Genotype phenotype correlation in achondroplasia and hypochondroplasia

Recent studies of the fibroblast growth factor receptor 3 (FGFR3) gene have established that achondroplasia and hypochondroplasia are allelic disorder s of different mutations. To determine whether the genotype could be distinguished on the basis of th e phenotype, we analysed height, arm span, and skeletal radiographs from 23 patients with achondroplasia and the G380R mutation of FGFR3 and eight wit h hypochondroplasia and the N540K mutation. Both conditions share the class ical pathological features of micromelic short stature, reduced or unchange d interpedicular distances int the lumbar spine, disproportionately long fi bulae, and squared and shortened pelvic ilia, These were! significantly mor e severe in the G380R patients than in the N540K patients. Our findings have shown a firm statistical correlation between the genotype and the phenotype, although there were a few exceptional eases ill which t here was phenotypic overlap between the two conditions.