RUNX1 and cleidocranial dysplasia 1: The occurrence of CCD in patients with a mutation in the RUNX1 gene appears to be particularly relevant for two reasons: (a) Blood malignancies demonstrating mutations at the equivalent residues RUNX1-2 suggest a common leukemogenic pathway [17], (b) RUNX2 is an important gene in osteoblastic activity and in teeth development process [18].