The porphyrias are a group of rare diseases that cause problems in the skin and nervous system. Porphyrias occur when the body accumulates too many porphyrins.
Usually, your body makes a small amount of porphyrins when it produces heme. Heme is an important component of hemoglobin, the protein in red blood cells that carries oxygen. Heme production is a multi-step process and a different enzyme controls each step. If one of these enzymes is defective, this can cause porphyrins to build up in your body and potentially reach toxic levels. This causes porphyria.
Porphyria is rare, and most types of porphyria are transmitted genetically. Although genes cause the defective enzymes that contribute to porphyria, certain environmental factors, underlying medical conditions, and lifestyle choices can precipitate the onset of disease symptoms. These factors include:
- sun exposure
- hepatitis C
- medications, including birth control and barbiturates
- consumption of alcohol or drugs
- crash diets
- psychological stress
- stress caused by infection, surgery, or accidents
Porphyrias affect the skin and/or nervous system. There are seven different forms of this disease, and each is associated with a deficiency of a different enzyme in the production of heme. The types of porphyria are:
- porphyria cutanea tarda (PCT), also called cutaneous porphyria: This type of porphryia sometimes runs in families, but it can also appear at random. It is the most common form of porphyria, and it affects the skin. It causes fluid-filled blisters in areas of the skin exposed to sunlight. People with this form of porphyria are unusually sensitive to light. With short-term sun exposure, they develop rashes and blisters. With long-term exposure, they develop scars and skin discoloration. The most common risk factor for PCT is heavy alcohol consumption.
- acute intermittent porphyria (AIP), also called porphyria hepatica: An inherited type of porphyria, AIP affects the neurological system. Symptoms include abdominal pain, muscle weakness, confusion, seizures, palpitations, and high blood pressure, diarrhea, and constipation.
- erythropoietic protoporphyria (EPP): Also inherited, EPP affects the skin. It causes patients to become extra sensitive to sunlight. Patients with EPP often develop itching, burning, redness, pain, and swelling upon even brief sun exposure. In rare cases, affected patients can develop gallstones and liver disease.
- congenital erythropoietic protoporphyria: This condition, also genetic, causes a number of abnormalities. Patients may experience pinkish urine, fragile skin, anemia, spleen enlargement, and reddish-brown teeth and bones.
- variegate porphyria (VP): This condition, also inherited, primarily affects the skin. VP causes chronic skin lesions that heal slowly. In some cases, the condition can also cause some of the neurological symptoms associated with AIP.
- hereditary coproporphyria: This genetic condition, like VP, can affect both the skin and the neurological system, causing the type of symptoms associated with both PCT and AIP.
- acquired hepatic porphyria: This rare condition is not genetic. Rather, it is caused by intoxications. Like herediary coprophyria, it can affect both the skin and the neurological system.
Doctors can diagnose the different forms of porphyria using urine, blood, and fecal tests. Once diagnosed, it’s possible to take precautions to prevent symptoms from occurring. Lab tests can also help monitor these conditions.
Urine may be collected in either a random, single sample or over the course of a 24-hour period. However, the production and elimination of porphyrins may vary throughout the day, so a random sample may miss elevated porphyrin levels.
According to Lab Tests Online, a 24-hour collection gives the most accurate picture of a person’s porphyrin levels.
A 24-hour urine test is painless and only involves ordinary urination.
Here is how the collection procedure works:
- On day one, you will urinate into the toilet upon rising in the morning. Flush this first sample away.
- For the rest of the day, you will collect all of your urine in a special container and store it in a cool place.
- On day two, you will urinate into the special container upon rising in the morning.
- After that, you will return the container to the lab as soon as possible.
If you are the parent of an infant who is taking the urine test, you will need to follow the following procedure:
- On day one, you will need to wash the area around the baby’s urethra, then attach a collection bag to that area. For a boy, you will place the bag over his penis. For a girl, you will place the bag over her labia. You can then put the baby’s diaper on over the bag.
- Over the rest of the 24-hour period, you will collect samples according to the same schedule as adults.
- Throughout the day, check the bag. You will need to change the bag each time the baby has urinated.
- Each time the baby has urinated, pour the sample into the collection container. Keep this container in a cool place.
- On day two, collect the final sample when the baby first wakes up.
- Return the container to the lab as soon as possible.
Parents of infants taking the test may wish to have extra collection bags available in case an active baby dislodges the bag.
If you are an adult taking the test, your healthcare provider may instruct you to stop taking drugs that could interfere with the accuracy of the porphyrins urine test. However, do this under only your doctor’s guidance and according to his or her instructions.
According to the National Institutes of Health, the following drugs may interfere with an accurate measurement of porphyrins in the urine:
- aminosalicylic acid
- birth control pills
- chloral hydrate
- sulfonamides (NIH 2)
The normal range for a 24-hour porphyrins urine test is about 50 to 300 mg (milligrams), although results vary slightly in different laboratories.
Abnormal test results can indicate liver cancer, hepatitis, lead poisoning, or one of the different forms of porphyria. Your doctor will be able to interpret the results for a diagnosis and recommend the best course of treatment.