FECH and nutritional disorder: Interestingly, the exact cause for the iron deficiency in EPP1 patients remains unclear: On the one hand, hepcidin, a hepatic peptide hormone that regulates iron homeostasis and prevents iron uptake und release from the body iron stores during inflammation is not upregulated and therefore does not prevent nutritional iron absorption in EPP1 (Bossi et al., 2015; Barman-Aksozen et al., 2017; Graziadei et al., 2022).