Molecular defects causing skeletal dysplasias.

Almost 400 different forms of skeletal dysplasias have been described, each with characteristic clinical and radiographic features. The underlying genetic and molecular pathology is known in several forms. Correct diagnosis is important for genetic counseling, treatment decisions, follow-up and for predicting long-term outcome. With advances in molecular genetics it has become evident that variable phenotypes can be caused by mutations in one gene, depending on the mutation type and location within the gene. On the other hand, mutations in different genes can result in similar phenotypes. Careful clinical assessment with thorough radiographic evaluation are of key importance.