SLC20A2 and bilateral striopallidodentate calcinosis: PiT2 proteins can oligomerize, and the variant proteins might exert their dominant negative effect, either by reducing the amount of Pi-transport-capable PiT2 oligomers in the cell membrane and/or, as observed by Kimura et al. (Kimura et al. 2015) in a PFBC patient, by reducing the amount of WT and variant PiT2 proteins in the cells.