SLC20A2 and microphthalmia: Slc20a2-HO mice, with 19% relative Slc20a2 gene expression, exhibited some unique overall appearances, such as developmental delay, skeleton malformation, cataract, or microphthalmia (Wallingford et al., 2016, 2017; Jensen et al., 2018; Beck-Cormier et al., 2019), which were not observed in patients with heterozygous SLC20A2, even barely in those harboring compound heterozygous or homozygous SLC20A2 mutations (Wang et al., 2012; de Oliveira et al., 2013; Borges-Medeiros et al., 2019; Chen et al., 2019).