Acute intermittent porphyria (AIP)

What happens in this disease?

A change in the HMBS gene reduces an enzyme that makes heme. Heme is an important part of the protein in blood that carries oxygen. Some medicines, fasting, alcohol or hormone changes can trigger an attack. Then in-between substances build up in the liver and affect the nerves.

Which symptoms can occur?

Symptoms come in attacks. Attacks usually begin in a person's 20s or 30s and are more common in women. Most people are well between attacks.

• Severe, widespread belly pain (the most common symptom)
• Nausea, vomiting, constipation
• Dark or reddish urine
• Numbness in the arms and legs, muscle weakness
• Fast heartbeat and high blood pressure
• Anxiety, sleeplessness, changes in consciousness
• Seizures (fits)

How is it diagnosed?

This disease is considered in attacks of unexplained belly pain. During an attack, a substance called porphobilinogen is found to be high in the urine. Other tests tell the type apart. A genetic test helps screen family members.

Treatment and care

A severe attack is treated in hospital. Heme-containing treatment through a vein and sugar support are used. For adults who have frequent attacks, there is also an approved preventive treatment specific to the disease. Avoiding triggers is important. Before taking a new medicine, it should be checked whether it is safe. The doctor who follows the disease decides which treatment is suitable.

For the family: inheritance and genetic counselling

The disease is passed on through dominant inheritance. A parent who carries the gene has a 50 percent chance of passing it to each child. But most people who carry the gene never have an attack. Once a diagnosis is made in the family, genetic testing may be offered to relatives. Genetic counselling guides the family.