Porphyria and Seizures
An estimated 10 to 20% of people with acute porphyria experience seizures, which can be life-changing and lead to many complications.
What is porphyria?
Porphyria is a group of genetic disorders that all result from the dysfunction of the metabolic pathway that produces heme. Heme is an integral part of hemoglobin, the molecule in red blood cells that carries oxygen. Mutations in the genes that provide instructions for making the enzymes that convert heme precursors — called porphyrins — into heme result in low amounts of heme along with a buildup of porphyrins. Depending on the type, these porphyrins can predominantly affect the skin (causing cutaneous porphyria) or the nervous system (causing acute porphyria).
What are seizures?
Seizures are periods of abnormal electrical activity in the brain. They can come in several different forms depending on which parts of the brain they affect and to what degree.
Seizures that are widespread and affect multiple parts of the brain are called generalized seizures. They can result in rhythmic movements (clonic), jerking or twisting motions (myoclonic), or periods of staring with no response (absence). They also can cause muscles to stiffen (tonic) or go limp causing patients to fall to the ground (atonic). The most widely-known type of seizure involves whole-body convulsions with a loss of consciousness — a tonic-clonic seizure.
Localized seizures, also known as focal seizures, affect a smaller portion of the brain. They can lead to altered consciousness and result in changes in a person’s senses or emotions. They also may cause a loss of consciousness or awareness. This usually is accompanied by repetitive movements such as hand rubbing, chewing or walking in circles.
How porphyria may cause seizures
The exact link between porphyria and seizures is not clear. However, in an increasing number of patients, they seem to be related to posterior reversible encephalopathy syndrome (PRES). PRES is a disorder usually caused by increased pressure on the brain from high blood pressure and swelling. The increased pressure can damage brain cells and lead to symptoms such as headaches, visual disturbances, altered consciousness, and seizures.
Patients experiencing an acute porphyria attack often have low levels of sodium in their blood. Sodium is integral to nerve cell signaling and low levels can lead to dysfunction in the communication between nerve cells and lead to seizures.
Seizures in porphyria sometimes can be difficult to manage since several seizure medications may cause or worsen acute porphyria attacks.
For seizures that occur during an acute porphyria attack, patients should be given a single shot of an intravenous benzodiazepine to try to stop the seizures. Once the seizure has ended or is under control, the porphyria attack can be treated with an IV containing high levels of sugar or a dose of hematin (a heme-containing compound). Hematin can help inhibit the body’s attempts to make more heme, shutting down the heme production pathway and reducing the symptoms of an acute attack.
Once the initial seizure has stopped, it is important to try to figure out the possible cause of the seizure such as PRES, or an electrolyte imbalance like low sodium levels. Doctors may treat PRES with medication to reduce blood pressure. They can treat electrolyte imbalances through fluid restriction or administration of a saline (salt) solution. Controlling porphyria attacks also may help prevent seizures.
Last updated: Dec. 15, 2020
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