PDGFB and bilateral striopallidodentate calcinosis: The simultaneous discovery that mutations in PDGFB and PDGFRB can also cause primary familial brain calcification (PFBC) demonstrates new functions of PDGF-Rβ signaling that could not have been predicted based on existing knowledge about PDGF-B/ PDGF-Rβ functions, demonstrating that there is still much to be learnt about PDGF biology [14,15].