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Y2 GENETICS IN MEDICINE > Dysmorphology > Flashcards

Dysmorphology Flashcards

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1
Q

What is the definition of morphology?

A

the scientific study of the structure and form of either animals and plants or words and phrases

this usually involves features in the face

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2
Q

At what stage of life is diagnosis of a dysmorphic condition usually easiest and why?

A

diagnosis is easier in children than in babies and adults

this is because features change with age

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3
Q

What % of births are affected by a congenital malformation?

A

2-3% of births

single malformations are often isolated events

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4
Q

What things suggest that a congenital malformation is likely to be genetic?

A
  1. if there are multiple malformations
  2. dysmorphic
  3. family history of similar problems
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5
Q

Why is it important to detect dysmorphology?

A

it assists in making a diagnosis

this diagnosis guides prognosis, management and recurrence risk

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6
Q

What type of abnormality is present in DiGeorge syndrome?

A

22q11.2 deletion

deletion of a small part of chromosome 22 near the middle of the chromosome at a location known as q11.2

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7
Q

Approximately how many births are affected by a 22q11.2 deletion?

What symptoms are present in most patients with this deletion?

A

affects around 1 in 5,000 births

symptoms are very variable but most patients have:

  1. hypocalcaemia
  2. seizures
  3. immune deficiency
  4. renal malformation
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8
Q

What symptoms are present in some patients with DiGeorge syndrome, but not all?

A
  1. 70% have learning difficulties
  2. 15% have cleft palate
  3. 32% have velopharyngeal insufficiency
  4. 75% congenital heart defects
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9
Q

What is achondroplasia?

Around how many births are affected by this condition?

A

a bone growth disorder that causes disproportionate dwarfism

it affects around 1 in 20,000 people

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10
Q

What are the typical features visible in a person with achondroplasia?

A
  1. rhizomelic limb shortening
  2. short stature
  3. foramen magnum compression/hydrocephaly
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11
Q

What is meant by “rhizomelic” limb shortening?

A

Rhizomelia refers to a disproportion of the length of the proximal limb

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12
Q

What is meant by a foramen magnum compression?

What can this lead to?

A

the foramen magnum is a hole at the base of the skull, through which brainstem and spinal cord pass

compression leads to a “kink” in the brainstem, which can cause sleep apnea

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13
Q

what often causes achondroplasia?

A

it is autosomal dominant and is usually caused by a new mutation

risk increases with paternal age

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14
Q

What is meant by Beckwith-Wiedemann syndrome?

A

it is an overgrowth syndrome usually present at birth

it is characterised by an increased risk of childhood cancer and certain congenital features

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15
Q

How many births are affected by Beckwith-Wiedemann syndrome?

What is there an increased risk of in this condition?

A

1 in 10,000

there is an increased risk of Wilms tumour (nephroblastoma - a rare kidney cancer)

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16
Q

What features are seen in someone with Beckwith-Wiedemann syndrome?

A
  1. large tongue
  2. ear pits/creases
  3. exomphalos
  4. hemihypertrophy
  5. neonatal hypoglycaemia
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17
Q

What is meant by exomphalos?

A

there is a weakness in the abdominal wall where it joins to the umbilical cord

this allows abdominal contents (mainly bowel & liver) to protrude outside of the abdominal cavity

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18
Q

What is meant by ‘hemihypertrophy’?

A

a condition in which one side of the body (or part of it) is larger than the other to an extent considered greater than the normal variation

19
Q

Approximately how many births are affected by Down’s syndrome?

A

1 in 800

20
Q

What are the typical visible features associated with Down’s syndrome?

A
  1. single palmar crease
  2. cataracts
  3. hypotonia in neonates
21
Q

What other diseases/conditions is Down’s syndrome associated with?

A
  1. congenital heart disease
  2. hypothyroidism
  3. hearing impairments
  4. leukaemia
  5. alzheimer’s disease
22
Q

What is meant by hypotonia in Down’s syndrome?

A

the presence of decreased muscle tone

23
Q

What is meant by a single palmar crease in Down’s syndrome?

A
24
Q

What is meant by atlanto-axial instability in Down’s syndrome?

A

excessive movement at the junction between the atlas (C1) and axis (C2) as a result of either a bony or ligamentous abnormality

25
Q

What condition is shown by this karyotype?

A

Down’s syndrome

(trisomy 21)

26
Q

Approximately how many births are affected by Kabuki syndrome?

A

1 in 30,000

27
Q

What are the typical symptoms associated with Kabuki syndrome?

A
  1. learning difficulties
  2. congenital heart disease (50%)
  3. poor growth
  4. hearing impairment
  5. cleft palate
  6. premature breast development
  7. persistent fetal finger pads
28
Q

What is meant by mosaicism?

A

when a person has 2 or more genetically different sets of cells in his or her body

29
Q

How can a diagnosis of mosaicism be made?

What lines are significant in this condition?

A

mosaicism may follow Blaschko’s lines

these are lines of normal cell development in the skin

diagnosis often requires a skin biopsy

30
Q

What is Peutz-Jeghers syndrome?

A

an autosomal dominant condition associated with the development of benign hamartomatous polyps in the gastrointestinal tract and hyperpigmented macules on the lips and oral mucosa (melanosis)

31
Q

How many people are affected by Peutz-Jeghers syndrome?

A

<1 in 50,000

32
Q

What are the complications associated with gastrointestinal polyps in Peutz-Jeghers syndrome?

A

bleeding and obstruction

33
Q

What malignancies are associated with Peutz-Jeghers syndrome?

A
  1. colorectal
  2. gastric
  3. pancreatic
  4. breast
  5. ovarian
34
Q

Approximately how many people are affected by Treacher-Collins syndrome?

A

1 in 50,000

35
Q

What is Treacher-Collins syndrome?

A

an autosomal dominant condition characterized by deformities of the ears, eyes, cheekbones, and chin

36
Q

What are the typical symptoms associated with Treacher-Collins syndrome?

A
  1. cleft palate
  2. hearing impairment
37
Q

What is Waardenburg syndrome?

A

Waardenburg syndrome is a rare genetic disorder most often characterized by varying degrees of deafness, minor defects in structures arising from the neural crest, and pigmentation changes

38
Q

Approximately how many people are affected by Waardenburg syndrome?

A

1 in 250,000

39
Q

What are the signs and symptoms associated with Waardenburg syndrome?

A
  1. sensorineural hearing impairment
  2. iris heterochromia
  3. premature greying
  4. white forelock
  5. areas of skin hypopigmentation
  6. congenital malformations (Hirschprungs/VSD)
40
Q

What is meant by iris heterochromia?

A

a condition in which the iris in one eye has a different color than the iris of the other eye

41
Q

What causes William’s syndrome?

Approximately how many people are affected?

A

7q11 deletion

affects 1 in 20,000

42
Q

What are the signs and symptoms associated with William’s syndrome?

A
  1. learning difficulties
  2. ‘cocktail party’ speech
  3. congenital heart disease
  4. hypercalcaemia
43
Q

What types of congenital heart disease are seen in William’s syndrome?

A
  1. supravalvular aortic stenosis
  2. peripheral pulmonary artery stenosis

Y2 GENETICS IN MEDICINE (11 decks)

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