Erythropoietic protoporphyria (EPP) is a rare genetic disorder associated with mutations in the FECH gene. EPP is characterized by photosensitivity, resulting in severe skin reactions upon exposure to sunlight. While this condition affects individuals worldwide, notable demographic differences have been observed between northern European countries and those in southern regions.

In northern countries, the prevalence and incidence of EPP tend to be higher (Norway 27.7/10⁶ and 0.36/10⁶; Switzerland 27/10⁶ and 0.35/10⁶; United Kingdom 25.4/10⁶ and 0.33 x 10⁶ respectively) compared to southern countries (Spain 2.3/10⁶ and 0.03/10⁶; Italy 5.4/10⁶ and 0.07/10⁶). The factors that could explain this difference may be genetic: the frequency of mutations in the FECH gene in the north could be higher than in the south. Environmental conditions may also play a role: clinical expression could be reduced due to a ‘hardening’ phenomenon secondary to sun exposure, which makes it easier for patients to live with the disease without the need to seek attention from a healthcare provider.

We present a series of 37 patients diagnosed with EPP in the main two tertiary reference centers for porphyrias in Spain. Mean average age of symptom onset was 15 years with 51% making their debut in the first decade of life while 16% made their debut over 40 years. Mean age at diagnosis was 16 years and 4 months.

This study aims to present and compare sociodemographic and genetic data between a series of Spanish patients with data from Nordic European countries. Understanding these demographic variations could be crucial for comprehension, effective management, and support for individuals living with EPP.