Dysostosis

Dysostosis is a term used in medicine to describe congenital malformations of bones that arise from abnormal development of skeletal tissue during embryogenesis or from failure of segmentation of cartilaginous precursors. It is contrasted with dysplasia, which refers to overall abnormal bone growth and remodeling. Dysostoses may be isolated or occur as part of broader syndromes and can involve the skull, clavicles, digits, ribs, spine, or pelvis. Manifestations range from absent or hypoplastic bones to abnormal fusion or segmentation defects and can be detected at birth or in early childhood.

Common examples include cleidocranial dysostosis (cleidocranial dysplasia), characterized by partial or absent clavicles, delayed closure of cranial sutures, brachycephaly, midface hypoplasia, and dental anomalies; and thrombocytopenia-absent radius (TAR) syndrome, which features radial ray defects with thrombocytopenia. Other dysostoses may affect the thoracic cage, vertebrae, or digits and may occur as single anomalies or as part of complex multisystem disorders.

Diagnosis relies on clinical assessment and radiographic imaging that shows bone formation and segmentation abnormalities. Genetic testing can confirm syndromic forms and guide counseling.

Management is typically multidisciplinary and tailored to the individual. Treatments may include orthopedic procedures to improve function, craniofacial or dental interventions, physical therapy, and supportive care for associated health issues. Prognosis varies with the extent and severity of the anomalies and the presence of comorbid conditions.