Erythropoietic protoporphyria (EPP) is a rare inherited disorder that causes the skin to become painful when exposed to sunlight.

In this article, we explore what EEP is, what symptoms it causes, and how to treat it. We also look at related conditions and describe when to see a doctor.

EEP occurs due to a deficiency of an enzyme called ferrochelatase. This causes a compound called protoporphyrin to accumulate in blood plasma, bone marrow, and red blood cells. The result is sensitivity to light, or photosensitivity.

EEP is one of eight inherited genetic disorders that are collectively called porphyria.

The American Porphyria Foundation estimate that EPP occurs in about 1 in 74,300 individuals.

There is currently no cure.

Some people with EEP have a gene called ALAS2. When this is the case, the health condition is called X-linked protoporphyria (XLP).

Symptoms typically develop in early infancy, after the first exposure to the sun.

The most common symptom is severe pain during exposure to sunlight, and the pain tends to affect the hands, feet, face, and ears more often.

Other symptoms include:

  • sensitivity to some artificial light sources
  • itching
  • tingling
  • a burning sensation
  • skin swelling, which may cause a rash
  • persistent skin inflammation

Rarely, a person with EEP develops skin blistering or discoloration, and the areas affected may thicken.

Symptoms tend to last as long as the light exposure, and they can be worse in summer and sunny climates.

The severity of the symptoms can vary. Some people can have hours of sun exposure before they experience pain, and for others, the pain begins within seconds.

A buildup of protoporphyrin can contribute to the formation of gallstones. People with EEP also have an increased risk of liver damage.

In a person with EEP, mutations in the FECH gene cause the body to have a deficiency of the enzyme ferrochelatase.

When there is not enough ferrochelatase, the body is unable to convert the compound protoporphyrin into heme, a molecule that enables blood to carry oxygen. As a result, protoporphyrin builds up in blood vessels under the skin.

Sunlight exposure activates the accumulated protoporphyrin, generating a reaction that leads to inflammation and severe pain.

EEP is an autosomal recessive disorder. This means that the biological parents of a person with EEP each carry one copy of the mutated FECH gene but display no symptoms of the condition.

There is no cure for EEP, but focusing on protection from the sun can help manage symptoms.

According to the British Skin Foundation, a charity, self-care methods include:

  • protective clothing, such as broad-brimmed hats, shirts with long sleeves, gloves, and trousers
  • reflecting sunscreens that contain titanium dioxide or zinc oxide
  • antihistamines, which may help people who develop a rash due to swelling

Because people with EEP are sensitive to visible light, sunscreens that protect from ultraviolet light are not effective.

Also, a doctor may recommend phototherapy — which does not trigger EEP pain — for 3 days over 6 weeks in the spring.

Phototherapy can help the skin to thicken and tan. The result may be better protection from the sun.

Further treatment methods may help. A doctor may, for example, prescribe beta carotene capsules. Though no research supports this approach, anecdotal evidence suggests that it can improve symptoms.

Also, people who avoid sunlight may benefit from vitamin D supplements.

The genetic mutation responsible for EEP can lead to other issues.

Liver disease

Liver disease develops in 1–4% of people with EEP, and liver failure occurs in 2–5% of this group. This results from the excess protoporphyrin accumulating in the liver.

A person with EPP and liver disease may require treatment from a specialist and a liver or bone marrow transplant.

People with EPP should avoid alcohol and other substances that could damage the liver.


Gallstones are common among people with EPP. According to an older medical article, from 2009, 20% of people with EEP develop gallstones.


According to a 2019 review, anemia occurs in about 47% of people with EPP.

Early diagnosis of EPP is crucial, as the symptoms tend to appear soon after birth.

If an infant shows any signs of sensitivity to sunlight, such as crying when outdoors or in the car, consult a medical professional.

For people with EPP, caring for mental and emotional health is very important. A 2019 study involving people in North America with EPP or XLP confirmed that these conditions can have a considerable impact on the quality of life.

EEP is a rare genetic condition that causes pain in response to sunlight exposure.

The pain and other symptoms vary in severity and duration from person to person, and some also experience sensitivity in response to artificial light.

While EEP can affect the quality of life, treatments are available. It is crucial to receive expert medical advice.