Abstract 39

BILATERAL congenital pseudoarthrosis of the clavicles without mutation of the Cbfa1/Runx2 gene

¹David Thomas, ²Michael J Sandow, ³Andreas Evdokiou, ³David M Findlay

¹Department of Medicine, University of Melbourne at St Vincent's Hospital, Fitzroy, Victoria, ²Department of Orthopaedics and Trauma, Royal Adelaide Hospital and Wakefield Orthopaedic Clinic, and ³Department of Orthopaedics and Trauma, University of Adelaide and Hanson Institute, Adelaide.

Purpose of the study: We have identified a 21 year-old male with bilateral pseudoarthrosis of the clavicles, presumed to be congenital. Since the genetic basis of pseudoarthrosis of the clavicle has not been identified, we investigated the possible involvement of mutation of the Cbfa1/runx2 gene. Cbfa1/runx2 is a transcription factor that plays an essential role in osteogenesis, and mutant forms have been linked to cleidocranial dysplasia (CCD), a congenital condition characterized by skeletal anomalies that include hypoplastic and/or aplastic clavicles.

Methods: A shoulder to neck CT was obtained and 3D reconstruction of images was performed using the ®True Life Anatomy software. DNA was extracted from peripheral blood white cells and the gene was amplified by PCR, using intron- and exon-specific primers, and these gene segments were sequenced.

Summary of results: All 7 exons of the Cbfa1/runx2 gene were examined by direct sequencing of PCR products generated from DNA samples from the proband and his parents. No mutations were identified in any coding region or splice-donor/acceptor sites in the Cbfa1/runx2 gene in any of the samples.

Conclusions: The genetic basis for congenital pseudoarthrosis of the clavicles remains to be determined. It is likely that finding the gene or genes associated with this condition will provide fresh insights into skeletal development and into the unique and interesting clavicular bone, in particular.

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