Prenatal sonographic diagnosis of hypochondroplasia in a high-risk fetus

Hypochondroplasia (HCH) is caused by mutations in the fibroblast growth fac tor receptor type 3 (FGFR 3), Prenatal diagnosis of HCH based exclusively o n the sonographic measurements of the fetal skeleton is difficult and has n ot been reported. We describe a newborn infant with HCB who was born to a m other with achondroplasia (ACH) and a father with HCH, Serial sonographic m easurements were recorded from 16 weeks of gestation. All measurements rema ined normal up to 22 weeks of gestation. At 25 weeks of gestation, the long bones began to appear shorter than expected for gestational age, while the head measurements (biparietal diameter and head circumference) remained no rmal. The measurements were sufficiently different to distinguish from find ings in normal and achondroplastic fetuses. Our findings suggest that it is possible to distinguish the normal fetus from a fetus affected with HCH an d to distinguish HCH and ACH from each other based on the sonographic measu rements alone. To our knowledge, this is the first report of longitudinal s onographic measurements of HCH in the second and third trimesters. Am. J. M ed. Genet. 87:226-229, 1999. (C) 1999 Wiley-Liss, Inc.