Williams Syndrome Lorraine Potocki, M.D., F.A.C.M.G.ProfessorDepartment of Molecular and Human GeneticsBaylor College of MedicineTexas Children’s Hospital

What is a syndrome?

Collection of physical, behavioral, and medicalfeatures which are common to individuals who share the same genetic or chromosomal complement.

Williams Syndrome

Similar facial appearanceHigh calcium levelsCardiovascular disease: Supra-valvular aortic stenosis, etc.Social personality with expressive language skills to matchVery poor visuospatial skillsAffinity for music

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PHOTOS: GeneReviews® [Internet]. Adam MP, Ardinger HH, Pagon RA, et al., editors. Seattle (WA): University of Washington, Seattle; 1993-2019.

Supravalvular Aortic Stenosis

Elastin Stain of Blood Vessel

Normal

Williams Syndrome

Elastin Arteriopathy

Genes, Language, and the Nature of Scientific Explanations: The Case of Williams Syndrome. Cognitive Neuropsychology 29(1-2):123-48 · February 2012

What is the genetic basis of Williams syndrome?:

Deletion of chromosome 7q11.23Including the elastin gene and others.

Typically NOT inherited.Some parents have an inversion (as do 6% of population)

Deletion occurs because of genomic structure.Deletions and duplications occur THROUGHOUT the genome.

p

q

~20,000 genespackaged on 23 pairs of chromosomes

Karyotype & FISH

7

pq

Deletion 7q11.23

This deletion is NOT visible on G-banded chromosome analysis,but can be detected by FISH as an absent signal.

ELN+ othergenes

Laboratory DiagnosisKaryotype vs FISH vs Microarray

Chromosomal microarray (also known as CMA or aCGH) is greatly improving the rate of diagnoses.

CMA is the appropriate test in 2019.

1

2

A

D '

A '

D

C

B

C '

B '

No copy of7q11.23

D

C

B

A

ELND '

C '

B'

A'Egg orSperm cell

I LIKE TO SWIM IN THE OCEAN BUT I DO NOT

LIKE TO SWIM IN THE POOL

I LIKE TO SWIM IN THE OCEAN BUT I DO NOT LIKE TO SWIM IN THE POOL

I LIKE TO SWIM IN THE POOL

Deletion

Occurrence and RecurrenceThe vast majority of

7q11.23 deletionsoccur de novo, orsporadically.

However, when a personhas Williams syndromethe risk to have a child with same deletion is 50%