Porphyria

Porphyrias are a group of genetic disorders caused by problems with how your body makes a substance called heme. Heme is found throughout the body, especially in your blood and bone marrow, where it carries oxygen.

Porphyrias affect the skin or the nervous system. People with the skin type develop blisters, itching, and swelling of their skin when it is exposed to sunlight. The nervous system type is called acute porphyria. Symptoms include pain in the chest or abdomen, vomiting, and diarrhea or constipation. During an attack, symptoms can include muscle numbness, tingling, paralysis, cramping, and personality or mental changes. Certain triggers can cause an attack, including some medicines, smoking, drinking alcohol, infections, stress and sun exposure. Attacks develop over hours or days. They can last for days or weeks.

Porphyria can be hard to diagnose. It requires blood, urine and stool tests. Each type has a different treatment. It usually involves medicine, treatment with heme or drawing blood.

National Institute of Diabetes and Digestive and Kidney Diseases

Porphyria on Wikipedia

The '''porphyrias''' are inherited or acquired disorders of certain enzymes in the heme biosynthetic pathway (also called porphyrin pathway). They are broadly classified as '''hepatic porphyrias''' or '''erythropoietic porphyrias''', based on the site of the overproduction and mainly accumulation of the porphyrins (or their chemical precursors).

Overview

In humans, porphyrins are the main precursors of heme, an essential constituent of hemoglobin, myoglobin and cytochrome. Deficiency in the enzymes of the porphyrin pathway leads to insufficient production of heme. This is, however, not the main problem; most enzymes - even when less functional - have enough residual activity to assist in heme biosynthesis. The largest problem in these deficiencies is the accumulation of porphyrins, the heme precursors, which are toxic to tissue in high concentrations. The chemical properties of these intermediates determine in which tissue they accumulate, whether they are photosensitive, and how the compound is excreted (in the urine or feces).

Subtypes

There are eight enzymes in the heme biosynthetic pathway: the first and the last three are in the mitochondria, while the other four are in the cytosol. # δ-aminolevulinate (ALA) synthase # δ-aminolevulinate (ALA) dehydratase # hydroxymethylbilane (HMB) synthase # uroporphyrinogen (URO) synthase # uroporphyrinogen (URO) decarboxylase # coproporphyrinogen (COPRO) oxidase # protoporphyrinogen (PROTO) oxidase # ferrochelastase

Hepatic porphyria

The hepatic porphyrias include: * ALA dehydratase deficiency * acute intermittent porphyria (AIP): a deficiency in HMB synthase * hereditary coproporphyria (HCP): a deficiency in COPRO oxidase * variegate porphyria (VP): a deficiency in PROTO oxidase * porphyria cutanea tarda (PCT): a deficiency in URO decarboxylase

Erythropoetic porphyria

The erythropoetic porphyrias include: * X-linked sideroblastic ... [ Read More ]

External Resources

Porphyria's Lover by Scott McCloud - Psychedelic online comic strip adaptation of Browning's poem.

Amanita porphyria - image and poisoning information (German). [Giftinformationszentrale Bonn - Porphyrbrauner Wulstling (Amanita porphyria).]

The Merck Manual: Endocrine and Metabolic Disorders - Chapters on a variety of endocrine problems such as hyperlipidemia, polyglandular deficiency syndromes, the porphyrias, amyloidosis, and others.

Porphyria Page - A patient guide for all people with this disorder. Compiled by Professor Michael Moore.

The American Porphyria Foundation - Non-profit organization advancing awareness, research, and treatment of Porphyria. Fact sheets and links to related resources.

Porphyrias: Diagnosis and Treatment - Clinical manifestations, diagnosis, etiology and treatment of six types of porphyrias are discussed.

King George II and Porphyria - Talks about the symptoms of porphyria affecting King George III who ruled England during the American revolution.

Canadian Porphyria Foundation - Mission statement, objectives of the organization, newsletters and safe and unsafe drugs. Also: A Guide to Porphyria - a complete booklet of information.

Diagnosing the Porphyrias - An article by Thomas G. DeLoughery, Associate Professor of Medicine.

Porphyria: The Unknown Disease - Genetic metabolic disorder. Overview of types, testing and diagnosis, and links.