PIGO and hyperphosphatasia-intellectual disability syndrome: Besides this there have been only a few sporadic IGD cases reported in China, including one MCAHS1 case caused by PIGN variants, and two Mabry syndrome (i.e., HPMRS1, MIM 239300 and HPMRS2) cases caused by PIGV (MIM 610274) and PIGO variants, respectively (Xu et al., 2017; Xue, Li, Zhang, & Yang, 2016).