The diagnostic dilemmas of skeletal dysplasia: classification, incidence and mode of inheritance of different type (a clinical and radiological overview)
Skeletal dysplasia are a primary result of mutation genes that are expressed in chondro-osseous tissue. However, there are also some other forms of secondary dysplasia caused by abnormalities of extra-osseous factors with effects on the skeletal system like metabolic errors in hypophosphatemic rickets. International nosology and classification of genetic disorders of bone (published 2009) includes 37 groups; from 250 well defined disorders about 70 are often lethal in the perinatal period. Primarily the classification of skeletal dysplasia is based on radiological features of skeletal changes. However, the progress in molecular genetics especially in the last decade permit owing to distinctions at the DNA level refinements in classification resulting in an increasing number and subtypes of dysplasias. The similarity of morphological findings with or without the same inheritance as well as their rare incidence are all reasons for diagnostic dilemma in this field. The first step in the diagnosis of skeletal dysplasia is to observe a disproportionate skeletal development, unusual habitués with or without mental retardation as well as other clinical signs. The second step is more difficult and includes genetic counseling and interpretation of radiologic skeletal changes in affected patients and their families. The rare incidence of skeletal dysplasia on one hand and its morphologic diversities on the other hand require some experience and therefore, centralization of knowhow in this field is recommendable. In this manner medical geneticists and radiologists gain the ability and expertise in this field. The aim of this presentation is to give an overview of skeletal dysplasia; a large number of different types will be shown. Special attention should be paid to their inheritance, molecular pathology and incidence as well as the radiological findings.