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4th year passmedicine by topic > Genetics Child Health > Flashcards

Genetics Child Health Flashcards

1
Q

Autosomal recessive conditions are often thought to be ‘metabolic’ as opposed to autosomal dominant conditions being ‘structural’

A

True

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2
Q

The following conditions are autosomal dominant

A

Huntington’s disease
Myotonic dystrophy
Osteogenesis imperfecta
Von Willebrand’s disease - except T3

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3
Q

The following conditions are autosomal recessive

A

Cystic fibrosis
Gilbert’s syndrome
Haemochromatosis
Sickle cell anaemia

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4
Q

In X-linked recessive inheritance only males are affected

A

true

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5
Q

In X-linked recessive inheritance only males are affected - exception

A

Turner’s syndrome, who are affected due to only having one X chromosome

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6
Q

X-linked recessive
Each male child of a heterozygous female carrier has a ?% chance of being affected whilst each female child of a heterozygous female carrier has a ?% chance of being a carrier.

A

Each male child of a heterozygous female carrier has a 50% chance of being affected whilst each female child of a heterozygous female carrier has a 50% chance of being a carrier.

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7
Q

X-linked recessive - possibility of an affected father having children with a heterozygous female carrier is generally speaking extremely rare

A

true
However, in certain Afro-Caribbean communities G6PD deficiency is relatively common and homozygous females with clinical manifestations of the enzyme defect are seen.

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8
Q

The following conditions are inherited in a X-linked recessive fashion

A

Duchenne muscular dystrophy
G6PD deficiency
Haemophilia A,B

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9
Q

The following conditions are inherited in a X-linked dominant fashion

A

Alport’s syndrome
Rett syndrome
Vitamin D resistant rickets

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10
Q

Inheritance pattern of - Achondroplasia

A

autosomal dominant disorder

In most cases (approximately 70%) it occurs as a sporadic mutation

It is caused by a mutation in the fibroblast growth factor receptor 3 (FGFR-3) gene. This results in abnormal cartilage

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11
Q

Achondroplasia sx

A

short limbs (rhizomelia) with shortened fingers (brachydactyly)
large head with frontal bossing and narrow foramen magnum
midface hypoplasia with a flattened nasal bridge
‘trident’ hands
lumbar lordosis

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12
Q

Achondroplasia main risk factor

A

advancing parental age at the time of conception. Once present it is typically inherited in an autosomal dominant fashion.

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13
Q

Achondroplasia mx

A

There is no specific therapy.

some individuals benefit from limb lengthening procedures

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14
Q

Down’s syndrome features - face

A

upslanting palpebral fissures, epicanthic folds, Brushfield spots in iris, protruding tongue, small low-set ears, round/flat face
flat occiput

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15
Q

Down’s syndrome features - hands and feet

A

single palmar crease, pronounced ‘sandal gap’ between big and first toe

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16
Q

Down’s syndrome features hyper/hypotonia

A

hypotonia

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17
Q

Down’s syndrome features which cardiac complications?

A

congenital heart defects (40-50%)

multiple cardiac problems may be present
endocardial cushion defect
ventricular septal defect (c. 30%)
secundum atrial septal defect (c. 10%)
tetralogy of Fallot (c. 5%)
isolated patent ductus arteriosus
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18
Q

Down’s syndrome features which atresia

A

duodenal

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19
Q

Later complicactions of Down’s syndrome - describe fertility issues

A

males are almost always infertile due to impaired spermatogenesis. Females are usually subfertile, and have an increased incidence of problems with pregnancy and labour

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20
Q

Later complicactions of Down’s syndrome which infections?

A

repeated respiratory infections (+hearing impairment from glue ear)

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21
Q

Later complicactions of Down’s syndrome which dementia?

