With the advent of the new Midnight Sun movie released in theaters last week, I thought it might be helpful to give my understanding of some of the differences between Xeroderma Pigmentosum (abbreviated as XP) and the condition that I have, Erythropoietic Protoporphyria (abbreviated as EPP).

I have not yet seen the movie Midnight Sun and this is by no means an endorsement. I haven’t read a synopsis on the plot, though I know it’s a romantic movie about a girl with XP. I tend to veer towards action-packed movies over chick-flicks.

I am no medical expert on comparing these two conditions, so if anything I say is wrong please let me know and I will correct it posthaste.

Now that my disclaimers are out of the way, what are some differences and similarities between these two rare conditions?

Skin-Deep Similarity

People with both conditions share similarities in that they cannot be exposed to sunlight and that there is no standard medical treatment for either. However, that is about where the similarities end. Symptoms, genetics, degrees of sensitivity, and consequences of exposure surrounding these two respective diseases are all different.


They are both very rare. It is estimated that 1 in 1 million people have XP in the United States, which, if you do the math, comes out to around 300-400 people. I’m not exactly sure how many are “on the books,” so to speak.

EPP is estimated to affect roughly 1 in 200,000 people in the US, though there are only about 500-600 people “on the books” of the APF database.

In Pop Culture

Despite EPP being slightly more common, more people have heard of XP. There are a few films other than Midnight Sun that surround XP. These include titles such as Dark Side of the Sun (1988) starring Brad Pitt, and the CBS television movie Children of the Dark (1994). There are other movies and TV shows that feature briefly characters with XP, and there is the relatively successful Midnight Bay Trilogy novel series by Dean Koontz, where the main protagonist has XP.

I know of no references to EPP in pop culture, other than obscure mentions.


There is good reason for XP’s infamy. XP is fatal unless patients take restrictive precautions, and many worldwide do not live long into adulthood. (Thus it makes for a suspenseful plot hook for writers and producers.)

EPP is not necessarily fatal, though it has been known to cause dangerous liver complications especially in conjunction with alcohol consumption.

Electromagnetic Spectrum

Those with XP are unable to be exposed to ultraviolet light (100nm-400nm) from basically any source, though the sun is the biggest worry and tolerance varies.

Those with EPP are unable to be exposed to varying intensities of visible blue light (350nm-500nm) from the sunlight and certain artificial light sources, specific to the individual.

External Symptoms

Visible symptoms of XP can include pain, tumors, cancerous skin lesions, and large incidences of freckles following exposure to sunlight.

Symptoms of EPP are not always visible, though “invisible” pain should be expected with the potential for mild swelling or discoloration.

Internal Symptoms

There are also invisible symptoms of XP, which include cancer, genetic damage, and other symptoms that are not usually associated with ultraviolet exposure. People with XP have a very limited ability to filter out ultraviolet light to their organs and cells.

Visible light causes a chemical reaction within people who have EPP, which releases into the skin in the form of an agitated, energetic toxin that irritates the nerve cells. These toxins can increase the strain on the liver.


Obviously, XP is by far the more severe of the two conditions. Both conditions are life-altering for everyone involved in ways that those on the outside looking in can’t quite understand.

Obtaining a Diagnosis

Most doctors and medical specialists know very little about either EPP or XP. Finding good information for patients can be very difficult, especially for those who haven’t been officially diagnosed. Doctors aren’t all-knowing. Often, families obtain a correct diagnosis by performing their own research and then telling the doctor which tests to perform.

Where to Find More Information


The best source of information for Xeroderma Pigmentosum that I know of is the Xeroderma Pigmentosum Society, at xps.org.


The best source of information for Erythropoietic Protoporphyria that I know of is the American Porphyria Foundation, at porphyriafoundation.com.

Though I haven’t seen the movie and can’t comment on its quality, I’d like to thank the producers of Midnight Sun for bringing more awareness of this condition to our society at large. Awareness helps reduce needless suffering in some who struggle to find a diagnosis. It also indirectly increases funding of research towards finding treatment or even, dare I hope, a cure for rare conditions like XP and EPP.

6 thoughts on “EPP vs XP

  1. I also have EPP and I saw the movie with my husband and kids. Chick flick aside, I certainly could relate to the life style, the isolation and the pain. I left the theater feeling lucky for my 5-10 minutes of light.


    1. My older brother and my youngest sister have EPP. People really don’t understand this at all, so happy its being talked about. Also sure is nice to know about others , I grew up without this disease but still lived with it , wasn’t easy for the family either. Still is very sad to know my siblings can’t do a lot that people take for granite


      1. Dj,
        Thank you for taking the time to leave a comment and for speaking up for your siblings.
        You never know who will be affected as you relate your family’s experiences. You may or may not know someone else with EPP now, but the people you talk to may remember you if they make a friend who is struggling to find a diagnosis.
        “Your son cries when he goes outside?” they may ask their friend. “Well, I knew this one person whose brother and sister had this rare sun condition…”
        You could help save a child from years of painful exposure just with simple conversation.


    2. Ginger,
      Thank you for sharing your thoughts.
      Raising a family when you have EPP is a challenge that I haven’t quite come to terms with yet. I have two young children who are my favorite people in the world.


  2. My older brother has EPP, and I feel like I have a very, very slight version of it as I do get swelling hands on a much smaller scale as my brother. Even if I am just paranoid, and I don’t actually have it, it still affects mine and my family’s life. Everything from vacation to the ways of my brother dressing are different due to EPP. I’m hoping for a cure for my brother’s sake, as well with everyone else suffering from XP or EPP


    1. Carrie,
      Thank you for sharing.
      As I understand it, there are varying thresholds of sensitivity. I am on the moderate to severe sensitivity scale, but I know some people with EPP who can be outside for up to an hour without issues.
      If you’re questioning whether or not you have EPP, you can get a genetic test that is more reliable than the blood test. My bloodwork was always conclusive, but the genetic test definitely put my mind completely at ease that it isn’t just in my head.
      If you’re interested in knowing more about potential treatments, there is information at the American Porphyria Foundation website on some up and coming medicines and therapies.
      Wishing you the best,


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