Definition
An autosomal dominant skeletal dysplasia of membranous and endochondral bone, with clavicular hypoplasia, delayed skull ossification and dental anomalies.
Aetiology
- Heterozygous loss of function mutation of RUNX2 (CBFA1) on chromosome 6p21
- RUNX2 controls osteoblast differentiation
- New mutations occur without a family history
Epidemiology
- About 1 in 1,000,000 births
- Equal sex distribution, with variable expression within families
Clinical Features
- Hypoplastic or absent clavicles, allowing the shoulders to meet in front of the chest
- Open fontanelles, wide sutures, frontal bossing and Wormian bones
- Supernumerary and retained teeth with delayed eruption
- Mild short stature
- Coxa vara and genu valgum
- Short middle phalanges and cone shaped epiphyses in the hand
- Scoliosis and spondylolysis
Investigations
- Chest radiograph shows lateral clavicle deficiency, often bilateral
- Pelvis shows delayed pubic ossification with a wide symphysis
- Skull radiograph shows open sutures and Wormian bones
- RUNX2 genetic testing confirms the diagnosis
Differential Diagnosis
- Congenital pseudarthrosis of the clavicle, a right sided midshaft defect with a normal skull
- Clavicle birth fracture, which forms callus
- Pycnodysostosis
Management
- Observation. Clavicular deficiency rarely limits shoulder function
- Proximal femoral osteotomy. Valgus osteotomy for progressive coxa vara
- Dental care. Staged extraction and orthodontic surgery
- Scoliosis care. Bracing or fusion by standard indications
Prognosis
- Normal intelligence and life expectancy
- Conductive hearing loss and recurrent sinus and ear infections in some
References
- Mundlos S. Cleidocranial dysplasia. Clinical and molecular genetics. J Med Genet. 1999, 36(3), 177-82. PubMed
- Mundlos S, Otto F, Mundlos C, Mulliken JB, Aylsworth AS, Albright S, Lindhout D, Cole WG, Henn W, Knoll JH, Owen MJ, Mertelsmann R, Zabel BU, Olsen BR. Mutations involving the transcription factor CBFA1 cause cleidocranial dysplasia. Cell. 1997, 89(5), 773-9. PubMed
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 19 October 2026.