Auxological and Radiological Manifestations of Patients with Hypochondroplasia Negative for N540K Mutation in Fibroblast Growth Factor Receptor 3 Gene

To clarify the auxological and radiological features of hypochondroplasia patients negative for the N540K mutation in FGFR3 gene, eight patients who were radiologically diagnosed as having hypochondroplasia were enrolled in this study (6 males and 2 females)；their median age was 10.9 years (range：5.75-21.75). They were studied for the relationship between auxological and radiological features, and genetic findings. Six patients negative for the N540K mutation had a less severe phenotype, presenting as short stature with less obvious disproportion, with or without relative macrocephaly, and with or without lumbar interpedicular narrowing. These results suggest that hypochondroplasia patients negative for the N540K mutation are heterogeneous in etiology and overlap with constitutional short stature.