Frequently Asked Questions About the Porphyrias

The best way to classify a case of porphyria is to determine which enzyme is deficient, or not functioning properly. Normally these enzymes act in a sequence to make heme from simpler molecules. Heme is a vital substance for all body organs and consists of an iron atom surrounded by a porphyrin molecule. If a specific enzyme is not made properly or there is not enough of the enzyme, it cannot function properly and that step in the heme-making process cannot proceed.

Sometimes other classifications are useful. Most commonly the porphyrias are divided into the “acute“ and “cutaneous” porphyrias, depending on the primary symptoms. The acute porphyrias [acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), variegate porphyria (VP), and ALA-dehydratase deficiency porphyria (ALD)] present with sudden attacks of severe stomach pain that last for several days; VP and HCP may also have skin symptoms of blistering after sun exposure. The cutaneous porphyrias present with blistering and scarring of the skin, pain, and/or redness and swelling in sun-exposed areas. The porphyrias may also be classified as “hepatic” or “erythropoietic”, depending on the organ where the porphyrins accumulate, the liver for the hepatic porphyrias [AIP, HCP, VP, porphyria cutanea tarda (PCT), and hepatoerythropoietic porphyria (HEP)] or the bone marrow for the erythropoietic porphyrias [congenital crythropoietic porphyria (CEP), erythropoietic protoporphyria (EPP), and x-linked protoporphyria (XLP)].

No, there are many laboratory tests available for the porphyrias, and the right tests to order depend on the type of porphyria the doctor suspects. It is often difficult to decide which tests should be chosen, and the results may be difficult to interpret. The tests vary in sensitivity and specificity. If a test is “sensitive”, it is unlikely to be falsely negative (that is, fail to diagnose porphyria in a patient who has the disorder). If a test is “specific,” it is unlikely to be falsely positive (that is, diagnose porphyria in a patient who does not have the disorder). Certain tests are both sensitive and specific in patients who have symptoms that are suggestive of a porphyria. It is advisable to have the testing performed by a laboratory that has expertise in the clinical aspects of porphyria and can provide a valid interpretation of the test results. If testing has been performed in laboratories other than porphyria laboratories, consultation with a porphyria expert is advised before a final diagnosis is made.

When abdominal and neurological symptoms suggest an acute porphyria, the best screening tests are urinary aminolevulinic acid (ALA) and porphobilinogen (PBG). When there are cutaneous symptoms that suggest porphyria, the best screening test is a plasma porphyrin assay. If one of these screening tests is abnormal, more extensive testing, including urinary, fecal, and red blood cell porphyrins, are often indicated. Urinary, fecal, and red blood cell porphyrin measurements are not very useful for initial screening because they lack either sensitivity or specificity and, therefore, are often difficult to interpret. Measurement of heme biosynthetic enzymes in red blood cells or lymphocytes is not appropriate for screening unless it is part of a family study that is done after someone in the family is already known to have a specific enzyme deficiency. The table below summarizes the tests to be done for each type of porphyria.

**The Mount Sinai Lab only tests for urine PBG

NOTE—To diagnose all of the porphyrias GENETIC TESTING is also recommended. Information on genetic testing can be found at: http://icahn.mssm.edu/departments-and-institutes/genomics/genetic-testing/test-catalog.

However, many patients have not had an acute attack or are not symptomatic at present, so biochemical testing may be inconclusive. In contrast, DNA testing is the most accurate and reliable method for determining if a person has a specific porphyria and is considered the "gold standard" for the diagnosis of genetic disorders. If a mutation (or change) in the DNA sequence is found in a specific porphyria-causing gene, the diagnosis of that porphyria is confirmed. DNA analysis will detect more than 97% of known disease-causing mutations. DNA testing can be performed whether the patient is symptomatic or not. Once a mutation has been identified, DNA analysis can then be performed on other family members to determine if they have inherited that porphyria, thus allowing identification of individuals who can be counseled about appropriate management in order to avoid or minimize disease complications.

There are several Porphyria experts in the US and outside the US, including the Porphyria Centers in this Consortium. Information about other experts can be obtained by contacting one of the Porphyrias Consortium members. If a porphyria is suspected, any physician can order the appropriate tests. Since interpretation of these results may be difficult, it is best for the physician or healthcare professional to consult with a porphyria expert for an accurate interpretation of the results and, if necessary, advice about additional testing, treatment, or prevention and precautionary measures.

Because all porphyrias are uncommon, it is very unlikely that more than one type of porphyria will occur in the same family, or that a person with one type of porphyria will go on to develop another type. However, patients with more than one type of porphyria have been reported.

The liver is affected differently for each type of porphyria. Please refer to the disorder definitions page about your type of porphyria for more information on how the liver is involved. Although the different types of porphyria affect the liver different, liver function tests should be performed routinely (usually annually) on all individuals diagnosed with any type of porphyria.

