title: Defects of blastogenesis: counseling dilemmas in two families.
abstract: Three patients are described with defects of blastogenesis and predominantly midline defects. Two were sibs of whom the firstborn were female cephalothoracopagus-conjoined twins with multiple predominantly midline defects initially thought to be a sporadic occurrence. A subsequent brother presented with severe hydrocephalus, rhombencephalosynapsis, conotruncal defect, ambiguous genitalia, and unilateral pre-axial polydactyly; an autosomal recessive defect is postulated in this case. Patient 3 had hydrocephalus, small cerebellum, cleft lip and palate, and a large sacrococcygeal teratoma, the better differentiated part of which included ovarian tissue with primordial follicles. The latter may occur in incomplete twinning as a defect of blastogenesis. The mother had had a previous termination of a fetus with hydrocephalus from a different relationship. Counseling was difficult since no examinations were done on the previous fetus and no further investigations of this family could be obtained, but a genetic origin is suspected. Most defects of blastogenesis are sporadic; however, some cases have a genetic cause and ultrasound examinations should be offered in subsequent pregnancies.
authors.affiliation: Division of Human Genetics, University of Stellenbosch and Tygerberg Hospital, Tygerberg, South Africa.
authors.forename: G
authors.initials: G
authors.lastname: de Jong
authors.forename: P A
authors.initials: PA
authors.lastname: Kirby
mesh_terms: D000015:Abnormalities, Multiple / Q000000981:diagnostic imaging; D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D005260:Female; D005817:Genetic Counseling; D006801:Humans; D006849:Hydrocephalus / Q000000981:diagnostic imaging; D008297:Male; D011247:Pregnancy; D014428:Twins, Conjoined; D016216:Ultrasonography, Prenatal