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MBBS 3: Pediatrics > Genetics > Flashcards

Genetics Flashcards

1
Q

What is malformation?

A

Structural defect due to localized error in morphogenesis resulting in the abnormal formation of a tissue or organ

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2
Q

Dysplasia?

A

abnormal organization of cells into tissues

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3
Q

Deformation?

A

alteration in shape or structure of a structure or organ that has developed or differentiated normally

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4
Q

Disruption?

A

defect resulting from the destruction of a structure that had formed normally before the insult

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5
Q

Sequence?

A

Single error in morphogenesis that results in a series of subsequent defects
e.g. Pierre-Robin sequence, in which a small jaw results in glossoptosis and cleft palate

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6
Q

Deformation sequence?

A

Mechanical (uterine) force that alters structure of intrinsically normal tissue
e.g. Oligohydramnios produces deformations by in utero compression of limbs (e.g., dislocated hips, clubfoot), crumpled ears, or small thorax

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7
Q

Disruption sequence?

A

In utero tissue destruction after a period of normal morphogenesis
e.g. Amnionic membrane rupture sequence, leading to amputation of fingers/toes

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8
Q

Malformation syndrome?

A

Multiple malformations in unrelated tissues with a known unifying cause
e.g., Trisomy 21, Teratogens, other syndromes

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9
Q

Association?

A

An association is a pattern of malformations that occurs together too frequently to be due to random chance alone but for which no specific etiology is yet recognized

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10
Q

Neural tube defects?

A

failure of the neural tube to close spontaneously between the 3rd and 4th week of in utero development.

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11
Q

Epidemiology of Down syndrome?

A
  • Incidence approximately 1 in 733 live births
  • The risk is highest in women who conceive after age 35 year
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12
Q

What causes Down syndrome?

A
  1. Approx. 95% have 3 copies of chromosome 21 (error in meosis)
  2. Approx. 1% of persons are mosaics
  3. Approx 4% have atranslocationinvolving chromosome 21
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13
Q

What is meiotic nondisjunction in Trisomy 21?

A
  • the chromosome 21 pair fails to separate so that on gamete has 2 chromosome 21s and one has none
  • fertilization of the gamete with 2 chromosome 21s give rise to a zygote with trisomy 21
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14
Q

What is the translocation that causes trisomy 21?

A

when the extra chromosome 21 is joined onto another chromosome (usually 14 but can also be 15, 22, or 21)

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15
Q

What is mosaicism in Trisomy 21?

A

some of the cells are normal and some have trisomy 21

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16
Q

Associated congenital cardiac defects in Down syndrome?

A
  1. Atrioventricular septal defects
  2. Ventricular septal defects
  3. Isolated atrial septal defects
  4. Patent ductus arteriosus
  5. Tetralogy of Fallot
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17
Q

Pulmonary complications with Down syndrome?

A
  1. Recurrent respiratory infections
  2. Sleep-disordered breathing
  3. Laryngo- and tracheobronchomalacia
  4. Pulmonary hypertension
  5. Asthma
18
Q

Other anomalies associated with DS?

A
  1. Congenital gastrointestinal anomalies
  2. Hypothyroidism
  3. Leukemia
  4. Immune dysfunction
  5. Diabetes mellitus
  6. Seizures
  7. Alopecia
  8. Juvenile idiopathic arthritis
  9. Problems with hearing and vision
  10. Alzheimer disease–like dementia (4th decade)
19
Q

GI anomalies associated with Down syndrome?

A
  1. Duodenal atresia
  2. Hirschsprung disease
  3. omphalocele
  4. imperforate anus
  5. cholelithiasis
20
Q

Clinical features of Down syndrome?

A
  1. Up-slanting palpebral fissures, epicanthal folds, and flat nasal bridge
    - Anepicanthal foldis a skinfoldof the upper eyelid covering the inner corner of the eye
  2. Brushfield spots - Small, white or greyish/brownspotson the periphery of theiris
  3. Bridged palmar crease - Two transverse palmar creases are connected by a diagonal line
  4. Wide space between first and second toes
  5. Short fifth finger
  6. Small ears
  7. flat occiput
  8. infants are usually hypotonic
21
Q

Typical craniofacial appearance of Down syndrome?

A
  1. round face and flat nasal bridge
  2. upslanted palpebral fissures
  3. epicanthic folds
    - a fold of skin running across the inner edge of the palpebral fissure
  4. Brushfield spots in iris
    - pigmented spots
  5. small mouth and protruding tongue
  6. small ears
  7. flat occiput and third fontanelle
22
Q

Later medical problems?

