (e.g. hormonal changes), the use of certain drugs, excess alcohol consumption, infections, and fasting or dietary changes are required to trigger the appearance of symptoms. Symptoms include severe abdominal pain, constipation, muscle weakness, a rapid heartbeat (tachycardia), behavioral changes, seizures, and disease of the nerves outside of the central nervous system (peripheral neuropathy). Treatment is focused on preventing attacks by educating patients to avoid potential triggers. Acute attacks usually require hospital care and can be effectively treated with intravenous hematin.
AIP belongs to a group of disorders known as the porphyrias. This group of disorders is characterized by abnormally high levels of porphyrins and porphyrin precursors due to deficiency of certain enzymes essential to the creation (synthesis) of heme, a part of hemoglobin and other hemoproteins found in all cells. There are eight enzymes in the pathway for making heme and at least seven major forms of porphyria. The symptoms associated with the various forms of porphyria differ. It is important to note that people who have one type of porphyria do not develop any of the other types. Porphyrias are generally classified into two groups: the "hepatic" and "erythropoietic" types. Porphyrins and porphyrin precursors and related substances originate in excess amounts predominantly from the liver in the hepatic types and mostly from the bone marrow in the erythropoietic types. Porphyrias with skin manifestations are sometimes referred to as "cutaneous porphyrias." The term "acute porphyria" is used to describe porphyrias that can be associated with sudden attacks of pain and other neurological symptoms. Two porphyrias can have cutaneous and acute symptoms, sometimes together. Most forms of porphyria are genetic inborn errors of metabolism. AIP is an acute, hepatic form of porphyria.
CLIMB (Children Living with Inherited Metabolic Diseases)
176 Nantwich Road
Crewe, CW2 6BG
American Porphyria Foundation
4900 Woodway, Suite 780
Houston, TX 77056-1837
British Porphyria Association
136 Devonshire Rd
Durham City, DH1 2BL
Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
Norwegian Porphyria Centre
Haukeland University Hospital
Jonas Liesvei 65
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Last Updated: 5/1/2008
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