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MRCP > Genetics > Flashcards

Genetics Flashcards

1
Q

What are the features of MELAS syndrome?

A

Myopathy, encephalopathy, lactic acidosis, and stroke like episodes

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2
Q

What type of inheritance is MELAS syndrome and Kearns-Sayre syndrome?

A

Mitochondrial

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3
Q

What are the features of Kearns-Sayer syndrome?

A

Ptosis and external ophthalmoplegia
Retinitis pigmentosa
Proximal myopathy
AV nodal block

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4
Q

How is MELAS syndrome diagnosed?

A

Multifocal hyperintense cortical lesions
Increased lactate in serum and CSF
Biopsy - ragged red fibres

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5
Q

When should you suspect MELAS syndrome?

A

Young people with atypical stroke like episodes that cross vascular territories

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6
Q

How is Kearns-Sayer syndrome diagnosed

A

Ragged red fibres

Elevated serum lactate and pyruvate

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7
Q

What is the cause of homocystinuria?

A

Autosomal recessive

Deficiency of cystathione beta synthase

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8
Q

What are the features of homocystinuria?

A 
Marfinoid body habitus
LD
Kyphosis
Downwards dislocation of lens and myopia
Increased risk of VTE
Malar flush and livedo reticularis
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9
Q

How is homocystinuria diagnosed?

A

Increased homocysteine in serum and urine

Cyanide nitroprusside test

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10
Q

What is the treatment of homocystinuria?

A

Vitamin B6 pyridoxine

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11
Q

What is the cause of cystinuria?

A

Autosomal recessive
Chromosome 2: SLC3A1 gene or chromosome 19: SLC7A9 gene

Defect in membrane transport of cystine, ornithine, lysine, arginine –> inadequate reabsorption in PCT

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12
Q

What is the main feature of cystinuria?

A

Yellow and crystalline nephrocalcinosis

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13
Q

What is the treatment of cystinuria?

A

Hydration
D-penicillamine
Urinary alkalinisation

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14
Q

How is cystinuria diagnosed?

A

Cyanide nitroprusside test

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15
Q

What is the cause of phenylketonuria?

A

Autosomal recessive

Chromosome 12 - phenylalanine hydroxylase defect

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16
Q

What are the features of phenylketonuria and when does it present?

A 
LD
Infantile spasms
Eczema
Fair hair and blue eyes
Musty odour to urine and sweat

Presents by 6 months

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17
Q

How is PKU diagnosed?

A

Guthrie test
Hyperphenylalaninaemia
Phenylpyruvic acid in urine

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18
Q

What is the inheritance of Fabry disease?

A

X-linked recessive

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19
Q

What is the pathophysiology of Fabry disease

A

Deficiency of galactosidase A –> accumulation of glycosphingolipids (ceramide trihexoside) in lysosomes

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20
Q

What are the features of Fabry disease?

A 
Acute neuropathic/limb pain episodes with stress, hot, cold
Angiokeratomas
Corneal whirls
Hypohidrosis
CV complications
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21
Q

What is the most common lysosomal storage disorder?

A

Gaucher disease

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22
Q

What is the treatment of Fabry disease?

A

Agalsidase alpha replacement

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23
Q

In which 2 lysosomal storage disorders is a cherry red spot seen on the macula?

A

Tay-Sachs disease

Niemann-Pick disease

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24
Q

What is the difference between Tay-Sachs disease and Niemann Pick disease?

A

TS: defect in hexosaminidase A, normal liver and spleen size
NP: defect in sphingomyelinase, hepatosplenomegaly

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25
Q

What are the other symptoms of Tay-Sachs disease?

A

After 3 months - hypotonia, myoclonic jerks, LD and regression, seizures, dementia

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26
Q

What is the cause of Gaucher disease?

A

Autosomal recessive

b-glucocerebrosidase accumulates in brain, liver, spleen

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27
Q

What are the features of Gaucher disease?

A 
Hepatosplenomegaly
Anaemia
Osteopenia
Type 1: less severe, no neuro symptoms, may be incidental
Types 2 and 3 present in infancy
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28
Q

Which glycogen storage disorder is caused by deficiency of glycogen phosphorylase?

