I examined a 53 year-old woman this morning with a mild facial eruption that at best was slightly erythematous and papular. She had been out in the sun a few days ago; apparently this has happened periodically over the last few years. I started to think about the usual suspects (contact, photocontact, doubtfully lupus) and asked her about any systemic manifestations. At that point she said “Do you think my diagnosis of porphyria has something to do with this?” I asked her if she was going to keep that a secret! Apparently she was diagnosed with EPP as a child – she has been on betacarotene since, and was considered to have a mild case. Indeed, other than her minimal rash, there were no classical findings of furrow-like scars, pebbling, or keratoderma. The patient acknowledged that her manifestations were that she would get red and be very uncomfortable in the sun. Today, we discussed strict sun avoidance, beta-carotene, and making sure that she see her PMD to be certain that her liver is fine. We will consider using Afamelanotide (Scenesse) when it becomes available in the USA.
I think that I may have seen one or two cases of EPP presented at meetings – I do not recall ever having made the diagnosis clinically. In all honesty, I would not have done so here either. I have to admit, I have a “textbook” image in my mind – a child presenting with immediate pain and burning with sun exposure, who then develops the classical appearance. My patient developed her disease as a child – it just took some time for her to get the right diagnosis.
Interestingly, though, there are milder forms which may not give the classic appearance; indeed, the skin may appear normal. When presenting as an adult, one must consider the possibility of an “acquired” ferrochelatase (FECH) deficiency due to somatic mutations secondary to a myelodysplastic syndrome.
Alternatively, there are now reports of acquired EPP from novel germline mutations in the FECH gene whose late onset is a product of this mutation. The pathomechanism to explain this delayed penetrance remains to be defined. (Azad J, et al. New mutation identified in two sisters with adult-onset erythropoietic porphyria. Clin Exp Dermatol 2013; 38: 601-5).
We should always be thinking about the possibility (however remote) of porphyria whenever anyone has a photoeruption. I’m not recommending testing everyone, just giving it some thought. On a day that I gave it no thought whatsoever, I’m glad my patient reminded me, and taught me to expand my concept of EPP.