Acute intermittent porphyria

[Tina]

Acute intermittent porphyria, which causes abdominal pain and neurologic symptoms, is the most common acute porphyria.

Many people never experience symptoms.
Symptoms may include vomiting, abdominal or back pain, weakness in arms or legs, and mental symptoms.
Laboratory tests are done on urine samples taken during the attack.
Maintaining good nutrition and avoiding alcohol and drugs that trigger attacks are important.
Attacks are treated by giving glucose and sometimes heme.

(See also Overview of Porphyrias.)
Acute intermittent porphyria occurs in people of all ethnic groups. In most countries, it is the most common of the acute porphyrias. Other acute porphyrias include

Variegate porphyria
Hereditary coproporphyria
Delta-aminolevulinic acid dehydratase-deficiency porphyria, which is extremely rare

Variegate porphyria and hereditary coproporphyria may also cause skin (cutaneous) symptoms.
Acute intermittent porphyria is due to a deficiency of the enzyme porphobilinogen deaminase (also known as hydroxymethylbilane synthase) that leads to accumulation of the porphyrin precursors delta-aminolevulinic acid and porphobilinogen initially in the liver.
The disorder is inherited due to a single abnormal gene from one parent. The normal gene from the other parent keeps the deficient enzyme at half-normal levels, which is sufficient to produce normal amounts of heme.
Most people with a deficiency of porphobilinogen deaminase never develop symptoms. In some people, however, certain factors can precipitate symptoms, causing an attack. Factors that can cause an acute porphyria attack include

Many drugs (including sex hormones, barbiturates, antiseizure drugs, and sulfonamide antibiotics)
Hormonal changes in women
Low-calorie, low-carbohydrate diet
Ingestion of alcohol
Exposure to organic solvents (for example, in dry cleaning fluids or paints)
Emotional stress
Infection and other illnesses
Surgery
Smoking

Usually a combination of factors is involved in causing an attack. Sometimes the factors that cause an attack cannot be identified.
Attacks are more common in women than in men and occur only very rarely before puberty. Very rarely, the disorder is inherited from both parents (and therefore two abnormal genes are present). Symptoms may then appear in childhood and include developmental abnormalities.