Heterozygous loss-of-function mutations in RUNX2 lead to cleidocranial dysplasia (CCD, MIM #119600), while gain-of-function mutations result in metaphyseal dysplasia with maxillary hypoplasia with or without brachydactyly (MDMHB, MIM #156510) and nonsyndromic midline craniosynostosis1–3. Here, RUNX2 is linked to cleidocranial dysplasia 1.