Acute Intermittent Porphyria (AIP)

What is acute intermittent porphyria?

Acute intermittent porphyria (AIP) is a rare metabolic disorder that belongs to the larger group of porphyrias. Specifically, AIP is an acute, hepatic form of porphyria. A lack of the hydroxymethylbilane synthase enzyme combined with environmental factors leads to the characteristic symptoms of this disorder, which appear in the form of episodes.

What are the symptoms of acute intermittent porphyria?

Symptoms range widely in severity and course. They typically appear in attacks or episodes that can last from a few hours to a few days, stemming from a variety of triggers. Not every affected individual experiences every symptom, but possible effects include:

Abdominal pain
Pain in the legs, arms, neck, lower back, and/or buttocks
Nausea/vomiting
Diarrhea
Constipation
Blockage of the small intestine
Difficulty urinating
Peripheral neuropathy
Muscle weakness
- This can lead to impaired motor function
High blood pressure
Seizures
Rapid heart rate
Psychological symptoms
- These include hallucinations, insomnia, paranoia, irritability, depression, disorientation, anxiety, and altered consciousness

It is important to seek treatment for this condition, as possible complications include kidney damage with the potential to progress to kidney failure, hypertension, cholangiocarcinoma, hepatocellular carcinoma, or other liver cancers.

What causes acute intermittent porphyria?

Numerous factors play a role in the cause of AIP. Firstly, affected individuals have a mutated HMBS gene which is inherited in an autosomal dominant pattern. This altered gene leads to a deficiency of the hydroxymethylbilane synthase enzyme, which then affects the heme biosynthesis process.

However, this genetic mutation alone is not enough to cause AIP. Environmental factors trigger the symptoms, which appear in episodes. These triggers are thought to impact heme production in the liver. They include stress, certain drugs, restricting calories, excessive alcohol consumption, certain hormonal factors, infections, and any combination of these options.

How is acute intermittent porphyria diagnosed?

Diagnosis of this condition can be very difficult, as symptoms vary widely and are not always present. Testing includes urinary tests for PBG and delta-ALA excretion. Genetic testing can be used to confirm but is not necessary.

What are the treatments for acute intermittent porphyria?

Treatment is intended to address specific symptoms, prevent complications, and decrease heme production in the liver. Avoiding triggers is also essential for treatment. Medications used to treat AIP include Panhematin, Givlaari, and Normosang. Otherwise, doctors will work to treat specific symptoms as they appear. This may require hospitalization during an attack.