RT Book, Section A1 Bianchi, Diana W. A1 Crombleholme, Timothy M. A1 D'Alton, Mary E. A1 Malone, Fergal D. SR Print(0) ID 1106400262 T1 Achondrogenesis T2 Fetology: Diagnosis and Management of the Fetal Patient, 2e YR 2015 FD 2015 PB McGraw-Hill Education PP New York, NY SN 978-0-07-144201-5 LK obgyn.mhmedical.com/content.aspx?aid=1106400262 RD 2024/03/28 AB Key PointsSecond most common lethal short-limb dysplasia.Incidence is 1/40,000 to 1/50,000 livebirths.Characterized by severe micromelia, lack of vertebral ossification, and a large head with relatively normal ossification of the calvarium; also associated with polyhydramnios, cystic hygroma, and hydrops fetalis.Type I (20% of cases) is more severe and is inherited as an autosomal recessive. Type IB is caused by a mutation in the diastrophic dysplasia sulfate transporter (DTDST) gene.Type II (80% of cases) is caused by mutations in the COL2A1 gene, which results in significantly decreased type II collagen. Type II is usually a de novo dominant mutation, with rare reports of recurrence due to germline mosaicism.Increased incidence of prematurity and stillbirth. Condition is lethal in perinatal period.