A

McArdle’s disease type V

Hypotonia from skeletal muscle glycogen accumulation

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29
Q

What type of immunodeficiency is present in Di-George syndrome?

A

T cell

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30
Q

What is the inheritance of Di-George syndrome?

A

Autosomal dominant

22q11.2 deletion

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31
Q

What are the features of Di-George syndrome?

A

CATCH-22

Cardiac abnormalities
Abnormal facies
Thymic aplasia
Cleft palate
Hypocalcaemia/hypoparathyroid
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32
Q

What type of infections are patients with Di-George syndrome at risk of?

A

Viral and fungal infections

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33
Q

Mutation in the WASP gene causes what syndrome?

A

Wiskott-Aldrich

X-linked recessive

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34
Q

What are the features of Wiskott-Aldrich syndrome?

A

Recurrent bacterial infection - combined B and T cell dysfunction
Eczema
Thrombocytopenia

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35
Q

Which antibody is low in Wiskott-Aldrich syndrome?

A

IgM

36
Q

What is the name of the condition which results in juvenile gout, learning difficulties, and aggression?

A

Lesch-Nyhan syndrome

37
Q

What is the inheritance of Lesch-Nyhan syndrome?

A

X-linked recessive

38
Q

Why does uric acid accumulate in Lesch-Nyhan syndrome?

A

Defect in purine synthesis salvage pathway and absence of HGPRT enzyme

39
Q

What is the karyotype of Turner’s syndrome?

A

45XO

Only 1 sex chromosome, or deletion of short arms of 1 X chromosome

40
Q

What are the features of Turner’s syndrome?

A 
Short stature
Shield chest
Webbed neck
Primary amenorrhoea
Hypothyroidism
High arched palate
Horseshoe kidney
41
Q

What are the cardiac abnormalities in Turner’s syndrome and the prevalence?

A

Bicuspid aortic valve - 15%

Coarctation of the aorta - 10%

42
Q

Are gonadotrophin levels low or high in Turner’s syndrome?

A

High

43
Q

Which autosomal dominant condition with a defect on chromosome 12, results in factor XI deficiency?

A

Noonan syndrome

44
Q

What are the other features of Noonan syndrome?

A 
Short stature
Webbed neck
Pectus carinatum/excavatum
Pulmonary stenosis
Ptosis
Triangle face
Low set ears
45
Q

What is the genetics of Prader-Willi syndrome?

A

Genetic imprinting

Paternal 15q11-12 in 70%

46
Q

What are the features of Prader-Willi syndrome?

A 
Hypotonia
Dysmorphic face
Short stature
Hypogonadism
LD
Obesity
47
Q

A mutation in the fibroblast growth factor receptor (FGFR3) gene causes what condition?

A

Achondroplasia

Autosomal dominant

48
Q

What is a risk factor for achondroplasia?

A

Advancing parental age

49
Q

What is the trinucleotide repeat in Fragile X syndrome?

A

CGG

50
Q

What are the features of Fragile X syndrome?

A 
LD
Large low set ears
Long thin face
High arched palate
Macro-orchidism
Hypotonia
MV prolapse
51
Q

What is the cause of Alport syndrome?

A

X-linked dominant

Defective T4 collagen = defective glomerular basement membrane

52
Q

What are the features of Alport syndrome?

A

Microscopic haematuria –> end stage renal failure
Bilateral sensorineural deafness
Lenticonus and retinitis pigmentosa

53
Q

What is seen electron microscopy of renal biopsy in Alport syndrome?

A

Splitting of lamina densa of GBM - basket weave

54
Q

In which gender is Alport syndrome more severe?

A

Males

55
Q

What is the inheritance and cause of Kallmann’s syndrome?

A

X-linked recessive

Failure of GnRH secreting neurons to migrate to the hypothalamus

56
Q

What are the features of Kallmann’s syndrome?

A 
Anosmia
Delayed puberty and hypogonadism
Tall stature
cryptorchidism
Visual/hearing defects
57
Q

How is Kallmann’s syndrome diagnosed?

