SPP1 and retinitis pigmentosa 1: In recent decades, RP were found to contain CaP crystalline deposits and to be located in the tubular basement membranes and renal interstitium, appearing as spheres with alternating light and dark rings in which OPN was detected (Evan et al., 2005), and similarities between the context of RP formation and ectopic calcification were identified by light and electron microscopy techniques (Khan et al., 2012).