Based on the functions of the reported causative genes (SLC20A2, PDGFRB, PDGFB, XPR1, MYORG, and JAM2), the genetic etiology of PFBC can be classified into two categories: imbalance of inorganic phosphate (Pi) and dysfunction of the neurovascular unit (NVU) in the brain. The gene discussed is XPR1; the disease is bilateral striopallidodentate calcinosis.