Cleidocranial dysostosis

Cleidocranial dysostosis  or dysplasia is a genetically transmitted skeletal dysplasia  affecting mainly membranous bones. It is a relatively rare condition, first described by Marie and Fenton in 1897. The  condition that primarily affects the development of the membranous bones and teeth. Signs and symptoms of cleidocranial dysplasia can vary widely in severity, even within the same family.

The condition affects both sexes equally, and may be transmitted by either father or mother, to sons or daughters. Several cases are reported, however, in which neither a familial nor a hereditary history was discoverable.

Deformities in Cleidocranial Dysostosis

Clavicle

The following varieties of defect of the clavicle may be distinguished

• Ends of the bone are normal, but there is a pseudarthrotic gap filled with connective tissue between.
• Partial defect of one end, usually the acromial end which is replaced by fibrous tissue.
• Whole clavicle is absent.

Sometimes the scapula is absent in addition. In these cases,  the deformity is regarded as an aplasia of the whole shoulder girdle rather than a dysostosis.

Muscles

• The clavicular portion of the trapezius may be absent
• Maldevelopment of the pectoralis major
• The clavicular portion of the deltoid may deficient
• There may be a wide variation in the form of the sternomastoid.

Skull

Many there malformations have been reported in association with defective clavicles. Some of these are

• Brachycephaly and dolichocephaly
• Malformations of the various sutures, fontanelles and bones of the skull
• Malformation of facial bones
• Disturbances of dentition

Other Associated Conditions

• Variations in the small bones of the hands and feet
• Deformities of the thorax, spine and pelvis
• Prolapsed of the virginal uterus
• Inguinal hernia
• Spina bifida.

Cause and Pathophysiology

Mutation in CBFA1 gene appears to be  the causative factor. It could be genetically transmitted or result of sporadic mutation. This mutation leads to incomplete intramembranous ossification of midline skeletal structures inclusive of the clavicle as well as defective development of the pubic bones, vertebral column, and long bones.

Clinical Presentation of Cleidocranial Dysostosis

The patient is usually brought to the surgeon on account of some accidentally discovered trouble with the shoulder.

Examination usually shows an apparently un-united fracture, or complete absence, of the clavicle, and the patient can usually approximate the tips of his shoulder to each other below the chin.

The defect is bilateral 80% of the cases. There is a spectrum of clinical features which patient might have. All patients may not have all the features.

Due to underdeveloped bones and joints, people are shorter and their frames are smaller.

Following are the other clinical features that might be present

• Large head, with large fontanelles with delayed closure. A soft area in the top of the head where the fontanelle failed to close, may be palpated. Bulging forehead may be present
• Broad mandible mainly due to hypoplasia of maxilla and other bones
• Supernumerary teeth, failure of eruption of permanent teeth
• High arched palate
• Excessively mobile shoulders
• Genu valgum
• Short fingers with hypoplasia of terminal phlanges
• Hypertelorism
• Widened symphysis due to delayed ossification of bones
• Varus deformity at hip [coxa vara]
• Scoliosis, spina bifida and syringomyelia have also been described
• Basilar invagination
• Abnormal ear structures with hearing loss,
• Supernumerary ribs
• Hemivertebrae with spondylosis
• Small and high scapulae
• Iliac bone hypoplasia
• Short/absent fibular bones, radial bones

Imaging

Xrays of different regions show different findings

Skull

• Wormian bones – These are extra bone pieces in the sutures of skull
• Wide sagittal sutures and/or fontanelles
• Brachycephaly or short skull – This occurs due to premature fusion of the coronal suture
• Basilar invagination or atlantoaxial impaction – It refers to invagination or infolding of the base of the skull that occurs when the top of the C2 vertebra migrates upward.
• Persistent metopic suture
• Supernumerary or abnormal teeth
• Abnormal ear structures

Chest

• Hypoplasia/aplasia of lateral clavicle (absent clavicles): may have two separate hypoplastic segments
• Supernumerary ribs
• Hemivertebrae with spondylosis
• Small and high scapulae

Pelvis

• Hypoplasia of iliac bones
• Absent/delayed ossification of the pubic bone (Appears as widening of the symphysis pubis)

Extremities

• Short/absent fibula
• Short/absent radius
• Coxa vara
• Hypoplastic terminal phalanges

Treatment of Cleidocranial Dysostosis

If pain is present from the pressure of one or other of the ends or there is brachial plexus irritation causing pain and numbness, then removal of the part is indicated. As a rule there is little or no disability or discomfort and the abnormal mobility is not usually a hindrance.

Some surgeons prefer surgical correction  to prevent any worsening of the deformity.

Supranumery teeth need to be removed as they will crowd the teeth in already underdeveloped jaw.

Craniofacial surgery may be necessary to correct skull defects.