Genetics - Genetic Disorders Flashcards by amo x

What is Down’s syndrome?

It is a genetic disorder caused by the presence a copy of chromosome 21 (trisomy 21)

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What are the three main mechanisms of Down’s syndrome?

Maternal nondisjunction

Robertsonian translation

Mocaicism

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What is the most common mechanism of Down’s syndrome?

Maternal nondisjunction

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What are the eight clinical features of Down’s syndrome?

Facial abnormalities

Flat occiput

Single palmar crease

Pronounced sandal gap

Hypotonia

Congenital heart defects

Duodenal artersia

Hirschprung’s disease

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What six facial abnormalities are associated with Down’s?

Upslanting palpebral fissures

Epicanthic folds

Brushfield spots in iris

Protruding tongue

Small low-set ears

Round/flat face

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What five cardiac abnormalities are associated with Down’s syndrome?

Endocardial cushion defect

Ventricular septal defect

Secundum atrial septal defect

Tetralogy of Fallot

Isolated patent ductus arteriosus

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What is the most common cardiac abnormalities in Down’s syndrome?

Endocardial cushion defect

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What are the eight later complications of Down’s syndrome?

Subfertility

Learning difficulties

Short stature

Respiratory infections

ALL

Hypothyroidism

Alzheimer’s disease

Atlantoaxial instability

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What is the first line investigation used to screen for Down’s syndrome?

Combined test

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What is the combined test?

Nuchal translucency measurement

Serum B-hCG levels

Pregnancy associated plasma protein A (PAPP-A)

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When is the combined test conducted?

11 - 13+6 weeks

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What combined test result indicates Down’s syndrome?

Thickened nuchal translucency

Increased b-hCG

Decreased PAPPA

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What two other tests are used to screen for Down’s syndrome between 15-20 weeks?

Triple test

Quadruple test

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What is the triple test?

Alpha-fetoprotein

Unconjugated estriol

b-hCG

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What is the quadruple test?

Alpha-fetoprotein

Unconjugated estriol

b-hCG

Inhibin A

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What is Patau’s syndrome?

It is a genetic disorder caused by the presence a copy of chromosome 13 (trisomy 13)

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What are the five clinical features of Patau syndrome?

Microcephalic

Small eyes

Cleft lip/palate

Polydactyly

Scalp lesions

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What is Edward’s syndrome?

It is a genetic disorder caused by the presence a copy of chromosome 18 (trisomy 18)

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What are the four clinical features of Edward’s syndrome?

Micrognathia

Low-set ears

Rocker bottom feet

Overlapping of fingers

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What is Turner’s syndrome?

It is caused by either the presence of only one sex chromosome (X) or a deletion of the short arm of one of the X chromosomes

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What phenotype denotes Turner’s syndrome?

45,XO

45,X

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What is the most common mechanism of Turner’s syndrome?

Mosaicism

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What is mosaicism?

It is defined as the presence of two genetically different populations of cells in the body

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What are the twelve clinical features of Turner’s syndrome?

Short stature

Widely spaced nipples

Webbed neck

Cardiac abnormalities

Primary amenorrhoea

Cystic hygroma

High arched palate

Short forth metacarpal

Multiple pigmented naevei

Lymphoedmea

Hypothyroidism

Renal abnormalities

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What two cardiac abnormalities are associated with Turner's syndrome?

Bicuspid aortic valve Coarctation of the aorta

What renal abnormality is associated with Turner's syndrome?

Horshoe kidney

What is Klinfelter's syndrome?

It is a genetic condition that results when a boy is born with an extra copy of the X chromosome

What phenotype denotes Klinfelter's syndrome?

47, XXY

What are the five clinical features associated with Klinfelter's syndrome?

Tall Lack of secondary sexual characteristics Small, firm testes Infertile Gynaecomastia

What genetic test is used to diagnose Klinefelter's syndrome?

Karyotype

What blood test is used to indicate Klinefelter's syndrome?

Increased gonadotropin levels Low testosterone levels

What is Noonan's syndrome?

It is a genetic condition associated with a PTPN11 mutation on chromosome 12

What inheritance is demonstrated in Noonan's syndrome?

Autosomal dominant

What are the four clinical features of Noonan's syndrome?

Webbed neck Pectus excavatum Short stature Pulmonary stenosis

What is William's syndrome?

It is an inherited neurodevelopmental disorder caused by a microdeletion on chromosome 7

What are the six clinical features of William's syndrome?

Ellfin-like facies Friendly character Learning difficulties Short stature Transient neonatal hypercalcaemia Supravalvular aortic stenosis

How do we diagnose William's syndrome?

FISH study

What is DiGeorge syndrome?

It is a primary T-cell immunodeficiency disorder

What is the cause of DiGeorge syndrome?

A deletion of a section of chromosome 22

What are two other names for DiGeorge syndrome?

Velocardiofacial syndrome 22q11.2 deletion syndrome

What is the inheritance of DiGeorge syndrome?

Autosomal dominant

What are the six clinical features of DiGeorge syndrome?

CATCH Cardiac abnormalities Abnormal facies Thymic aplasia Cleft palate Hypocalcaemia/ hypoparathyroidism

What is Marfan's syndrome?

