Ch 16 Patterns of Anomalies Flashcards
What is a syndrome?
Pattern of multiple anomalies related to a single causative factor/pathology
(ex. a trisomy)
What is an association?
-Pattern of multiple anomalies seen in numerous individuals that is NOT related to a single factor/pathology
-NOT part of a sequence or syndrome
(ex. finding 1 malformation leads to searching for others associated with it)
What is a sequence?
Pattern of multiple anomalies that results from an initial single anomaly
(a sequence may be the result of a malformation, deformation or disruption)
What is a malformation?
Anomaly (single or multiple) where the structure or tissue is abnormal from the start
(ex. cleft lip or palate)
What is a deformation?
Anomaly that is intrinsic or extrinsic in origin
(ex. of extrinsic deformation - structure/tissue is affected by outside forces resulting in an abnormal shape or position)
What is a disruption?
-Anomaly where the structure/tissue that was previously normal breaks down as a result of some type of insult to the developmental process
-Intrinsic, extrinsic + vascular insults can cause this
(ex. amputation of extremity due to amniotic bands OR malformation due to a teratogen like rubella)
What is a dysplasia?
Anomaly where the structure of tissue lacks the normal organization of cells
(ex. congenital ectodermal dysplasia)
What is genetics?
Study of heredity in living organisms
List the 2 groups of cells in the body?
Germ cells (gametes): 23 chromosomes (haploid) - consists of 22 autosomes + 1 sex chromosome either X or Y
Somatic cells (everything else): 23 pairs/46 chromosomes (diploid) - consists of 22 pairs of autosomes + 2 sex chromosomes
Somatic cells replicate through what process?
Mitosis - produces 2 daughter cells that are diploid (46 chromosomes)
Germ cells replicate through what process?
Meiosis - produces 4 daughter cells that are haploid (23 chromosomes)
(errors with meiosis can cause abnormalities in chromosomes)
What is heteroploidy?
Changes in the # of chromosomes present in the cells (are numeric anomalies)
What is euploidy?
-Condition where there are integral multiples of haploid number of chromosomes
-Meaning all chromosomes in the cell are affected equally
(ex. triploidy)
How many chromosomes are in a triploidy?
69 (3 x 23)
What is aneuploidy?
Condition where there is a departure from the euploid number of chromosomes
(ex. having extra chromosome (trisomy) OR missing a chromosome (monosomy))
What is inheritance?
Transmission of genetic code from parents to offspring
Differentiate autosomal dominant + recessive?
Dominant: When one parent has the dominant gene there is a 50% chance each child will inherit the trait.
Recessive: When each parent carries the gene with the trait but are not affected. Each child has a 25% chance of having the trait, 50% of becoming a carrier + 25% chance of not inheriting the gene.
What does X-linked mean?
Conditions associated with genes located on X chromosome, may be dominant or recessive (m/c)
(ex. color blindness)
What is multifactorial?
Conditions can occur as both genetic + nongenetic causes (they recur in families but there is no identifiable pattern of transmission)
(ex. cardiac defects, neural tube defects + facial clefting)
List 3 R/F’s for chromosomal abnormalities?
-Maternal age (>35) + paternal age (>40-45)
-Previous pregnancy with chromosomal abnormality
-History of early pregnancy loss
1st trimester prenatal screening is for assessing the risk for what?
Trisomy 13, 18 + 21
An increase in hCG, decrease in PAPP-A + increase in NT are associated with which trisomy?
Trisomy 21 (down syndrome)
In 2nd trimester, what 4 biochemical markers are used for prenatal screening?
MSAFP, hCG, unconjugated estriol (uE3) + inhibin A
MSAFP + uE3 are low while hCG + inhibin A are elevated in which trisomy?
Trisomy 21
What is beckwith-weidemann syndrome (BWS)?
-Overgrowth disorder
5 findings:
Macroglossia, anterior wall defects, hypoglycemia at birth, macrosomia + hemihpyperplasia
Name 1 feature of BWS?
Facial nevus flammeus (a pink or red patch on newborn’s skin)
Which chromosome does BWS affect?
Chromosome 11 (m/c autosomal dominant)
What is the classic sonographic finding in BWS?
-Macroglossia + trisomy 21
What is meckel-gruber syndrome?
Rare + characterized by renal dysplasia, limb anomalies + encephalocele
(1:1 ratio in males to females)
Is meckel-gruber syndrome m/c autosomal dominant or recessive?
Recessive - is linked to multiple chromosomes
List the 3 classic findings of meckel-gruber syndrome?
-Enlarged echogenic kidneys (100%)
-Polydactyly (55-75%)
-Occipital encephalocele (60-80%)
(oligohydramnios + absent bladder also seen due to lack of urine production)
Do babies with meckel-gruber syndrome live?
