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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
What are the other symptoms of Tay-Sachs disease?
After 3 months - hypotonia, myoclonic jerks, LD and regression, seizures, dementia
26
What is the cause of Gaucher disease?
Autosomal recessive | b-glucocerebrosidase accumulates in brain, liver, spleen
27
What are the features of Gaucher disease?
``` Hepatosplenomegaly Anaemia Osteopenia Type 1: less severe, no neuro symptoms, may be incidental Types 2 and 3 present in infancy ```
28
Which glycogen storage disorder is caused by deficiency of glycogen phosphorylase?
McArdle's disease type V | Hypotonia from skeletal muscle glycogen accumulation
29
What type of immunodeficiency is present in Di-George syndrome?
T cell
30
What is the inheritance of Di-George syndrome?
Autosomal dominant | 22q11.2 deletion
31
What are the features of Di-George syndrome?
CATCH-22 ``` Cardiac abnormalities Abnormal facies Thymic aplasia Cleft palate Hypocalcaemia/hypoparathyroid ```
32
What type of infections are patients with Di-George syndrome at risk of?
Viral and fungal infections
33
Mutation in the WASP gene causes what syndrome?
Wiskott-Aldrich | X-linked recessive
34
What are the features of Wiskott-Aldrich syndrome?
Recurrent bacterial infection - combined B and T cell dysfunction Eczema Thrombocytopenia
35
Which antibody is low in Wiskott-Aldrich syndrome?
IgM
36
What is the name of the condition which results in juvenile gout, learning difficulties, and aggression?
Lesch-Nyhan syndrome
37
What is the inheritance of Lesch-Nyhan syndrome?
X-linked recessive
38
Why does uric acid accumulate in Lesch-Nyhan syndrome?
Defect in purine synthesis salvage pathway and absence of HGPRT enzyme
39
What is the karyotype of Turner's syndrome?
45XO | Only 1 sex chromosome, or deletion of short arms of 1 X chromosome
40
What are the features of Turner's syndrome?
``` Short stature Shield chest Webbed neck Primary amenorrhoea Hypothyroidism High arched palate Horseshoe kidney ```
41
What are the cardiac abnormalities in Turner's syndrome and the prevalence?
Bicuspid aortic valve - 15% | Coarctation of the aorta - 10%
42
Are gonadotrophin levels low or high in Turner's syndrome?
High
43
Which autosomal dominant condition with a defect on chromosome 12, results in factor XI deficiency?
Noonan syndrome
44
What are the other features of Noonan syndrome?
``` Short stature Webbed neck Pectus carinatum/excavatum Pulmonary stenosis Ptosis Triangle face Low set ears ```
45
What is the genetics of Prader-Willi syndrome?
Genetic imprinting | Paternal 15q11-12 in 70%
46
What are the features of Prader-Willi syndrome?
``` Hypotonia Dysmorphic face Short stature Hypogonadism LD Obesity ```
47
A mutation in the fibroblast growth factor receptor (FGFR3) gene causes what condition?
Achondroplasia | Autosomal dominant
48
What is a risk factor for achondroplasia?
Advancing parental age
49
What is the trinucleotide repeat in Fragile X syndrome?
CGG
50
What are the features of Fragile X syndrome?
``` LD Large low set ears Long thin face High arched palate Macro-orchidism Hypotonia MV prolapse ```
51
What is the cause of Alport syndrome?
X-linked dominant | Defective T4 collagen = defective glomerular basement membrane
52
What are the features of Alport syndrome?
Microscopic haematuria --> end stage renal failure Bilateral sensorineural deafness Lenticonus and retinitis pigmentosa
53
What is seen electron microscopy of renal biopsy in Alport syndrome?
Splitting of lamina densa of GBM - basket weave
54
In which gender is Alport syndrome more severe?
Males
55
What is the inheritance and cause of Kallmann's syndrome?
X-linked recessive | Failure of GnRH secreting neurons to migrate to the hypothalamus
56
What are the features of Kallmann's syndrome?
``` Anosmia Delayed puberty and hypogonadism Tall stature cryptorchidism Visual/hearing defects ```
57
How is Kallmann's syndrome diagnosed?
Low sex hormones | LH and FSH low/normal
58
What is the karyotype of Klinefelter's syndrome?
47XXY
59
What are the features of Klinefelter's syndrome?
``` Tall stature Small firm testes Gynaecomastia Lack of secondary sexual characteristics Infertile ```
60
How is Klinefelter's syndrome diagnosed?
Elevated gonadotrophins | Low testosterone
61
Which AR syndrome results from defect of sodium-chloride cotransporter in the distal convuluted tubule?
Gitelman's syndrome
62
What are the features of Gitelman's syndrome?
``` Low K Low Mg Low Ca in urine Alkaline urine Normotension ```
63
Which AR syndrome results from defect in Na-K-Cl co-transporter of LoH?
Bartter's syndrome
64
What are the features of Bartter's syndrome?
Low K Normotension Weakness Polyuria
65
What is the cause and features of Liddle's syndrome?
Defect in epithelial sodium channels in DCT Low K Hypertension
66
What tumours are seen in von-hippel-lindau syndrome?
Cerebellar haemangiomas Retinal haemangiomas ---> vitreous haemorrhage Phaeochromocytoma Renal/liver/pancreatic cysts
67
Where is the VHL gene located?
Chromosome 3
68
What is the condition characterised by pigmented freckles on lips, face, palms, and soles, and GI bleeds?
Peutz-Jegher's syndrome
69
What is the cause of Peutz-Jegher's syndrome?
Autosomal dominant | Serine threonine kinase LKB-1 or STK-11
70
50% of people with Peutz-Jegher's syndrome die from what?
GI tract cancer
71
What is the cause of Friedreich's ataxia?
Autosomal recessive | Chromosome 9 GAA triplet repeat which codes for frataxin
72
What are the features of FA?
``` Mixed UMN/LMN/cerebellar signs Pes cavus Optic atrophy Diabetes HCOM ```
73
What are the features of the AR condition ataxia telangiectasia?
Cerebellar ataxia Telangiectasia IgA deficiency Increased risk of leukaemia/lymphoma
74
When do FA and AT present?
FA: 10-15 years AT: 1-5 years
75
What is the cause of Gilbert's syndrome?
Deficiency of UDP-glucuronosyltransferase --> defective conjugation of bilirubin
76
What type of bilirubin is seen in Gilbert's syndrome?
Unconjugated No bilirubin in urine
77
What is Dubin-Johnson syndrome?
Defective hepatic bilirubin excretion due to defect in canallicular multispecific organic anion transporter
78
What are the features of Dubin-Johnson syndrome?
Presents in teenage years with jaundice Conjugated hyperbilirubinaemia Bilirubin in urine Black liver
79
Which protein holds DNA together to form chromosomes?
Histone
80
What is the structure of DNA?
Nitrogenous base - adenine, cytosine, guanine, thymine | Sugar-phosphate backbone
81
DNA replication is achieved by splitting DNA into what, and how?
Leading and lagging strands | By DNA helicase
82
In which conditions is anticipation seen?
Huntington's Fragile X syndrome Myotonic dystrophy
83
What are the features of Leber's optic atrophy?
Subacute loss of binocular vision Improper colour vision Lesion of central vision Optic nerve atrophy
84
How is myotonic dystrophy diagnosed?
Genetic testing - expanded CTG repeat in DMPK gene | >50 repeats = confirmatory
85
What is a rare cause of adrenal insufficiency that can be mistaken for multiple sclerosis?
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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