PHEX and X-linked dominant hypophosphatemic rickets: Caspase-12 deficient bone phenotype has not yet been analyzed but alkaline phosphatase deficiency in mice causes hypophosphatasia and impaired mineralization of bone and cartilage (Fedde et al., 1999), osteocalcin-deficient mice develop higher bone mass phenotype with bone defects (Ducy et al., 1996) and Phex mutation is associated with X-linked dominant hypophosphatemic rickets involving impaired bone mineralization (Francis et al., 1997).