EPP: allergic to the sun

EPP is a hereditary metabolic disease that is not common in the Netherlands: only 200 cases are known. Another name for EPP is sun allergy. EPP members experience problems with their skin when it comes into contact with the sun. You don’t see much, but it hurts a lot. No medicines have yet been invented to cure it. However, there are remedies that patients use to reduce their complaints, such as ointments, protective clothing and filters.


EPP is the abbreviation for ‘erythropoietic protoporphyria’. The disease EPP occurs in approximately 200 people in the Netherlands and manifests itself at a young age. There is (yet) no treatment to cure this condition, but there are treatments that reduce and alleviate the symptoms. EPP is one of the less serious porphyrias, but the severity of the complaints varies per EPP. People with EPP use certain substances that lead to less sensitivity. They use filters that block out the purple sunlight, for example on their windows and car windows, and they use ointments. There are also anti-inflammatory preparations that can be used, but these medications have side effects. The consequences can be limited by reducing exposure to light. Protective clothing is also often used, EPP members often wear long sleeves, long trousers, gloves and a cap. Sunscreen doesn’t help. Sometimes even the circadian rhythm is reversed, so that the patient is awake at night and sleeps during the day. Light therapy with UVB can also help, because this therapy results in the thickening of the epidermis and thus visible light can penetrate less deeply through the skin.

Enzyme defect

If you have EPP, the enzyme ferrochelatase, which is responsible for the synthesis of the red blood dye, is not produced or is produced less in your body. This is the eighth step in the chain of reactions in which heme is produced. Haem is part of hemoglobin that binds an iron atom, namely the insertion of the iron atom into the protoporphyrin. This defect causes an accumulation of protoporphyrin, mainly in the skin and in red blood cells. When the sun falls on the molecules, the substance protoporphyrin, which is accumulated in the skin, reacts and the skin becomes inflamed and turns red. You usually see swelling and it often hurts. Besides the swelling and possible bruising, there is little visible on the skin. However, exposure of the skin to sunlight causes severe pain that can last for days. People with EPP are hypersensitive to the light of the sun, namely the violet and green part of the sunlight; and/or for certain artificial lighting. That is why the disease is also called sun allergy: EPPers are allergic to the sun.
It makes no difference whether EPP members live behind glass their entire lives, because glass does not block harmful rays. Sitting under a parasol is also of no use, because the light is only filtered and can still cause severe pain.


EPP is an inherited metabolic disease, but it is still unknown how the disease is inherited. It always skips a generation, so your aunt may have it and your own child may have it. Or a brother of your grandmother and yourself. It does not have to be the case that there is exactly one generation in between. If you have a parent with EPP, you can be a carrier yourself. Then it is possible that your child or your grandchild has it. It may also be that you are a carrier, but your child does not have EPP and is not a carrier. Then the line stops there. The inheritance of EPP is very erratic and only after research can you find out whether you are a carrier or not.



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