Acute Intermittent Porphyria
A rare inherited disorder causing sudden attacks of pain and nerve symptoms
Quick Facts
- Type: Inherited metabolic disorder
- Cause: A problem in heme production
- Hallmark: Attacks of severe abdominal pain
- Common triggers: Certain medications, fasting, hormones, stress
Overview
Acute intermittent porphyria (AIP) is a rare inherited disorder in the group of conditions called porphyrias. It is caused by a problem in one of the steps the body uses to make heme, a component of the oxygen-carrying protein in blood and other important molecules. When this step is impaired, substances called porphyrin precursors build up and can cause sudden episodes known as acute attacks.
Many people who carry the genetic change never have symptoms. Those who do experience attacks of severe abdominal pain along with nervous system and mental symptoms. Acute attacks can be serious and require prompt medical care. Between attacks, many people feel well, and avoiding known triggers greatly reduces the risk of further episodes.
Symptoms
Symptoms occur in attacks that can last days. The most common feature is severe abdominal pain. Other symptoms include:
- Severe, often poorly localized abdominal pain, sometimes with nausea, vomiting, and constipation
- Pain in the back, arms, or legs
- Muscle weakness, which in severe attacks can affect breathing
- Nervous system effects such as numbness, tingling, or seizures
- Mental symptoms such as anxiety, confusion, agitation, or hallucinations
- Reddish or dark urine
- A fast heartbeat and high blood pressure
Seek emergency care for severe abdominal pain with weakness, seizures, confusion, or difficulty breathing, as severe attacks can be dangerous.
Causes
AIP is caused by an inherited change in a gene involved in making heme. This reduces the activity of one enzyme in the heme pathway, allowing porphyrin precursors to accumulate during attacks. Most people inherit the condition from a parent, though not everyone with the gene develops symptoms.
Attacks are usually set off by triggers that increase the body's demand for heme, including:
- Certain medications: Many drugs can provoke attacks; people with AIP must check which medicines are safe.
- Fasting or low-calorie diets: Going without enough food.
- Hormonal changes: Such as those during the menstrual cycle.
- Alcohol, smoking, infections, and stress.
Risk Factors
- A family history of acute intermittent porphyria
- Being a carrier of the gene change
- Being a woman of reproductive age, as hormones can trigger attacks
- Use of medications known to provoke attacks
- Fasting, crash dieting, heavy alcohol use, smoking, infections, or significant stress
Diagnosis
AIP can be hard to diagnose because attacks mimic many other conditions. Testing during an attack is most informative:
- Urine tests: Measuring porphyrin precursors (such as PBG and ALA) in the urine during an attack; levels are typically high.
- Blood and stool tests: May be used to support the diagnosis and identify the type of porphyria.
- Genetic testing: Confirms the diagnosis and can identify affected family members.
Treatment
Treatment focuses on stopping acute attacks and preventing future ones:
- Treating acute attacks: Hospital care may include intravenous heme therapy, which helps switch off the overactive pathway, along with glucose, fluids, and medications for pain and nausea using drugs known to be safe in porphyria.
- Removing triggers: Stopping any triggering medication and treating underlying problems such as infection.
- Monitoring: Watching breathing, salts in the blood, and other functions during severe attacks.
- Preventive care: Avoiding known triggers and, for some people with frequent attacks, specialized preventive treatments.
Prevention
- Avoid medications known to trigger attacks; always check that any new medicine is safe in porphyria
- Eat regular, balanced meals and avoid fasting or crash diets
- Limit or avoid alcohol and do not smoke
- Manage stress and treat infections promptly
- Carry medical identification noting your diagnosis
- Inform all healthcare providers, including before any surgery, about your condition
When to See a Doctor
If you have been diagnosed with AIP, contact your healthcare team at the first signs of an attack. Seek emergency care for:
- Severe abdominal pain, especially with vomiting
- Muscle weakness or difficulty breathing
- Seizures, confusion, or severe agitation
- A very fast heartbeat or signs of dehydration
Anyone with unexplained recurrent severe abdominal pain and nerve or mental symptoms should be evaluated, and family members of someone with AIP may benefit from testing.
Frequently Asked Questions
What is acute intermittent porphyria?
It is a rare inherited disorder in which a step in making heme is impaired, allowing certain substances to build up and cause sudden attacks. Attacks typically feature severe abdominal pain along with nerve and mental symptoms. Many gene carriers never develop symptoms.
What triggers an attack?
Common triggers include certain medications, fasting or crash dieting, hormonal changes such as those in the menstrual cycle, alcohol, smoking, infections, and stress. Avoiding these triggers greatly reduces the risk of attacks.
What does a porphyria attack feel like?
An attack usually causes severe, often poorly localized abdominal pain, frequently with nausea, vomiting, and constipation. It can also cause back and limb pain, muscle weakness, numbness, seizures, anxiety or confusion, a fast heartbeat, and reddish or dark urine.
Is an attack dangerous?
It can be. Severe attacks may cause muscle weakness that affects breathing, seizures, or significant disturbances in the body's salts, so they need prompt hospital treatment. Seek emergency care for severe pain with weakness, breathing trouble, seizures, or confusion.
How is an attack treated?
Acute attacks are often treated in hospital with intravenous heme therapy, glucose, fluids, and medications for pain and nausea that are known to be safe in porphyria. Removing triggers and monitoring breathing and blood salts are also important parts of care.
References
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Porphyria.
- MedlinePlus, U.S. National Library of Medicine. Acute intermittent porphyria.
- American Porphyria Foundation.
- Genetic and Rare Diseases Information Center (GARD).