It is a genetic connective tissue disorder It is caused by a defect in the FBN1 gene on chromosome 15 that codes for the protein fibrillin-1

What inheritance is demonstrated in Marfan's syndrome?

Autosomal dominant

What are the ten clinical features of Marfan's syndrome?

Tall stature High-arched palate Arachnodactyly Pectus excavatum Pes planus Scoliosis Cardiac abnormalities Pneumothoraces Eye abnormalities Dural ectasia

What four cardiac abnormalities are associated with Marfan's syndrome?

Dilation of the aortic sinuses Aortic dissection Aortic regurgitation Mitral valve prolapse

What are the three eye abnormalities associated with Marfan's syndrome?

Upwards lens dislocation Blue sclera Myopia

What is dural ectasia?

It is ballooning of the dural sac at the lumbosacral level

What scan do we conduct annually in Marfan's syndrome patients?

ECHO scan

What two drugs are used to manage Marfan's syndrome?

Beta-blockers ARBs

What is phenylketonuria (PKU)?

It is a genetic condition caused by a disorder of phenylalanine metabolism This is usually due to defect in phenylalanine hydroxylase, an enzyme which converts phenylalanine to tyrosine This leads to an accumulation of phenylalanine

What type of inheritance is PKU?

Autosomal recessive

On what chromosome is phenylalanine hydroxylase located on?

When does PKU tend to present?

6 months

What are the five clinical features of PKU?

Developmental delay Seizures Learning disabilities Eczema Musty odour to urine and sweat

What test is used to diagnose PKU?

Guthrie test, also known as the heel prick test

When is the Guthrie test conducted?

5-9 days after birth

What blood result indicates PKU?

Hyperphenylalaninaemia

What urine result indicates PKU?

Phenylpyruvic acid

How do we manage PKU?

We advise dietary restrictions during pregnancy and after birth

What is pleiotropy? Name an example

It refers to a mutation in a single gene causing pathology in multiple organ systems PKU

What is Prader Willi syndrome?

It is a genetic condition associated with the absence of the active Prader-Willi gene on the long arm of chromosome 15

What are the two pathophysiological causes of Prader Willi syndrome?

Microdeletion of paternal 15q11-13 Maternal uniparental disomy of chromosome 15

Prader Willi syndrome is an example of genetic imprinting. What does this mean?

It is defined as a difference in phenotype dependent on whether the mutation is maternal or paternal origin

What syndrome results in cases where the deletion of the Prader Willi gene is from the mother?

Angelman syndrome

What are the six clinical features of Prader Willi syndrome?

Hypotonia Short stature Hypogonadism Learning difficulties Childhood obesity Behavioural problems

What is long QT syndrome?

It is an inherited condition associated with delayed repolarisation of the ventricles

What is the normal QT interval in males?

< 430ms

What is the normal QT interval in females?

< 450ms

What is the cause of long QT syndrome?

It caused by defects in the alpha subunit of the slow delayed rectifier potassium channel

What are the two congenital syndromes that cause long QT syndrome?

Romano-Ward syndrome Jervell-Lange-Nielsen syndrome

What are the three classifications of long QT syndrome?

Long QT1 Long QT2 Long QT3

What is long QT1?

It is usually associated with exertional syncope, often swimming

What is long QT2?

It is usually associated with syncope occurring following emotional stress, exercise or auditory stimuli

What is long QT3?

It is usually associated with syncope at night or at rest

What scan is used to diagnose long QT syndrome?

ECG

What are the three features of long QT syndrome on an ECG scan?

Prolonged QT interval Repolarisation anomalies Paroxysmal polymorphic VT

How do we manage long QT syndrome?

Beta blockers

What are the two complications of long QT syndrome?

Ventricular tachycardia Torsade de pointes

What is neurofibromatosis?

It is a genetic condition that that results in tumour growth along nerves

What is the inheritance of neurofibromatosis?

Autosomal dominant

What are the two classification of neurofibromatosis?

NF 1 NF 2

What is another term for NF1?

von Recklinghausen's syndrome

What is the cause of NF1?

It is caused by a gene mutation on chromosome 17 which encodes neurofibromin

What are the six clinical features of NF1?

Café-au-lait spots Axillary/groin freckles Peripheral neurofibromas Iris hamatomas Scoliosis Pheochromocytomas

What is the cause of NF2?

It is caused by gene mutation on chromosome 22

What are the four clinical features of NF2?

Bilateral vestibular schwannomas Multiple intracranial schwannomas Multiple intracranial mengiomas Multiple intracranial ependymomas

What is tuberous sclerosis (TS)?

It is a genetic condition that causes benign tumours to develop in various areas of the body

What is the inheritance of tuberous sclerosis?

Autosomal dominant

What are the five cutaneous clinical features of tuberous sclerosis?

Depigmented 'ash-leaf' spots which fluoresce under UV light Roughened patches of skin over lumbar spine Angiofibromas Subungual fibromata Cafe-au-lait spots

What are the three neurological clinical features of tuberous sclerosis?

Developmental delay Epilepsy Intellectual impairment

Genetics - Genetic Disorders Flashcards

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