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Adv Pathophysiology > Chapter 5: Genetic & Congenital Disorders > Flashcards

Chapter 5: Genetic & Congenital Disorders Flashcards

1
Q

Congenital Defects (Birth Defects)

A

abnormalities of body structure, function, or metabolism that are present at birth
leading cause of infant death

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2
Q

Gene mutation

A

a biochemical event that produces a new allele for a particular gene
a single mutant gene may be expressed in many different areas of the body (i.e. Marfan syndrome)

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3
Q

Single Gene Disorders

A

defect of a mutant allele at a single gene locus

follow a Mendelian pattern of inheritance

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4
Q

Mendelian Patterns of Inheritance

A

depend on:
whether phenotype is dominant or recessive
whether gene is an autosomal or sex chromosome

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5
Q

Types of Single Gene Disorders

A

Autosomal Dominant
Autosomal Recessive
X-Linked Disorders

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6
Q

Autosomal Dominant Disorders

A

single mutant allele from affected parent = 50% change of passing gene to offspring regardless of sex
Examples:
Marfan Syndrome
Neurofibromatosis 1 and 2 (NF-1 and NF-2)
Huntington chorea

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7
Q

Penetrance

A

chance that a person who inherited the defective gene will express it (a percentage)

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8
Q

Variable Expressivity

A

extent of variation in phenotype (mild to severe)

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9
Q

Co-dominant Genes

A

alleles are different but both genes are expressed (i.e. AB blood type)

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10
Q

MARFAN SYNDROME

Autosomal Dominant Disorder

A

inherited disorder of the connective tissue, mutations on chromosome 15 that codes for Fibrillin I (component of connective tissue)
average lifespan 30-40 years

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11
Q

Clinical Manifestations of MARFAN SYNDROME

A

tall, thin, long extremities with joint hypermobility
arachnodactyly
cataracts, lens dislocation, retinal detachments, myopia
valvular abnormalities (MVP, aortic regurg)
spontaneous pneumothorax

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12
Q

Arachnodactyly

A

“spider-like” appearance of fingers and toes; seen in someone with Marfan Syndrome

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13
Q 
NEUROFIBROMATOSIS 1 (von Recklinghausen disease)
(Autosomal Dominant Disorder)
A

most common autosomal dominant disorder caused by a genetic defect in the tumor suppressor gene (NF-1) located on chromosome 17
100% penetrance - variable expressivity

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14
Q

Clinical Manifestations of NF-1

A

Neurofibromas
Cafe-au-lait spots
Benign pigmented nodules on iris (Lisch nodules)
learning and speech disabilities - ADD - seizures

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15
Q

Neurofibromas

NF-1

A

benign peripheral tumors of the nerves
Cutaneous: soft, pedunculated lesions projecting from the skin
Subcutaneous: firm, round, painful
vary in number

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16
Q

Lisch nodules

NF-1

A

benign pigmented nodules on iris

present after age 6 years

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17
Q 
NEUROFIBROMATOSIS 2 (Acoustic NF)
(Autosomal Dominant Disorder)
A

characterized by tumors of the acoustic nerve (CN VIII) - gene is located on chromosome 22
asymptomatic first 15 years of life

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18
Q

Clinical Symptoms of NF-2

A

headaches, hearing loss, tinnitus
worsens with pregnancy and oral contraceptives
severe disorientation may occur during diving or swimming underwater (drowning may result)

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19
Q

HUNTINGTON CHOREA

Autosomal Dominant Disorder

A

neurodegenerative disorder where basal ganglia are destroyed caused by mutation on chromosome 4
age-dependent penetrance (between 30 and 50 years)
100% penetrance

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20
Q

Clinical Manifestations of HUNTINGTON CHOREA

A 
cognitive decline
mood swings
involuntary movements
hallucinations
speech difficulties
behavioral and personality changes
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21
Q

