Trisomies, Triploidy, and monosomy X
Terms in this set (20)
trisomy 21 is also known commonly as what?
which trisomy? incidence is 1 in 800 births. one of the most common chromosomal disorders. associated with advanced maternal age, abnormal quad screen. 95% due to maternal non-disjunction. 3% due to translocation, 2% due to mosaicism.
trisomy. physical features: brachycephaly (basketball head), epicantahal folds (slanted eyes), flattened nasal bridge, thickened nuchal fold, small ears, protruding tongue. associated anomalies: heart defects, GI atresias, omphalocele, short extremities, sandal foot, hypoplasia of middle 5th phalanx, clinodactaly (curved inward pinky), simian crease (single palm crease)
trisomy. prognosis: mental retardation always present, survival depends on associated anomalies, more anomalies present=worse prognosis, have eye, lung problems and premature aging. mean life span is 49 years. sonographic: increase nuchal translucency, thick nuchal fold, short femur, heart defects, abnormal pinky, duodenal atresia, IUGR, borderline dilation of renal pelvis, ehcogenic bowel, mild ventriculomegaly, absent nasal bone.
what is trisomy 18 also known as?
trisomy. incidence 1 in 3000 conceptions. 1 in 5-8000 births. 2nd most common trisomy carried to term. live birth results in female:male ratio of 3:1. associated with abnormal Quad screen and advanced maternal age. etiology: nondisjunction-occurind during meiosis, translocation-can be inherited, mosaicism.
trisomy. physical findings: cardiac defects-present in vast majority of fetuses with this condition, cranial anomalies (dolichocephaly, microcephaly, hydrocephalus, agencies of CC, cerebellar hypoplasia, etc.) facial abnormalities (low-set ears, micrognathia, cleft lip/palate) extremity abnormalities (clenched hands, club feet, rocker-bottom feet, radial aplasia)
trisomy. associated anomalies: omphalocele, diaphragmatic hernia, neural tube defect (spina bifida, anencephaly), cystic hygroma, renal anomalies. prognosis: many sponatenously abort by second trimester, 90-95% die in 1 year of birth. median life span=5-15 days. profound mental retardation present. sonographic: dolicocephaly, microcephaly, hydrocephaly, micrognathia, cleft lip/palate, clenched hands, club feet, rocker bottom feet, polyhydramnios, IUGR, single umbilical artery, non-immune hydrous
what is trisomy 13 also known as?
trisomy. incidence is 1 in 10,000 live births. associated with advanced maternal age, elevated inhinin A on quad screen, low hCG and PAPP-A. etiology: nondisjunction, translocation, mosaicism. physical findings: cranial defects (holoprosencephaly-common, agencies of corpus callosum, microcephaly, hypotelorism)
trisomy. facial defects (proboscis, cyclopia, nose with single nostril, cleft lip/palate, micropthalmis, micrognathia) all associated with holoprosencephaly. heart defects (present in 90% of cases. VSD, ASD, hypoplastic left heart)
trisomy. associated anomalies: omphalocele, renal anomalies, meningomyelocele, limb anomalies (polydactyly, talipes, rocker-bottom feet, overlapping fingers), cystic hygroma, echogenic chordae tendinae. prognosis: 82% die within 1 month of birth, considered lethal anomaly, medial life span=2.5 days, survivors profoundly retarded with many problems
trisomy. sonographic findings: sonographic characteristics seem in 90% of babies with this trisomy. holoporsencephaly, microcephaly, agenesis of corpus callosum, hypotelorism, cyclopia, micropthalmia, proboscis, cleft lip/palate, micrognathia, VSD, ASD, hypoplastic left heart, omphalocele, meningomyelocele, cystic kidneys, polydactyly, talipes rocker-bottom feet, overlapping fingers, IUGR
have three complete sets of chromosomes. mechanism: diandry, digyny. incidence: occurs in about 2% of conceptions, but most abort in the first trimester. 1 in 2500 live births.
mechanism for triploidy. results of ovum fertilized by two sperm. found in partial molar pregnancies as well. more than 50% will miscarry
mechanism for triploidy. single sperm fertilizes ovum containing two complete sets of chromosomes. most that survive to birth are this form
physical findings. heart defects, renal anomalies, omphalocele, meningomyelocele, cranial defects (holoprosencephaly, agenesis of corpus callosum, hydrocephalus, dandy-walker), facial defects (low-set ears, hypertelorism, cleft lip/palate, micrognathia), cryptorchidism, ambiguous genitalia, syndactyly, talipes
prognosis- the few who survive the gestational period die shortly after birth. considered lethal condition (rarely survive two months, all die within 1 year), mosaic form of triploidy may be compatible with survival, but they will be mentally retarded and have health problems. sonographic: holoprosencephaly, agenesis of corpus callosum, dandy walker, hydrocephalus. hypertelorism, cleft lip/palate, micrognathia, syndactyly, talipes, ambiguous genitalia, severe IUGR, hydatidiform degeneration of placenta, oligohydramnios
turner syndrome (45X)
incidence: 1 in 8000 births, 98% result in miscarriage, not associated with maternal age, occurs more often in japanese, absence of sex chromosome from sperm, always FEMALE. physical findings: cystic hygroma, coarctation of aorta, other heart defects, lymphedema, hydrops, horseshoe kidney, renal agenesis, hypoplastic kidney, hydronephrosis, short femurs
prognosis: most abort spontaneously, fetus with large cystic hygroma/hydrops has poor prognosis, survival after birth depends on severity of anomalies, survivors will be female, have immature sexual development, amenorrhea, short stature, webbed neck, abnormal, elbow angle, and shield chest with widely with widely spaced nipples. usually normal intelligence. sonographic: cystic hygroma, coarctation of aorta, renal anomalies, short femurs, oligohydramnios