A

Alzheimer’s disease

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22
Q

Later complicactions of Down’s syndrome hyper/hypothyroidism

A

hypothyroidism

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23
Q

Later complicactions of Down’s syndrome causes atlantoaxial instability

A

true

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24
Q

Later complicactions of Down’s syndrome - which leukaemia?

A

acute lymphoblastic leukaemia

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25
Q

Duchenne muscular dystrophy is associated with which cardiac complication

A

dilated cardiomyopathy

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26
Q

Duchenne muscular dystrophy causes calf hypertrophy

A

false

calf pseudohypertrophy

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27
Q

Duchenne muscular dystrophy 30% of patients have intellectual impairment

A

true

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28
Q

Fragile X syndrome is a

A

trinucleotide repeat disorder.

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29
Q

Fragile X syndrome Features in males

- face

A

large low set ears, long thin face, high arched palate

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30
Q

Fragile X syndrome Features in males

micro/macro orchidism

A

macroorchidism

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31
Q

Fragile X syndrome Features in males

hyper/hypotonia

A

hypotonia

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32
Q

Fragile X syndrome - cardiac issues

A

mitral valve prolapse

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33
Q

Features in females (who have one fragile chromosome and one normal X chromosome) range from normal to mild

A

true

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34
Q

Fragile X syndrome diagnosis cannot be made antenatally

A

false

can be made antenatally by chorionic villus sampling or amniocentesis

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35
Q

Fragile X syndrome diagnosis based analysis of

A

number of CGG repeats using restriction endonuclease digestion and Southern blot analysis

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36
Q

Gene & Associated cancers

- p53

A

Common to many cancers, Li-Fraumeni syndrome

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37
Q

Gene & Associated cancers

- APC

A

Colorectal cancer

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38
Q

Gene & Associated cancers

- BRCA

A

Breast and ovarian cancer

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39
Q

Gene & Associated cancers

- NF1

A

Neurofibromatosis

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40
Q

Gene & Associated cancers

- Rb

A

Retinoblastoma

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41
Q

Gene & Associated cancers

- WT1

A

Wilm’s tumour

42
Q

Gene & Associated cancers

- Multiple tumor suppressor 1 (MTS-1, p16)

A

Melanoma

43
Q

Turner’s syndrome

is caused by?

A

resence of only one sex chromosome (X) or a deletion of the short arm of one of the X chromosomes. Turner’s syndrome is denoted as 45,XO or 45,X.

44
Q

Turner’s syndrome - cardiac complication?

A

bicuspid aortic valve (15%), coarctation of the aorta (5-10%)

45
Q

Turner’s syndrome - gonadotrophin levels will be elevated/low

A

elevated

46
Q

Turner’s syndrome causes lymphoedema in neonates (especially feet)

A

true

47
Q

Whilst most DNA is found in the cell nucleus, a small amount of double-stranded DNA is present in the mitochondria. It encodes

A

protein components of the respiratory chain and some special types of RNA

48
Q

Mitochondrial inheritance inheritance is only via

A

the maternal line as the sperm contributes no cytoplasm to the zygote

49
Q

Mitochondrial inheritance
none of the children of an affected male will inherit the disease
all of the children of an affected female will inherit the disease

A

true

50
Q

heteroplasmy is

A

poor genotype:phenotype correlation - within a tissue or cell there can be different mitochondrial populations

51
Q

Mitochondrial diseases histology?

A

muscle biopsy classically shows ‘red, ragged fibres’ due to increased number of mitochondria

52
Q

Mitochondrial diseases examples?

A 
Leber's optic atrophy
MELAS syndrome
MERRF syndrome
Kearns-Sayre syndrome
sensorineural hearing loss
53
Q

MELAS syndrome features?

A

mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes

54
Q

MERRF syndrome features?

A

myoclonus epilepsy with ragged-red fibres

55
Q

Kearns-Sayre syndrome features?

