By searching for biomarkers in biological fluids of PXE patients, we and others observed that unaffected first-degree relatives mostly display results, e.g., for serum fetuin-A, desmosine, that were different from normal and intermediate between that of the PXE patients and the controls (Annovazzi et al., 2004; Hendig et al., 2006). This evidence concerns the gene AHSG and Pseudoxanthoma elasticum.