The phenotypic overlap observed in Fam20a and Fam20c knockout mice and patients with mutations in FAM20A and FAM20C, including conditions such as amelogenesis imperfecta, gingival fibromatosis, ectopic calcification, and periodontal disease, indicates the close correlation between FAM20A and FAM20C in structural, functional, and developmental aspects (24). The gene discussed is FAM20A; the disease is periodontal disorder.