No, don’t survive more than few fays due to renal malformations
What is turner syndrome also called?
Monosomy X (45 XO)
What is turner syndrome?
Absence of 1 of the 2 sex chromosomes
(m/c missing sex chromosome from the paternal contribution)
Does turner syndrome only affect males or females?
Females
Cause of turner syndrome (monosomy X)?
A sporadic event of a nondisjunction error occurring at gametogenesis
What is the classic sonographic finding of turner syndrome?
A cystic hygroma (bulge at neck)
What is potter sequence?
Describes the typical physical appearance caused by pressure in utero due to oligohydramnios
Oligohydramnios may be caused by what 3 things?
-Renal anomalies
-Amniotic leakage
-Placental anomalies
Diminished amniotic fluid volume impairs what?
Normal development of fetal structures + results in deformities of extremities, facial features (potter facies) + pulm hypoplasia
What are other synonyms for potter sequence?
Potter syndrome + oligohydramnios syndrome are used interchangeably
What is triploidy?
Presence of a complete extra set of chromosomes
(3% survival rate)
99% of triploidy’s are due to what?
-2 sperms fertilizing 1 egg (diandry)
OR
-From an extra chromosome set from the mother (digyny)
What type of thickening can be seen in 1st trimester when triploidy is present?
NT thickening
Differentiate what will occur if the mother vs father contributes the extra chromosomes with triploidy?
Mother: fetus with asymmetric IUGR + small placenta
Father: fetus with symmetric IUGR + large placenta (partial hydatidiform mole)
What is the m/c combination of findings with triploidy?
Ventriculomegaly + syndactyly of the 3rd/4th digtis
What are the alternate names for trisomy 13, 18 + 21?
13: patau
18: edward
21: down
What is trisomy 13?
-Chromosomal condition with a pattern of malformations that cause intrauterine + neonatal death
-Often due to advanced maternal age
Does the triple or quadruple screening in the 2nd trimester show some benefit when looking for trisomy 13?
Quadruple - increased AFP in presence of a CNS or ventral wall defect
Is the extra set of chromosomes with trisomy 13 inheritable?
No, it is a random event that is noninheritable
What is a mosaic trisomy 13?
A person with the extra chromosome in some of his/her cells
Is it easy to identify a fetus with trisomy 13 with u/s?
Yes - NT thickening in 1st trimester + multiple major anomalies seen in 2nd trimester (hard to miss)
Do most trisomy fetuses survive to birth?
Yes - but most die after birth
What is the 2nd m/c trisomy that can carry to term?
Trisomy 18 (m/c female)
Does virtually every organ system have identifiable sonographic markers in associated with trisomy 18?
Yes:
-1st trimester NT thickening is greater than with trisomy 21
-Strawberry shaped skull
-ASD + VSDs
-Clenching of hands
A combination of what 3 things is highly predictive of trisomy 18 in 3rd trimester?
-Abnormal hand posturing
-IUGR
-Polyhydramnios
(intrauterine death is common - but if fetus survives they will have profound mental + physical disabilities)
What is the m/c pattern of malformation in man?
Trisomy 21 (found by John Langdon Down in 1866)
Is there a single screening test that identifies trisomy 21?
Nope
Trisomy 21 is m/c due to what 2 things?
-Maternal nondisjunction 95% of time (occurs when chromosomes fail to segregate during meiosis)
-Advanced maternal age
Can trisomy 21 be inherited?
No - is random event in classic + mosaic forms
Trisomy 21 fetuses are reported to have what findings?
-Cardiac defects
-Shortened humerus
-Thickened NF
-Absent/hypoplastic NB
-Shortened femur
-Mild pyelectasis
-Echogenic bowel
-Echogenic intracardiac focus
(only 25% of fetuses have detectable major anomalies in 2nd trimester)
What is the highest level of sensitivity + specificity in identifying down syndrome in a fetus?
By identifying a cluster of markers, rather than just 1 finding
What is the median life span for people with trisomy 21?
49 years - due to cardiac defects
What is VATER/VACTERL association?
-Collection of anomalies that include vertebral defects, anal atresia, TE fistula + renal anomalies
-A complex condition that affects several parts of the body.
-Is an acronym that stands for the affected parts of the body including the vertebrae, anus, heart, trachea, esophagus, kidney and limbs.
VATER/VACTERL is associated with X or Y linked chromosomes?
X-linked + is autosomal recessive
Can VATER/VACTERL occur in a normal child?
Yes - or in children with chromosomal abnormalities
Do most people with VATER/VACTERL association survive?
Yes - most get surgical correction + rehabilitation
