TY - CHAP M1 - Book, Section TI - Hypophosphatasia A1 - Bianchi, Diana W. A1 - Crombleholme, Timothy M. A1 - D'Alton, Mary E. A1 - Malone, Fergal D. PY - 2015 T2 - Fetology: Diagnosis and Management of the Fetal Patient, 2e AB - Key PointsRare hereditary metabolic bone disorder characterized by deficient activity of the tissue-nonspecific isoenzyme of alkaline phosphatase (TNSALP).Incidence is 1 in 100,000 births in most ethnic groups but 1 in 2500 in Canadian Mennonites.Two forms present perinatally: severe (lethal) and benign, which resolves spontaneously.In the severe form sonographic findings include increased nuchal translucency measurement, undermineralized skull, shortened, bent, fixed limbs with decreased echogenicity, and lack of ossification of vertebral bodies, neural arches, and hands. The benign perinatal form presents with symmetric bowing of long bones.Differential diagnosis includes anencephaly, osteogenesis imperfecta types II and III, thanatophoric dysplasia, campomelic dysplasia, achondrogenesis, and cleidocranial dysplasia.Amniocentesis should be offered to rule out anencephaly, confirm fetal karyotype, assay alkaline phosphatase activity, and check for DNA mutation(s).Causative gene is TNSALP.Severe form is recessively inherited with two mutations. Milder form is dominantly inherited with one mutation.Genetic consultation and counseling are indicated. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/10/03 UR - obgyn.mhmedical.com/content.aspx?aid=1106400302 ER -