A

onset in patients < 20 years old, external ophthalmoplegia, retinitis pigmentosa. Ptosis may be seen

56
Q

Trinucleotide repeat disorders are

A

genetic conditions caused by an abnormal number of repeats (expansions) of a repetitive sequence of three nucleotides

57
Q

Trinucleotide repeat disorders are usually

A

neurological disorders

58
Q

Trinucleotide repeat disorders examples?

A 
Fragile X (CGG)
Huntington's (CAG)
myotonic dystrophy (CTG)
Friedreich's ataxia* (GAA)
spinocerebellar ataxia
spinobulbar muscular atrophy
dentatorubral pallidoluysian atrophy
59
Q

Trinucleotide repeat disorders may lead to an earlier age of onset in successive generations due to?

A

expansions are unstable and may enlarge

phenomenon known as anticipation

60
Q

Key features of Patau syndrome (trisomy 13)

A

Microcephalic, small eyes
Cleft lip/palate
Polydactyly
Scalp lesions

61
Q

Key features of Edward’s syndrome (trisomy 18)

A

Micrognathia
Low-set ears
Rocker bottom feet
Overlapping of fingers

62
Q

Key features of Fragile X

A 
Learning difficulties
Macrocephaly
Long face
Large ears
Macro-orchidism
63
Q

Key features of Noonan syndrome

A

Webbed neck
Pectus excavatum
Short stature
Pulmonary stenosis

64
Q

Key features of Pierre-Robin syndrome

A

Micrognathia
Posterior displacement of the tongue (may result in upper airway obstruction)
Cleft palate

65
Q

Key features of Prader-Willi syndrome

A

Hypotonia
Hypogonadism
Obesity

66
Q

Key features of William’s syndrome

A 
Short stature
Learning difficulties
Friendly, extrovert personality
Transient neonatal hypercalcaemia
Supravalvular aortic stenosis
67
Q

Key features of Cri du chat syndrome (chromosome 5p deletion syndrome)

A

Characteristic cry (hence the name) due to larynx and neurological problems
Feeding difficulties and poor weight gain
Learning difficulties
Microcephaly and micrognathism
Hypertelorism

68
Q

Prader-Willi syndrome is an example of genetic imprinting where the phenotype depends on whether the deletion occurs on a gene inherited from the mother or father:

A

Prader-Willi syndrome if gene deleted from father

Angelman syndrome if gene deleted from mother

69
Q

Prader-Willi syndrome is associated with the absence of the active Prader-Willi gene on the long arm of chromosome 15. This may be due to:

A

microdeletion of paternal 15q11-13 (70% of cases)

maternal uniparental disomy of chromosome 15

70
Q

Prader-Willi syndrome causes anorexia

A

false

childhood obesity

71
Q

McCune-Albright syndrome is not inherited

A

True

it is due to a random, somatic mutation in the GNAS gene.

72
Q

McCune-Albright syndrome - Features

A

precocious puberty
cafe-au-lait spots
polyostotic fibrous dysplasia
short stature

73
Q

What is Often thought of as the ‘male Turner’s’?

A

Noonan syndrome

74
Q

Noonan syndrome is thought to be caused by

A

a defect in a gene on chromosome 12

75
Q

Noonan syndrome characteristic clinical signs

A 
cardiac: pulmonary valve stenosis
ptosis
triangular-shaped face
low-set ears
coagulation problems: factor XI deficiency
76
Q

William’s syndrome is

A

inherited neurodevelopmental disorder caused by a microdeletion on chromosome 7

77
Q

William’s syndrome sx

A 
elfin-like facies
characteristic like affect - very friendly and social
learning difficulties
short stature
transient neonatal hypercalcaemia
supravalvular aortic stenosis
78
Q

William’s syndrome diagnosis

A

FISH studies

79
Q

Phenylketonuria (PKU) is

A

is an autosomal recessive condition caused by a disorder of phenylalanine metabolism. This is usually due to defect in phenylalanine hydroxylase, an enzyme which converts phenylalanine to tyrosine

