Chromosome 15 disorders

Question 1

Prader-Willi Syndrome results when genetic information is missing from the______.

Answer 1

paternal allele of 15q11-q13

Question 2

3 ways to get PWD:

Answer 2

1. Deletion on paternal 2. Uniparental disomy 3. imprinting error

Question 3

Testing?

Answer 3

Methylation test, then FISH or CMA to verify deletion.

Question 4

Infant presenting with PWS may have?

Answer 4

Hypotonia, feeding issues (won’t cry to feed, can’t suck, often need G-tube), undescended testicles if male, hypopigmentation (pale and blonde)

Question 5

Opthalmic concerns of PWS?

Answer 5

Nystagmus, strabismus

Question 6

Orthopedic concerns of PWS?

Answer 6

Scoliosis

Question 7

Respiratory concerns of PWS?

Answer 7

Obstructive sleep apnea. (contraindication to use of Growth Hormone)

Question 8

Developmental concerns of PWS?

Answer 8

Late to walk, (3 years?), mild-moderate cognitive impairment, behavioral issues, hyperphagia

Question 9

What gene is lost at the 15q11-q13?

Answer 9

deletion on the long arm of chromosome 15 (at 15q11-q13) on the paternally inherited homolog. This causes the loss of the SNORD116 snoRNA that is likely involved in mRNA processing

Question 10

IDIC 15 inverted duplicated isodicentric 15q (supernumerary chromosome)

Answer 10

Full complement of 15, plus marker chromosome.

Question 11

15q interstitial duplication

Answer 11

Inheritance from mom gives phenotype of AUTISM with no dysmorphic features, hypotonia, seizures. Inheritance from dad = nothing. (imprinted gene)

Question 12

Angelman Syndrome, Phenotype:

Answer 12

mildly dysmorphic facial features which evolve with age, hypotonia in infancy progressing to spasticity in older patients, Intellectual Disability (ID), seizures, autism

Question 13

4 ways to get Angelman:

Answer 13

1) Large deletion
2) Mutation in UBE 3A
3) UPD (paternal disomy)
4) Imprinting defect