A

Low sex hormones

LH and FSH low/normal

58
Q

What is the karyotype of Klinefelter’s syndrome?

A

47XXY

59
Q

What are the features of Klinefelter’s syndrome?

A 
Tall stature
Small firm testes
Gynaecomastia
Lack of secondary sexual characteristics
Infertile
60
Q

How is Klinefelter’s syndrome diagnosed?

A

Elevated gonadotrophins

Low testosterone

61
Q

Which AR syndrome results from defect of sodium-chloride cotransporter in the distal convuluted tubule?

A

Gitelman’s syndrome

62
Q

What are the features of Gitelman’s syndrome?

A 
Low K
Low Mg
Low Ca in urine
Alkaline urine
Normotension
63
Q

Which AR syndrome results from defect in Na-K-Cl co-transporter of LoH?

A

Bartter’s syndrome

64
Q

What are the features of Bartter’s syndrome?

A

Low K
Normotension
Weakness
Polyuria

65
Q

What is the cause and features of Liddle’s syndrome?

A

Defect in epithelial sodium channels in DCT
Low K
Hypertension

66
Q

What tumours are seen in von-hippel-lindau syndrome?

A

Cerebellar haemangiomas
Retinal haemangiomas —> vitreous haemorrhage
Phaeochromocytoma
Renal/liver/pancreatic cysts

67
Q

Where is the VHL gene located?

A

Chromosome 3

68
Q

What is the condition characterised by pigmented freckles on lips, face, palms, and soles, and GI bleeds?

A

Peutz-Jegher’s syndrome

69
Q

What is the cause of Peutz-Jegher’s syndrome?

A

Autosomal dominant

Serine threonine kinase LKB-1 or STK-11

70
Q

50% of people with Peutz-Jegher’s syndrome die from what?

A

GI tract cancer

71
Q

What is the cause of Friedreich’s ataxia?

A

Autosomal recessive

Chromosome 9 GAA triplet repeat which codes for frataxin

72
Q

What are the features of FA?

A 
Mixed UMN/LMN/cerebellar signs
Pes cavus
Optic atrophy
Diabetes
HCOM
73
Q

What are the features of the AR condition ataxia telangiectasia?

A

Cerebellar ataxia
Telangiectasia
IgA deficiency
Increased risk of leukaemia/lymphoma

74
Q

When do FA and AT present?

A

FA: 10-15 years
AT: 1-5 years

75
Q

What is the cause of Gilbert’s syndrome?

A

Deficiency of UDP-glucuronosyltransferase –> defective conjugation of bilirubin

76
Q

What type of bilirubin is seen in Gilbert’s syndrome?

A

Unconjugated

No bilirubin in urine

77
Q

What is Dubin-Johnson syndrome?

A

Defective hepatic bilirubin excretion due to defect in canallicular multispecific organic anion transporter

78
Q

What are the features of Dubin-Johnson syndrome?

A

Presents in teenage years with jaundice
Conjugated hyperbilirubinaemia
Bilirubin in urine
Black liver

79
Q

Which protein holds DNA together to form chromosomes?

A

Histone

80
Q

What is the structure of DNA?

A

Nitrogenous base - adenine, cytosine, guanine, thymine

Sugar-phosphate backbone

81
Q

DNA replication is achieved by splitting DNA into what, and how?

A

Leading and lagging strands

By DNA helicase

82
Q

In which conditions is anticipation seen?

A

Huntington’s
Fragile X syndrome
Myotonic dystrophy

83
Q

What are the features of Leber’s optic atrophy?

A

Subacute loss of binocular vision
Improper colour vision
Lesion of central vision
Optic nerve atrophy

84
Q

How is myotonic dystrophy diagnosed?

A

Genetic testing - expanded CTG repeat in DMPK gene

>50 repeats = confirmatory

85
Q

What is a rare cause of adrenal insufficiency that can be mistaken for multiple sclerosis?

A

X-linked adrenoleukodystrophy
Mutation in ABCD1 gene - codes for ALD which is a peroxisomal membrane transporter protein
Peripheral neuropathy/myelopathy with adrenal failure

MRCP (17 decks)

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