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MCBM Exam 5 Kat > Chromosomal Defects > Flashcards

Chromosomal Defects Flashcards

1
Q

What do ~20% of infant deaths in US results from?

A

Birth defects

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2
Q

When is the maternal serum screen (MSS) done?

A

15-20 wks gestation

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3
Q

What three malformations does MSS look for?

A

Trisomy 21
Trisomy 18
Neural tube defects

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4
Q

What levels of AFP, uE2 and hCG show in Trisomy 21?

A

AFP - low
uE2 - low
hCG - high

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5
Q

What levels of AFP, uE2 and hCG show in Trisomy 18?

A

Low in all

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6
Q

What levels of AFP, uE2 and hCG show in Neural Tube Defects?

A

AFP - high
uE2 - normal
hCG - normal

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7
Q

Define anomaly.

A

A structural defect of any type

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8
Q

Define malformation.

A

Intrinsic; genetic

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9
Q

Define deformation.

A

Extrinsic; mechanical

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10
Q

Define disruption.

A

Extrinsic; teratogen exposure

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11
Q

Define syndrome.

A

Multiple anomalies that occur independently, but are cause by a single defect

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12
Q

Define sequence.

A

When a structural or mechanical factor leads to multiple secondary effects

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13
Q

What are some general characteristics of multifactorial disorders?

A

Disorders that tend to run in families
No single gene or chromosomal abnormality is responsible
Usually a combination of genetics & environmental factors required for phenotypic expression
Do not follow Mendelian patterns of inheritance

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14
Q

What are some general characteristics of whole chromosome disorders?

A 
Usually incompatible with life
Rarely reproduce
Most directly linked to maternal age
May occur in autosomes or sex chromosomes
Detectable via karyotype analysis
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15
Q

What are some examples of Multifactorial disorders?

A 
Coronary artery disease
IDDM
Hypertension
Some forms of cancer
Some developemental defects including:
Congenital heart defects
Spina bifida
Anencephaly
Cleft palate
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16
Q

What is XXX?

A

A common abnormal karyotype also known as super female.

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17
Q

What is XO?

A

Turner syndrome

The only recognized monosomy

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18
Q

What is XXY?

A

Klinefelter syndrome

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19
Q

What is XYY?

A

A common abnormal karyotype also known as super male.

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20
Q

What are some symptoms of Klinfelter Syndrome?

A 
47, XXY
1st recognized sex chromosome abnormality
Tall
Low IQ
Infertile
Hypogonadism
Gynecomastia
21
Q

What are some symptoms of Turner Syndrome, the only true monosomy?

A 
45, XO
Short
Infertile
Normal IQ
Webbed neck
Broad chest/wide set nipples
25% mosaics
22
Q

What is fragile X syndrome?

A

An X-linked disorder that about 1/1500 males get

23
Q

What is fragile X syndrome characterized by?

A

Mild connective tissue dysplasia
Macro-orchidism
Dental crowding

24
Q

What is fragile X syndrome caused by?

A

By GCC repeats in 5’ UTR of FMR1 gene

25
Q

What are the normal, submutation and Fragile X values for the GCC repeats?

A

Normal = 29 repeats
Submutation = 29-230 repeats
Fragile X = >230

26
Q

What gene is silenced in fragile X syndrome and how?

A

FMR1 silenced via methylation

27
Q

What is trisomy 21, 18 and 13?

A 
21 = Down syndrome
18 = Edward syndrome
13 = Patau syndrome
28
Q

What are the clinical features of trisomy 21?

A 
Mental retardation
Epicanthic folds
Hypotonia
Simian creases
Short stature
Furrowed tongue
Heart defects
Predisposed for leukemia
Brush field spots on iris
Gap b/w 1st and 2nd toes
Neurofibrillary tangles
Duodenal obstruction
29
Q

What is the incidence of trisomy 18?

A

1:8000

30
Q

What are the clinical features of trisomy 18?

A 
Mental retardation
Rocker-bottom feet
Malformed ears
Hypoplastic nails
Rarely survive past infancy
31
Q

What is the incidence of trisomy 13?

A

1:25000

32
Q

What are the clinical features of trisomy 13?

A

Lethal by 6 mo
Severe CNS malformations
Often cleft lip/cleft palate
70% have holoprosencephaly

33
Q

What are the features of Cri du chat syndrome?

A 
5p deletion
Microcephaly
Micrognathia
Hypertelorism
Malformed ears
Severe retardation
34
Q

What are Robertsonian Translocations?

A

Translocations between 2 acrocentric chromosomes

35
Q

What translocation is associated with a familial form of Down Syndrome?

A

14q;21q

36
Q

What are teratogens?

A

Drugs, chemicals & infectious agents that may adversely affect fetal development

37
Q

What are important factors that affect the outcome of teratogen exposure?

A

Time of exposure
Dosage
Fetal/Maternal genotype

38
Q

What are some examples of drugs/chemicals that act as teratogens?

A

Thalidomide
Retinoic acid (Accutane)
Alcohol
Hydantoin (Dilatin)

39
Q

What do ACE inhibitors do as teratogens and at what point do they cause these problems in pregnancy?

A

kidney defects; in the 2nd and 3rd trimester

40
Q

How bad are antineoplastic agents as teratogens?

A

Severe

41
Q

What type of effects does mercury have as a teratogen?

A

Neurotoxin with cerebral-palsy like syndrome

42
Q

What is an example of a lack of a morphogen?

A

Folate which is critical for neural tube development

43
Q

What does a maternal deficiency in Vitamin A (Retinoid Acid) lead to?

A

Small eyes (microphthalmia)
Cleft palate/lip
Cardiovascular & urogenital anomalies
Malformed limbs

44
Q

What are the clinical features of Fetal Alcohol Syndrome?

A 
Major cause of mental retardation
Skeletal defects
Growth retardation
Heart Defects
Smooth philtrum
1 in 6 have cleft palate
45
Q

What are the clinical features of Fetal Hydantoin Syndrome?

A

Craniofacial anomalies
Growth retardation
Mental retardation
Limb defects

46
Q

What is the degree of severity linked to in fetal hydantoin syndrome?

A

Low activity form of epoxide hydrolase in mother

47
Q

What are the teratogenic infections?

A 
TORCH
Toxoplasmosis
Other: HIV, Syphilis, VZV
Rubella
CMV
HSV
48
Q

What symptoms may come from maternal diabetes mellitus?

A

Cardiovascular defects

CNS defects

49
Q

What symptoms may come from maternal phenylketonuria?

A

Microcephaly
Congenital heart defects
Retardation

MCBM Exam 5 Kat (15 decks)

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