| Acute intermittent porphyria is inherited as an autosomal dominant disorder and is characterized by recurrent attacks of abdominal pain, gastrointestinal dysfunction, neurologic disturbances, and excessive amounts of aminolevulinic acid and porphobilinogen in the urine. Acute intermittent porphyria is the most common and the most severe form of acute hepatic porphyria. It results from lower than normal levels (less than 50%) of porphobilinogen (PBG) deaminase that leads to accumulation of the heme precursors deltaaminolevulinic acid and porphobilinogen. Many drugs can bring on an attack. Hormones, such as progesterone and related steroids, can precipitate symptoms, as can low-calorie and low-carbohydrate diets, large amounts of alcohol, or smoking. Stress resulting from an infection, another illness, surgery, or a psychologic upset is also some-times implicated. Usually a combination of factors is involved. Sometimes the factors that cause an attack cannot be identified. |