One of a variety of hereditary diseases that are characterized by abnormalities in the reactions needed for the production of heme, an essential substance for the body, resulting in increased formation and excretion of chemicals called porphyrins. Most porphyrias affect the skin or the nervous system. Attacks may range from mild to severe. Besides having abdominal and nerve pain, the patient may suffer rapid heartbeat, mania, muscle cramps, muscle weakness, breathing problems, hallucinations, and coma. Acute attacks are often precipitated by the use of certain drugs, such as barbiturates, sulphonamides, and birth control pills; alcohol use; hormonal changes during menstruation or pregnancy; dieting or fasting; and infections. One type of porphyria, acute intermittent porphyria, may have affected members of the House of Hanover in England, including ‘Mad’ King George, who may have suffered attacks of porphyria instead of being ‘mad.’
- Porphyria cutanea tarda
The familial form of porphyria cutanea tarda — is inherited as an autosomal dominant trait with males and females affected in multiple generations. The enzyme UROD is reduced in all tissues. The sporadic form of porphyria cutanea tarda — is more common. The enzyme UROD is only reduced in the liver. It appears sporadically in […]
- Port wine stain
A mark on the skin that resembles port wine (porto) in its rich ruby red color. Due to an abnormal aggregation of capillaries, a port wine stain is a type of vascular malformation (vascular birthmark). A port wine stain on the face is a sign of the Sturge-Weber syndrome.
- Portable generator safety
Read and observe the instructions from the generator manufacturer for safe operation before hooking up the generator. Generators emit carbon monoxide. Always run the generator outdoors in a well-ventilated area. Do not run a generator in an enclosed area. Use the generator outdoors only (as indicated above) away from open windows, vents or doors. Deadly […]
- Portal vein
A large vein formed by the union of the splenic and superior mesenteric veins. The portal vein conveys venous blood to the liver for detoxification before the blood is returned to circulation via the hepatic veins.
- Positional cloning
Cloning a gene based simply on knowing its position in the genome without any idea of the function of that gene. Because this is the reverse of how things have been traditionally done, it has also been called reverse genetics.