Initial studies using Akp2 knockout (TNAP-/-) mice, a well-establish model of infantile HPP, suggested that seizures were a consequence of diminished levels of GABA in the brain, caused in turn by a defective metabolism of vitamin B6 (Waymire et al., 1995; Narisawa et al., 1997, 2001). Here, ALPL is linked to hypophosphatasia.