[Prenatal diagnosis of osteogenesis imperfecta. Report of a case classified as the classical Vrolik lethal type].

Report on prenatal sonographic diagnosis of osteogenesis imperfecta of the classical type "letalis Vrolik" in the case of a fetus in the 20th/21st week of pregnancy. The prenatal diagnosis of this kind of osteogenesis imperfecta is based on the soft membranous cranium (Caput membranacium), the microthorax caused by the bell-shaped configuration of the ribs and the diaphysis of the long bones which are too short for the age of pregnancy. These symptoms are first of all the consequence of a disturbed bone formation and mineralisation; its basis is a connatal deficit of collagen synthesis. The sonographic differential diagnosis to the type "Ekman Lobstein" of osteogenesis imperfecta and thanatophoric dwarfism are discussed.