Common Genetic Conditions (FRAX, T18, T13) Excludes DS

Question 1

What is Edwards Syndrome?

Answer 1

T18

Question 2

What is the female: male prevalence of T18?

Answer 2

3F:1M

Question 3

Head / brain features of T18?

Answer 3

• Microcephaly

- Prominent occiput

Question 4

Eyes features of T18?

Answer 4

• Microopthalmia
• Hypertelorism
• Iris coloboma
• Retinal anomalies

Question 5

Prognosis T18?

Answer 5

44% die in first month; 10% survive past 1y

Question 6

What are the characteristic features of Edwards syndrome?

Answer 6

• Multi organ defects
• Small, abnormally shaped head
• Small jaw and mouth
• Clenched fists with overlapping fingers

Question 7

What is the appearance phenotype of FRAX?

Answer 7

Overgrowth:

• Prominent jaw, forehead, nasal bridge
• Long, narrow face
• Large ears
• Joint hyper mobility
• Testicular enlargement in adolescents
• High arched palate

Question 8

What are the implications of FRAX for development?

Answer 8

• Moderate mental retardation
• Reduced coordination
• Risk of epilepsy

Question 9

Behavioural features of FRAX?

Answer 9

• ADHD
• Social shyness
• ASD features

Question 10

What is the genotype of FRAX?

Answer 10

CCG triplet repeat on X chromosome

• X linked
• Demonstrates anticipation

Question 11

What is the most common heritable cause of ID in boys?

Answer 11

FRAX

Question 12

What are the complications of FRAX phenotype?

Answer 12

• Seizures
• Scoliosis
• Mitral valve prolapse

Question 13

How is FRAX diagnosed?

Answer 13

Molecular testing of FMR1 gene: overamplification of trinucleotide repeat; length of segment proportional to severity of clinical phenotype

Question 14

What are neurocutaneous syndromes?

Answer 14

Broad term for group of neurologic (brain, spine and nerve) disorders. Cause tumours to grow in brain, spinal cord, organs, skin and skeletal bones.

Question 15

What are the three most common types of neurocutaneous syndromes?

Answer 15

• Tuberous sclerosis
• Neurofibromatosis
• Sturge Weber disease

Question 16

What is inheritance pattern of Tuberous Sclerosis?

Answer 16

Autosomal Dominant BUT 50% new mutations

Question 17

What are the cutaneous features of TS?

Answer 17

• Adenoma sebaceum (angiokeratomas on face, often malar distribution)
• Shagreen patch (isolated raised plaque over lower back, buttocks)
• “ash leaf” hypo pigmentation seen with Wood’s lamp

Question 18

What are the features of Sturge Weber syndrome?

Answer 18

• port wine stain in V1 distribution
• associated angiomatous malformations of the brain causing contralateral hemiparesis and hemiatrophy
• A/w seizure, glaucoma and mental retardation

Question 19

What is NFII characterised by?

Answer 19

Predisposition to intracranial and spinal tumours. Diagnosed when either bilateral vestibular schwannomas found OR first degree relative with NF2 and presence of neurofiborma, meningioma, glioma or schwanomma.

Question 20

What are the features of NFI?

Answer 20

- Learning disorders, seizures, slow speech common
Diagnosis requires:
- Cafe au last spots
- Neurofibromas
- Lisch nodules (hamartomas of the iris)
-optic glioma
- freckling in axillary or inguinal region
- first degree relative with NF1