Prenatal screening, dx, tx Flashcards
cystic fibrosis - what kind of inheritance?
AR
median survival for CF patients
30 years
what are the 2 most common mutations in CF?
deltaF508 and G542X
what is risk of fetus being + for an AR disorder if both mother and father are carriers? What is next step if both parents are found to be carriers?
25%. Amniocentesis or CVS to dx fetus.
rate of CF carriers among caucasians
1 in 28
pattern of inheritance for sickle cell
AR
who should be screened for sickle cell?
all pg AfAms
pattern of inheritance for tay-sachs
AR
signs & sx’s of tay-sachs:
occur 3-10mos after birth. loss of alertness hyperacusis progressive neuro'c degeneration, dvp'l delay myoclonic & akinetic seizures cherry-red spots on retina (macular fovea centralis is red, macula is pale) paralysis, blindness, dementia death by age 4
Tay-Sachs is a def’y of what?
enz def’y (hexA) which is responsible for ganglioside degradation.
Results in ganglioside accumulation in brain gray matter neurons => neuronal death.
who gets screened for Tay-Sachs
ashkenazi Jews, French canadians
when is beta thalassemia dx’d? More common in who?
several months after birth, when the beta-globin chain starts to replace fetal gamma-globin chains. More common in Mediterranean, Asian, African
what are the different types of alpha thalassemia?
4 diff alleles encode alpha globin gene.
Deletion of 1 alpha-globin gene = silent carrier, asx’c.
deletion of 2 = alpha-thal trait. Normal Hb electrophoresis, mild pht.
deletion of 3 = HbH dis. excess beta chains
accumulate
deletion of all 4 = hydrops fetalis. They only produce HbBart.
how do you screen for thalassemias?
do a CBC in high-risk populations. If microcytic anemia is found, then do Hgb electrophoresis.
cis vs. trans mutations of alpha globin gene: which is more common in who?
cis = 2 alpha globin muts, both on same chrom. More common in Asians. trans = 2 alpha globin muts, on diff chroms. More common in Africans.
why is dtm’n of cis vs. trans mutation important?
if both parents have cis mut, then there’s a 25% chance that fetus will dvp hydrops fetalis. If both have trans, the child will get the trans mut and will be an asx’c carrier.
when to screen for trisomy 21 and how?
use triple or quad screen, b/w 15 and 19 weeks (second trimester)
first trimester screen for down syndrome =
nuchal translucency + b-hCG + PAPP-A (pg’y-ass’d plasma prot A)
Trisomy 18 is screened for how?
triple screen during 2nd tri
findings of trisomy 18 (Edward syndrome)
clenched fists, overlapping digits, rocker bottom feet seen on u/s. VSD, tetralogy of fallot, omphalocele, congenital diaphragmatic hernia, neural tube defects, choroid plexus cysts.
Incompatible w/life beyond age 2.
Trisomy 13 is screened for how?
Not detected by triple screen but on routine screening u/s. CP is similar to trisomy 18. Most do not live beyond 1 year. Holoprosencephaly, cleft lip, cleft palate, cystic hygroma, single nostril or absent nose, omphalocele, hypoplastic left heart, club foot, club hand, polydactyly, overlapping fingers.
what are the most common sex chromosome abnormalities?
Turner (45X), Klinefelter (47XXY)
CP of turner syndrome
pht’lly female, primary amenorrhea, webbed neck, low-set ears, wide carrying angle, shield chest, short 4th metacarpal, renal anomalies, lymphedema, coarctation of aorta, cystic hygroma seen on prenatal u/s.
screening for Turner syndrome?
none. Dx’d w/CVS.
screening for Klinefelter syndrome?
none. Dx’d w/CVS.
CP of Klinefelter:
small, firm testes at puberty, infertility, gynecomastia, mental retardation, elevated gonadotropin levels.
what 2 chromosomal abnormalities are screened for on the triple or quad screens?
Trisomy 21 and 18.
what is a morula & when does it dvp?
16-cell embryo, day 4
