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25 Cards in this Set

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What is the difference between a malformation, a deformation and a developmental field defect
Deformation: A change from the normal size or shape of an anatomic structure due to mechanical forces that distort an otherwise normal structure. occur most often late in pregnancy or during delivery. A twin pregnancy can cause deformations due to crowding of the twins late in pregnancy. ex)molding of the head of a baby born by vaginal delivery. There are usually no significant lasting effects.

A deformation is different from a malformation in timing and impact. In a malformation, the development of a structure is arrested, delayed, or misdirected early in embryonic life and the effect is permanent.

field defect is when there is disturbed development of a related group of cells in the embryo ex) bowel and bladder anomalies associated with sacral agenesis
fertilization of haploid egg by two sperm
fertilization of diploid egg due to maternal non-disjunction
fertilization of egg by a diploid sperm
what are causes of triploidy?
mosaicism, diandry digyny dispermy
One or a few chromosomes above or below the normal chromosome number.
trisomy 21
clinical features
frequency - 1/1000, 2% are mosaics, 3-4% are translocations

clinical features - hypotonia (low muscle tone), single palmar crease, congenital heart disease, extra nuchal folds, small, delayed development

Complications: hypothyroidism, seizures, leukemia, shortned lifespan, hyperbilirubinemia in neonatal period
Trisomy 18 (edwards syndrome)
Clinical features
Frequency: 1/6600, aneuploid instances are age-related

Clinical features - growth retardation, congenital malformations (cleft lip, heart, esophogeal atresia, renal malformations) hypotonia at first, hypertonia and mental retardation in survivors,
80% don't survive first year
Trisomy 13 Patau Syndrome
Clinical features
Frequency: 1/8000
anueploid patients assoc with older age

Clinical: microcephaly, holoprosencephly, microphthalmia (small eyes), mental retardation, 95% deceased by age 3
NOTE rates of trisomies are greater at conception than they are at birth b/c a lot of them die before they are birthed, so a woman has a higher risk of conceiving a trisomy baby than she has of actually having a trisomy baby
Turner Syndrome 45 x
Frequency: 1/5000
not related to maternal age

Clinical features:
ovarian dysgenesis(lack of development, ammenhorea, sterility), extra nuchal folds, short webbed neck, widley spaced nipples, coarctation of the aorta( horshoe kidneys)

Complications: diabetes, hypertension specific learning disabilities, short
Kleinfelters XXY

Small testicles, sterility, tall, gynecomastia, specific learning disabilities, behavior/emotional problems
XYY male

tendency for tall stature, educational difficulties, radial ulnar syntosis
what is the most common cause of trisomies?
maternal meiotic nondisjunction, mostly in mei 1
what diseases have risk increase with maternal age
trisomy 13 in aneuploid patients (not mosaics and translocation
trisomy 18 in aneuploid
in turner syndrome is matenal or paternal non disjunction more commonly the cause?
paternal nondisjunction in most frequently the cause
are most trisomic infants born to over or under 35
under 35, because most women have children under this age
Cri-Du-Chat 5p-
freq: 1/20,000
mech: de novo or translocation
clinical: microcephaly, weak cry
how do you detect a microdeletion?
high resolution banding
if still too small, use FISH, can't just send blood for analysis, must specify which FISH probe according to the syndrome you want to use
paternal chromosome 15 has a deletion
cause of prader willi
maternal chromosome 15 has a deletion
cause of angelmans
the disturbance of two or more unrelated henes in a chromosomal region to produce a consistent and recognizable phenotype
contiguous gene syndromes ie prader willi
general indications for chromosomal analysis
SGA, microencephaly, mental retardation, malformations, hypotonia, or those with symptoms who dont fit a standard single gene syndrome, still birth or neonatal death
who should get chromosomal analysis
parents of a dysmorphic chille out balanced, 3 or more reproductive losses, persons of any age with reproductive difficulties
anytime you see monosomy or partial trisomy what should you do
study the parents to rule out balanced translocation