The presence of germ line mosaicism in cleidocranial dysplasia

Cleidocranial dysplasia (CCD) is typically an autosomal dominant condition. The possibility of alternative causes, such as an autosomal recessive form or germ line mosaicism, have been suggested in some families with CCD, but not proven. We present a family consisting of a mother having three sons affected with CCD. One of the affected boys is a half brother to the other two affected children. The diagnosis of CCD was confirmed by DNA analysis of the RUNX2 gene in all three of the boys in blood; however, initial DNA testing in the mother's blood did not detect the presence of a RUNX2 mutation in the mother. Further testing through heteroduplex analysis applying high-resolution melting analysis followed by subcloning detected low-level mosaicism in DNA isolated from maternal blood and buccal swab, confirming low-level mosaicism in somatic cells. We present the first case of confirmed germ line mosaicism in CCD.