A
  1. delayed motor milestones
  2. learning difficulties
  3. short stature
  4. increased susceptibility to infections
  5. hearing impairment from secretory otitis media
  6. visual impairments from cataracts, squints, myopia
  7. increased risk of leukemia and solid tumors
  8. acquired hip dislocation and atlantoaxial instability
  9. obstructive sleep apnea
  10. increased risk of hypothyroidism and coeliac disease
  11. epilepsy
  12. early onset Alzheimer disease
23
Q

What is Turner syndrome?

A

Structural or numeric aberrations of the X chromosomes

24
Q

Clinical features of Turner syndrome?

A
  1. Short stature
  2. Delayed puberty due to gonadal failure
  3. Wide carrying angle (cubitus valgus)
  4. Shieldlike chest
  5. Webbed neck
  6. Aortic valve stenosis, aortic coarctation, aortic dilation and rupture
25
Q

How to determine inheritance?

A
26
Q

What is hemopilia?

A

X-linked bleeding disorder

27
Q

Types of Hemophilia?

A

Hemophila A: Deficiency of factor VIII
Hemophilia B: Deficiency of factor IX
Hemophilia C: Deficiency of factor XI

28
Q

Epidemiology of hemophilia?

A

Hemophilia A occurs in roughly 1 per 5000 live male births
Hemophilia B affects 1 in 30,000

29
Q

Etiology of hemophilia?

A
  • The genes for factor 8 and factor 9 are on the X chromosome are affected
  • The lack of factor 8 or factor 9 delays the generation of thrombin, which is crucial to forming a normal, functional fibrin clot and solidifying the platelet plug that has formed in areas of vascular injury
  • The severity of the disorder is determined by the degree of clotting factor deficiency
30
Q

What is the chance of transmission from a female carrier to her sons?

A

50%
- With only one copy of the X chromosome, males are more likely to manifest these diseases than females. Each son born to a female carrier of an X-linked recessive trait has a 50% chance of inheriting the trait, but none of this woman’s daughters would be expected to be affected (each daughter has a 50% chance of being a carrier)

31
Q

What is the risk of transmitting the affected gene from the father to his sons?

A

0%
- An affected father transmits the mutation to all his daughters, who are carriers, but not to his sons; having received their father’s Y chromosome, they would not be affected (thus there is no male-to-male transmission.

32
Q

Diagnosis of hemophilia A and B?

A
  1. Suggested by Prolonged aPTT
  2. Confirmed by specific assays for either factor VIII or IX
33
Q

What is hypothyroidism?

A
34
Q

What are the types of hypothyroidism?

A
  1. primary
  2. secondary
35
Q

What is primary hypothyroidism?

A

Thyroid dysgenesis (80-85%) e.g., agenesis, hypoplasia, ectopia.
Defects in thyrotropin (TSH) responsiveness
[(e.g., TSH receptor-blocking antibodies, Mutation in TSH receptor (TSHR)]
Defect in thyroid hormone synthesis (dyshormonogenesis)
Iodine deficiency (endemic goiter
Maternal medications (e.g., methimazole, propylthiouracil)

36
Q

What is secondary hypothyroidism?

A

Isolated TSH deficiency (e.g., Mutation in TRH receptor)
Multiple pituitary hormone deficiencies

37
Q
A
38
Q

What is Pendred syndrome?

A

is an autosomal recessive disorder composed of sensorineural deafness and goiter
Pendred syndrome is caused by a mutation in the chloride–iodide transport protein pendrin(SLC26A4)that is expressed in the thyroid gland and the cochlea

39
Q

Clinical manifestation of hypothyroidism?

A

Wide anterior and posterior fontanels at birth
Prolonged jaundice (indirect hyperbilirubinemia)- delayed maturation of hepatic glucuronide conjugation
Cry little, sleep much, have poor appetites, and are generally sluggish
Feeding difficulties, sluggishness, lack of interest, somnolence, and choking spells during nursing
Respiratory difficulties, partly caused by macroglossia
Noisy respirations, and nasal obstruction
Constipation that does not usually respond to treatment
Large abdomen, umbilical hernia
Subnormal temperature
Cold skin on the extremities
Edema of the genitals and extremities
Low pulse

40
Q
A

MBBS 3: Pediatrics (40 decks)

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