Autosomal Recessive Disorders

A

manifested only when BOTH genes are affected (homozygous)
occurence risks: 25% affected, 50% carriers, 25% unaffected
“loss of function” mutation - includes most inborn errors of metabolism
Examples: PKU, Tay-Sachs disease, sickle cell disease, cystic fibrosis

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22
Q

PHENYLKETONURIA (PKU)

Autosomal Recessive Disorder

A

inborn error of metabolism of the amino acid phenylalanine - lack activity of phenylalanine hydroxylase
results in cerebral damage and intellectual disability
irreversible damage usually complete by age 2 or 3 years
more common in Caucasians and Native Americans

23
Q

Phenylalanine hydroxylase

A

liver enzyme that converts phenylalanine to tyrosine

lacking in PKU, causing phenylalanine accumulation in blood and urine leading to cerebral damage

24
Q

Clinical Manifestations of PKU

A

symptoms are gradual and difficult to assess - screen ALL infants
mental retardation
personality and behavior disturbance (antisocial or uncontrolled temper)
seizures - hyperactivity, irritability, repetitive motions
microcephaly - slowed growth
eczematous skin lesions or rough skin
musty odor from skin and urine

25
Q

TAY-SACHS DISEASE

Autosomal Recessive Disorder

A

results from a congenital enzyme deficiency (hexosaminidase A) causing lipids to accumulate in organs and demyelinate and destroy CNS cells
progressive mental and motor deterioration
fatal before age 5
more common in those of Jewish ancestry

26
Q

Hexosaminidase A

A

enzyme necessary for metabolism of GM2 (glycolipids found in tissues of the CNS)
deficiency in Tay-Sachs disease causes GM2 to accumulate in the lysosomes

27
Q

Clinical Manifestations of TAY-SACHS DISEASE

6 to 12 months

A 
appearance of symptoms - progressive weakness of all muscles
unable to sit up or lift head
trouble turning over
cannot grasp objects
vision loss progressing to blindness
28
Q

Clinical Manifestations of TAY-SACHS DISEASE

by age 18 months

A

Seizures
generalized paralysis and spasticity
decerebrate rigidity and complete vegetative state follows

29
Q

Clinical Manifestations of TAY-SACHS DISEASE

age 2+ years

A

vegetative state
recurrent bronchopneumonia
treatment is supportive
usually fatal by age 5 years

30
Q

SICKLE CELL DISEASE

Autosomal Recessive Disorder

A

disease of the beta subunit of hemoglobin (HbS) - mutation of gene on chromosome 11
hemoglobin does not form correctly and RBCs become rigid and die early
more common in African Americans (1 in 365)

31
Q

Clinical Manifestations of SICKLE CELL DISEASE

A

“sickled” RBCs can cause obstruction and reduced perfusion/ischemia
impaired oxygenation
pain

32
Q

X-Linked Dominant Disorders

A

lethal in embryonic males or the homozygous mutant females
heterozygous affected females transmit disorder to 50% of offspring (regardless of sex)
affected males will have 100% affected daughters or 100% normal sons
Example: Fragile X Syndrome

33
Q

FRAGILE X SYNDROME

X-Linked Dominant Disorder

A

most common form of inherited intellectual disability
mapped to the long arm (q) of the X chromosome (Xq27)
designated as the Fragile X Mental Retardation 1 (FMR-I) site
affects males > females

34
Q

Characteristics of FRAGILE X SYNDROME

A 
intellectually disabled
long face with large mandible
large ears/high arched palate
hyperextensible joints
mitral valve prolapse
large testes
35
Q

X-Linked Recessive Disorders

A

Most X-linked disorders are recessive
Each son of affected mother has 50% chance of being affected
Daughters have 50% chance of being carriers
100% of daughters of affected males will be carriers
Example: Hemophilia A

36
Q

HEMOPHILIA A

X-Linked Recessive Disorder

A

bleeding disorder inherited from mother due to factor VIII deficiency - mutation on F8 gene on X long arm (q)
treatment with replacement therapy
affected males will transmit the gene to all of their daughters and none to their sons

