dysostoses

Dysostoses are congenital abnormalities of the skeletal system that arise from defective development of bone and cartilage during embryogenesis. They result from problems in the formation of ossification centers or in the segmentation and articulation between bones. Dysostoses may be isolated or part of a syndrome, and they may involve the skull and facial bones, clavicles, vertebrae, ribs, and limbs. They are distinguished from skeletal dysplasias, which primarily involve abnormalities of bone growth and modeling.

Pathogenesis includes failure of formation (agenesis or hypoplasia) and failure of segmentation (synostosis) between adjacent bones. The resulting malformations may be unilateral or bilateral, fusiform or missing bones, and can lead to functional impairment or cosmetic concern. Patterns vary widely and may be present at birth or become evident with growth.

Well-known examples include cleidocranial dysostosis, with underdeveloped or absent clavicles and delayed cranial suture closure; Jeune or asphyxiating thoracic dysostosis, characterized by a narrow, underdeveloped thoracic cage; and the widespread dysostosis multiplex seen in several mucopolysaccharidoses.

Diagnosis relies on clinical examination and imaging, including radiographs and cross-sectional studies, with genetic testing used for syndromic forms. Management is multidisciplinary, addressing functional and respiratory risks, with orthopedic or craniofacial procedures as needed and ongoing surveillance.

Prognosis depends on severity and associated anomalies; mild cases may have good function, while severe thoracic dysostoses can be life-threatening.