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Diseases Studied

The Rare Diseases Clinical Research Network is an NIH-funded research network of 20 active consortia or research groups working to advance treatment for diseases that are rare. Use the search tools on this page to find the diseases we currently study. You can reach out to the indicated consortia or research groups for more information on those diseases and studies underway.

This network focuses on clinical research and does not generally support clinical care outside of research activities. To learn about other rare diseases, please visit the Genetic and Rare Diseases Information Center (GARD), which is an NIH program that helps the public find reliable information about rare and genetic diseases. Their staff are specialists. Contact them at 1-888-205-2311 or email

All Diseases > Acute intermittent porphyria

Acute intermittent porphyria (AIP)

Disease Category: Porphyrias

A rare, inherited, metabolic disorder characterized by partial deficiency of the enzyme hydroxymethylbilane synthase, which allows for build-up of porphyrin precursors throughout the body. Porphyrins are substances that bind metals to form complexes, such as the iron found in red blood cells. Symptoms include severe abdominal pain, constipation, rapid heartbeat, high blood pressure, seizures, behavioral changes, and peripheral neuropathy (sensory changes and profound muscle weakness in the extremities). Symptoms occur following triggers such as infections, hormonal changes, drug and alcohol abuse, and dietary changes.

Research groups studying this disease

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The porphyrias are a group of rare metabolic diseases that may present in childhood or adult life and are due to deficiencies of enzymes in the heme biosynthetic pathway. Porphyrias have various symptoms depending on the type, but these can range from neurological symptoms to sun sensitivity. See the descriptions of each type to get more information. The natural history of these disorders is not well described and it is not known why some patients are more severe than others. Therefore, the purpose of this long-term follow-up study is to collect a large group of patients with the different types of porphyria and to provide a better understanding of the natural history of these disorders. The hope is that this information will help in developing new forms of treatment. The research aims are: 1. To study the prevalence of specific indicators of disease severity. To study the effects on quality of life and health of various porphyrias. 2. To determine the relationships between disease severity and various biological characteristics, genetic information, and environmental factors.

The purpose of this study is to collect information on acute porphyria attacks that may have been caused by a medication. Individuals who have tested positive for an acute porphyria, or have been told by a doctor that they may have the disease may join this study. We are particularly interested in the following: (1) Attacks that appeared to be due to a specific medication; (2) Use of a medication that is considered risky in porphyria but caused no problems; and (3) Use of medications for which the safety profile in porphyria is unknown.

AIP is rare a genetic disorder caused by mutations in the hydroxymethylbilane synthase gene (HMBS) that reduce the function of an enzyme (a type of protein) in the body that is necessary for the production of heme. Heme is important for your body to use oxygen and for your liver to work properly. When a person does not produce enough of this enzyme, substances called ALA and PBG can accumulate, and this can cause symptoms of AIP. These symptoms may include abdominal pain; pain in the arms, legs and back; muscle weakness; nausea and vomiting; and confusion, hallucinations, and seizures. A small portion of AIP patients have recurrent attacks, while many others who have a mutation in the HMBS gene never develop symptoms. The purpose of this research study is to learn more about genetic factors (specific patterns in a gene) that predispose or protect an individual with a change (or mutation) in the gene that causes Acute Intermittent Porphyria (AIP) to develop symptoms.

Committed to improving the quality of life of the porphyria patient community, relentlessly focused on advancing disease awareness, research, and therapies in all the porphyrias.