37
Q

Multifactorial Disorders

A

caused by multiple genetic mutations and environmental factors and teratogens
can be congenital or expressed later in life

38
Q

Multifactorial Congenital Disorders

A

Cleft lip and cleft palate
Clubfoot/congenital dislocation of the hip
Pyloric stenosis
Congenital heart disease

39
Q

Multifactorial Disorders Occurring Later in Life

A

CAD
HTN
DM
Cancer

40
Q

CLEFT LIP and CLEFT PALATE

Multifactorial Congenital Disorders

A 
cleft lip (with or without) cleft palate it one of the most common birth defects originates around 35th day of gestation; results in distorted facial appearance
nutritional intake speech are affected
commonly have hearing problems from middle ear damage/infections
41
Q

Treatment of CLEFT LIP/CLEFT PALATE

A

special bottle/nipples for feeding (palate)
surgery: lip by 3 months of age, palate before 1 year
speech therapy

42
Q

Chromosomal Disorders

A

described according to the description of the karyotype
result in large proportions of early miscarriages, congenital malformations, and intellectual disability
Examples: Down Syndrome (Trisomy 21), Turner’s Syndrome (monosomy, XO), Klinefelter’s Syndrome (Trisomy, XXY)

43
Q

Trisomy 13, 18, and 21

A

the only chromosomal trisomies that can result in term pregnancy
trisomy on any other chromosome result in death or spontaneous abortion

44
Q 
DOWN SYNDROME (Trisomy 21)
(Chromosomal Disorder)
A

chromosomal aberration in which chromosome 21 has 3 copies vs. 2; most commonly caused by nondisjunction
most common chromosomal disorder that produces intellectual disability, characteristic facial features, and distinctive physical abnormalities
extra chromosome originates in mother in 90% of cases (risk increases with maternal age)

45
Q

Physical Signs of Down Syndrome

apparent at birth

A

small, square head with flattened face and small nose
small open mouth and protruding tongue
low-set ears, upward slanted eyes with epicanthal folds
short fingers w/ transverse crease on palm
Brushfield’s spots and cataracts

46
Q

TURNER’S SYNDROME (45, XO)

Sex Chromosome Disorders

A

most frequently occuring genetic disorder in females

absence of all or part of the X chromosome (less feminine)

47
Q

Characteristics of TURNER’S SYNDROME (45, XO)

A

short stature and underdeveloped breasts
no secondary sex characteristics
treated with growth hormone and estrogen therapy

48
Q

KLINEFELTER’S SYNDROME (47, XXY)

Sex Chromosome Disorder

A

presence of >1 X chromosome in excess of the normal male XY complement
results from nondisjunction
extra X (extra feminine)

49
Q

Characteristics of KLINEFELTER’S SYNDROME (47, XXY)

A

enlarged breasts
small testes and inability to produce sperm
sparse body hair
tall stature
feminine distribution of SQ fat
treatment through PT/SLP; androgen therapy

50
Q

Period of vulnerability

A

day 15 to day 60 after conception
embryo’s development is most easily disturbed during the period when differentiation and development of the organs (organogenesis) is taking place

51
Q

Teratogens

A

a substance, organism, physical agent, or deficiency state present during gestation capable of causing adverse effects

52
Q

Fetal Alcohol Syndrome

A

group of physical, behavioral, and cognitive abnormalities caused by harmful effects of alcohol throughout pregnancy
effects vary widely
commonly see growth retardation, neurologic abnormalities (behavioral, developmental)
small palpebral fissures and smooth philtrum (upper lip)

53
Q

Infectious Teratogens: TORCH

A 
T = Toxoplasmosis
O = Others (syphilis, parvovirus B19, varicella)
R = Rubella
C = Cytomegalovirus
H = Herpes simplex 2, HIV, Hep B & C
54
Q

Folic Acid Deficiency

A

implicated in the development of neural tube defects

recommended all women of childbearing age receive 400mcg (0.4 mg) of folic acid daily

Adv Pathophysiology (22 decks)

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