Expressions of apolipoprotein E (APOE), F (APOF) and L5 (APOL5) were decreased in PXE samples (patient/control ratio: 0.07; patient/control ratio: 0.5; patient/control ratio: 0.2, respectively), whereas a reduction in APOE expression was also confirmed by siRNA treatments (siABCC6/siNK ratio: 0.5). This evidence concerns the gene APOE and Pseudoxanthoma elasticum.