Such a situation needs to be dealt with on an individual basis. Whether further testing is recommended depends on how the patient was initially diagnosed and how the porphyria expert made the decision that porphyria is not the diagnosis. The results of biochemical testing are sometimes interpreted incorrectly by a physician who is not an expert in porphyria. Review of the results of the biochemical testing by a porphyria expert may determine that the results are not consistent with what is typically seen in a patient with porphyria during an attack. The results of DNA analysis may also contribute to the porphyria expert saying that it is unlikely that the patient has porphyria. DNA analysis, although considered to be the “gold standard” for diagnosis, is not perfect in that the patient may have a mutation in a part of the porphyria gene that is not analyzed by routine testing or the patient has a mutation in a porphyria gene that was not analyzed. In the event that a diagnosis of porphyria is still suspect, then it is recommended that the patient undergo additional biochemical testing at the time of an acute attack. Additionally, further testing may include DNA analysis for other acute porphyrias (if only one or two were tested).

Yes we are conducting research about the porphyrias. For additional information about our studies and how to volunteer to participate, please contact either the Porphyrias Consortium Project Managers (mary.freeman@mssm.edu and cristoforo.terrasi@mssm.edu) or a participating clinical center coordinator closest to you (see list of Porphyrias Consortium participating clinical centers for locations and contact information).

Yes! The diagnosis of porphyria is always an important item of medical information, even when there are no symptoms. It may, for example, influence the choice of drugs to treat other conditions, the choice of anesthesia for surgery, or dietary recommendations.

Surgery and pregnancy may increase the risk of an acute porphyria attack. This risk can be greatly reduced if certain precautions are taken, including the type of anesthesia used in surgeries. The patient’s surgeon and anesthesiologist should consult a porphyria expert prior to hospitalization for surgery. Such consultation may also be helpful during pregnancy. Although attacks of acute porphyria can occur during pregnancy, the risk appears to be less than formally thought. Treatment of acute attacks during pregnancy is also possible.

For information about safe and unsafe drugs in the acute porphyrias, visit the United Porphyrias Association website for access to and instructions for using an online drug database. The database contains expert assessments of the potential of drugs to provoke attacks of acute porphyria (AIP, VP, HCP & ADP) based on the available evidence. However, this evidence is not always complete, which may lead to some degree of uncertainty. The information in these databases is meant as guidance to health care professionals. It must be made clear that the prescription of drugs to a patient with acute porphyria is entirely at the risk of the physician in charge.

Since most commonly used drugs have not been tested, they should be avoided if at all possible. If a question regarding drug safety arises, a physician or medical center specializing in porphyria should be contacted.

Yes. Since the acute porphyrias are inherited in an autosomal dominant pattern, males and females are equally at risk for having an acute porphyria. Exposure to certain environmental factors, such as drugs, chemicals, and diet, greatly influence whether an individual - males and females - with a mutation in a porphyria-causing gene has symptoms and the severity of symptoms. However, one of the environmental factors is hormones, and, therefore, acute attacks are more common in women than in men. Women may experience cyclical acute attacks associated with their menstrual cycle, starting in puberty. Such attacks in women may occur after ovulation and during the last part of the menstrual cycle when progesterone levels are high.

Patients with an acute porphyria should have a healthy balanced diet. Fasting for long periods of time and dieting should be avoided.

Generally, the acute porphyrias do not affect thinking and memory long term; these can be affected when someone is having an acute attack. Someone with acute porphyria may also experience some neurological effects, including confusion, convulsions, muscle weakness, and, rarely, paralysis, due to effects on the nervous system from an acute attack.

In an individual with an acute porphyria, an acute attack can be brought on by certain drugs, hormones in women, environmental factors including chemicals of various types, nutrition including fasting and low carbohydrate diets, alcoholic beverages, medical and physical stress, and physical fatigue. Many times the trigger of an acute attack is unknown.

Flu shots are not contraindicated for individuals diagnosed with acute porphyria, and can be taken safely. Any immunizations appear to be okay. In fact, since other illnesses can bring on an acute attack, remaining healthy is one of the most important ways to prevent acute attacks.

There has been no information to date to suggest that CAT scans with or without contrast agents should not be performed on an individual with acute porphyria.

Organ donation would be up to a particular transplant program or network. In acute porphyrias any organ should be acceptable except the liver. A person with an acute porphyria should not donate their liver.

Drugs on the “unsafe” list are those drugs that should be avoided by individuals diagnosed with an acute porphyria because they have been found to provoke an acute attack in some individuals. If a drug prescribed for an individual diagnosed with an acute porphyria is on the “unsafe” list, the prescribing physician should check the Drug Database for a safe alternative. No drug should be withheld if it is judged essential for optimum treatment of a life-threatening condition (e.g. chemotherapy for cancer). The risk versus the benefit should be assessed and discussed with the patient. For help with this assessment you may wish to contact a Porphyria expert. It may be recommended that a patient undergo biochemical monitoring in the early stages of treatment. It must also be noted that response to drugs in patients with an acute porphyria is extremely variable and individuals may be encountered who have used an unsafe drug without adverse effect.

Most patients with a cutaneous type of porphyria must learn to avoid sunlight as much as possible. Protective clothing may also be recommended. For patients with EPP, treatment with pharmaceutical-grade β-carotene (Lumitene, Tishcon) or cysteine may improve sunlight tolerance but does not lower porphyrin levels. Over-the-counter sunscreens and over-the-counter beta carotene (vitamin A) is not effective.