Practical Approach to Radiologic Diagnosis of Bone Dysplasias: Bone Dysplasia Family

Abstract

“Bone dysplasia family”refers to a group of disorders which share qualitatively similar skeletal alterations and a conceivably common pathogenesis. This concept was first described by Spranger, and has provided a practical guide for the differential diagnosis of bone dysplasias. This idea has since become a pilotage for molecular investigation on this field; for instance, the discovery of heterozygous mutations of the FGFR3 gene in achondroplasia led to the elucidation of other heterozygous mutations of the FGFR3 gene in thanatophoric dysplasia and hypochondroplasia, which had been classed as allelic disorders in the“achondroplasia family”solely based on clinical and radiologic grounds. Understanding the bone dysplasia family concept can facilitate further nosologic and molecular investigations in this molecular era, which will ultimately provide information beneficial to the management of affected individuals. Common“bone dysplasia families”are outlined here, particularly from the radiological standpoint. The importance of phenotype-genotype correlation is discussed by exemplifying the radiologic findings in achondroplastic individuals with uncommon mutations of the FGFR3 gene and radiologic variabilities in a severe form of type II collagenopathy.