Acute and non-acute types
In the past, the porphyrias were divided into groups based on the site of the porphyrin production (hepatic or erythropoietic). Other clinicians classified them by whether there were effects on the person's skin or not (cutaneous porphyria).
Today, the porphyrias are usually divided into acute or non-acute types. Acute porphyrias produce attacks of pain and neurological effects which are severe and appear rapidly. Acute types include acute intermittent porphyria, ALAD-deficiency porphyria, variegate porphyria, and hereditary coproporphyria. The non-acute types are porphyria cutanea tarda, and hepatoerythopoietic and congenital erythropoietic porphyrias.
Acute intermittent porphyria (AIP) is the most severe kind of porphyria, with attacks developing over several hours or several days. Most individuals who inherit the gene for AIP never develop symptoms, and there are factors that are known to bring on attacks that susceptible people can avoid. Certain drugs, for example, are known to bring on or worsen attacks, as well as drinking alcohol, dieting, and hormonal changes. An attack often includes severe abdominal pain and constipation, and may include nausea, vomiting, pain in the back, arms, and legs, muscle weakness, and even rapid heartbeat, confusion, and seizures.
Many times a first attack of AIP may be misdiagnosed, and the medications given may just make things worse for the patient. Treatment should include a high calorie diet, although why this helps relieve an attack scientists aren't quite sure. Heme therapy can be administered intravenously. Symptoms usually resolve after an attack, but some patients develop nerve damage.
The other acute porphyrias have symptoms similar to AIP. ALAD-deficiency porphyria is extremely rare. In hereditary coproporphyria, skin photosensitivity may also be a symptom. Variegate porphyria is most common in the white population of South Africa, and it may also include skin symptoms as well as acute attacks.
Porphyria cutanea tarda (PCT), a non-acute disorder, is the most common of the porphyrias, and is acquired (develops in an individual from outside factors). Factors such as iron, alcohol, hepatitis C virus, estrogens (like in birth control pills), and possibly smoking, combine to cause an enzyme deficiency in the liver, leading to PCT.
"Cutanea" refers to the symptoms of PCT, which are on the skin. When exposed to the sun, the skin blisters, and the skin may thicken and darken. PCT is considered the most treatable porphyria. Once symptoms start to show, removing one pint of blood from the patient every one to two weeks (up to 5 or 6 pints of blood total) removes iron from the liver and offers relief. PCT usually does not recur after treatment.
Congenital erythropoietic porphyria (CEP), also known as Gunther's disease, is extremely rare. Unfortunately, its skin symptoms may be severe. Sun exposure may lead to blistering, scarring, and increased hair growth. Affected skin may harbor bacteria, and facial features and fingers may be lost through sun damage and infection. Hepatoerythropoietic porphyria is very rare, and similar to CEP in its symptoms of skin blistering.
A disorder related to the porphyrias is erythropoietic protoporphyria (EPP). In EPP, protoporphyrin accumulates in the bone marrow, red blood cells and sometimes the liver. Symptoms show on the skin after exposure to sunlight: swelling, burning, itching, and redness. Blistering and scarring are less common than in other porphyrias with skin symptoms.
Porphyria genes identified
Chromosome mapping in recent years has identified all the genes involved in the defective enzymes in the porphyrias. This means that DNA testing can identify people who carry one of these defective genes. Only a few laboratories in the world, however, currently do this type of testing. Prenatal diagnosis of congenital erythropoietic porphyria has been done, as well as successful gene therapy for both CEP and EPP. No doubt it will only be a matter of time before other successful therapies are developed, especially to relieve or prevent the acute porphyrias.
Information for this article was taken from:
- The American Porphyria Foundation
- Keung, Y-K, Chuahirun, T., & Cobos, E. (2000). Acute intermittent porphyria with seizure and paralysis in the puerperium. J Am Board Fam Pract, vol. 13, no. 1, 76-79.
- Lim, H. W.,& Cohen, J. L. (1999). The cutaneous porphyrias. Semin Cutan Med Surg, vol. 18, no. 4, 285-292.