Peds- Genetics Flashcards
Quadruple screen
alpha-fetoprotein (AFP)- high in neural tube defects, skin disruptions (omphalocele); low in trisomies 21, 18, 13 (50% sensitive) unconjugated estriol (ue3/ E3) inhibin A human chorionic gonadotropin (hCG)
When the quadruple screens are used together what do they detect?
80% sensitive for 3 trisomies:
trisomy 21- low E3 & AFP, high hCG
trisomy 18- all low
trisomy 13
Genetic Screening Tools
fetal ULS
amniocentesis
chorionic villus sampling
Genetic Testing
karyotype
fluorescent in-situ hybridization (FISH)
polymerase chaine reaction
direct enzyme testing (fibroblasts)
Karyotype
chromosomes of cultured cells viewed directly
allows counting & visualization of gross defects
FISH
fluorescent probe seeks out known defects
PCR
allows direct analysis of a gene
MC sex chromosome abnormality?
Kleinfelter’s (~1:500)
MC autosomal chromosome abnormality?
Down Syndrome (~1:600)
Aneuploidies
monosomies
triploidies
elimination or duplication of sex chrom
Triple repeat expansions
threaten chromosomal stability
Specific Aneuploidies
Down Syndrome
Trisomies 18 & 13
Keinfelter syndrome
Turner syndrome
Down Syndrome head & neck characteristics
small, brachycephalic head upslanting palpegral fissures epicanthal folds flat nasal bridge small, folded/dysplastic ears midface hypoplasia protruding tongue short neck excessive skin at nape of neck
Down syndrome extremities characteristics
short broad hands hypoplastic middle phalanx of 5th finger incurved 5th finger transvers palmar crease space between 1st & 2nd toes hyperlexibility of joints hypotonia
Down Syndrome cardiac characteristics
endocardial cushion defect
VSD
ASD
Down syndrome GI characteristics
esophageal or duodenal atresia
GERD
Down Syndrome Endocrine characteristics
thyroid dysfunction
short stature
DM
Down Syndrome Ortho characteristics
atlanto-axial instability
Down Syndrome Hematologic Characteristics
leukemoid rxn
increased incidence of leukemia
DS eye characteristics
refractive errors
strabismus
nystagmus
cataracts
DS immune characteristics
poor chemotaxis
DS other characteristics
hearing deficits
obesity
obstructive sleep apnea
Medical mgnt for DS
cardiac eval hematologic eval ophthalmologic referral thyroid function screening obesity screening nutritional counseling dental eval for peridontal dz annual hearing screening
Turner’s Syndrome
monosome X (XO, or 45,X) caused by loss of part/all of an X chromosome resulting in monosomy XO
Characteristics of Turner’s syndrome
females 1:2000 (causes ~15% of SAB) webbed neck edema of hands & feet, often at birth short stature shield chest triangular facies
Cardiac abnormalites in Turner’s syndrome
coarctation of aorta
mitral & aortic valve abnormalities
GYN problems with Turner’s syndrome
amenorrhea & infertility (streak ovaries)
ovarian failure
absence of secondary sex characteristics
Frequent types of therapy used in Turner’s Syndrome
growth hormones
thyroid hormones
estrogen replacement
Turner’s syndrome general
about 1/3 have renal anomalies
obesity, DM, HTN
life expectancy reduced ~10 yrs
Kleinfelter’s syndrome
abnormal # of sex chromosomes
47 XXY karyotype
defect in meiosis of paternal/maternal origin
may have further excess X chromosomes
Kleinfelter’s syndrome characteristics
hypogonadism small penis, small testes tall, slim stature developmental delay mental retardation worsens with increase in X chromosomes
Behavior problems in Keinfelter’s syndrome
shyness
poor judgement
unrealistic, boastful activity
Dx & mgnt of Kleinfelter’s syndrome
clinical findings- karyotype
tx helpful before puberity- testosterone replacement
Williams Syndrome
deletion of allele (7q11.23)
Facial features of Williams Syndrome
short palpebral fissures
depressed nasal bridge
long philtrum
blue eyes
Clinical characteristics of Williams syndrome
supravalvular aortic stenosis motor retardation (tight heel cords) FTT IQ 40-80 friendly, loquacious personality "cocktail party" personality hypersensitive to sound renal anomalies