Cleidocranial Dysplasia with Normal Clavicles: A Report of a Novel Genotype and a Review of Seven Previous Cases.

We report an unusual combination of features comprising delayed tooth eruption and closure of the anterior fontanel as the sole presenting features in a child with cleidocranial dysplasia (CCD). Radiological survey revealed the presence of wormian bones in the skull, pseudoepiphysis at the base of the bilateral second metacarpal, and midline ossification defects at pubic symphysis in the presence of essentially normal clavicles. DNA sequencing of the RUNX2 gene detected a novel nonsense mutation in exon1 (c.166C>T; p.Q56X) in its glutamine-alanine (Q/A) repeat domain. The genotypes of all published cases of CCD with normal clavicles were reviewed. Additional dental and otolaryngological features were enlisted. Three cases with a milder dental phenotype and normal clavicles were associated with a mutation in the Q/A domain. Collectively, we found a novel CCD-causing nonsense mutation p.Q56X in the Q/A domain of the RUNX2 gene.