FAM20A and primary failure of tooth eruption: Another interesting finding was detecting Fam20a gene expression in the parathyroid gland, given the failure of posterior tooth eruption in AIGFS and ERS and that primary failure of tooth eruption (PFE, OMIM #125350) can be caused by mutations in PTH1R (OMIM 168468; 3p21.31), the gene encoding a receptor for both parathyroid hormone and parathyroid hormone-related protein [36].