80
Q

High levels of phenylalanine lead to problems such as

A

learning difficulties and seizures

81
Q

Phenylketonuria sx

A

usually presents by 6 months e.g. with developmental delay
child classically has fair hair and blue eyes
learning difficulties
seizures, typically infantile spasms
eczema
‘musty’ odour to urine and sweat*

82
Q

Phenylketonuria diagnosis

A

Guthrie test: the ‘heel-prick’ test done at 5-9 days of life - also looks for other biochemical disorders such as hypothyroidism
hyperphenylalaninaemia
phenylpyruvic acid in urine

83
Q

Phenylketonuria mx

A

dietary restrictions are however important during pregnancy as genetically normal fetuses may be affected by high maternal phenylalanine levels

84
Q

hypochromic and microcytic, but the Hb level would be typically normal suggests which alpha thalassemia?

A

1 or 2 alpha globulin alleles are affected

85
Q

hypochromic microcytic anaemia with splenomegaly suggests which alpha thalassemia?

A

Hb H disease

3 alpha globulin alleles are affected

86
Q

death in utero (hydrops fetalis, Bart’s hydrops) suggests which alpha thalassemia?

A

4 alpha globulin alleles are affected (i.e. homozygote)

87
Q

High LH
Low Testosterone
- Which disorder of sex hormones?

A

Primary hypogonadism (Klinefelter’s syndrome)

88
Q

Low LH
Low Testosterone
- Which disorder of sex hormones?

A

Hypogonadotrophic hypogonadism (Kallman’s syndrome)

89
Q

High LH
Normal/high Testosterone
- Which disorder of sex hormones?

A

Androgen insensitivity syndrome

90
Q

Low LH
High Testosterone
- Which disorder of sex hormones?

A

Testosterone-secreting tumour

91
Q

Klinefelter’s syndrome is associated with karyotype

A

47, XXY

92
Q

Klinefelter’s syndrome features?

A 
often taller than average
lack of secondary sexual characteristics
small, firm testes
infertile
gynaecomastia - increased incidence of breast cancer
93
Q

Kallman’s syndrome is a recognised cause of delayed puberty secondary to hypogonadotrophic hypogonadism. It is usually inherited as

A

X-linked recessive trait

94
Q

Kallman’s syndrome is thought to be caused by

A

failure of GnRH-secreting neurons to migrate to the hypothalamus.

95
Q

Androgen insensitivity syndrome is an

A

X-linked recessive condition due to end-organ resistance to testosterone causing genotypically male children (46XY) to have a female phenotype

96
Q

Androgen insensitivity syndrome

features

A

‘primary amenorrhoea’
undescended testes causing groin swellings
breast development may occur as a result of conversion of testosterone to oestradiol

97
Q

Androgen insensitivity syndrome diagnosis

A

buccal smear or chromosomal analysis to reveal 46XY genotype

98
Q

Androgen insensitivity syndrome management

A 
counselling - raise child as female
bilateral orchidectomy (increased risk of testicular cancer due to undescended testes)
oestrogen therapy
99
Q

Homocystinuria is

A

a rare autosomal recessive disease caused by a deficiency of cystathionine beta synthase. This results in severe elevations in plasma and urine homocysteine concentrations.

100
Q

Homocystinuria Features

A

often patients have fine, fair hair
musculoskeletal
Marfanoid body habitus: arachnodactyly etc
osteoporosis
kyphosis
neurological: may have learning difficulties, seizures
ocular
downwards (inferonasal) dislocation of lens
severe myopia
increased risk of arterial and venous thromboembolism
also malar flush, livedo reticularis

101
Q

Homocystinuria ix

A

increased homocysteine levels in serum and urine

cyanide-nitroprusside test: also positive in cystinuria

102
Q

Homocystinuria mx

A

Treatment is vitamin B6 (pyridoxine) supplements.

4th year passmedicine by topic (96 decks)

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