Intro To Learning Disorders

Question 1

Clinical dysmorphology is a branch of clinical genetics concerned with the diagnosis and interpretation of what three types of structural defects?

Answer 1

1. Deformation: caused by mechanical force and often resolved if force is removed
2. Disruption: caused by breakdown of normal development (e.g. Amniotic bands - constrict supply of blood to digits resulting in amputation)
3. Malformation: caused by intrinsic developmental defects (e.g. Isolated cleft lip and/or palate)

Question 2

What is the definition of a syndrome?

Answer 2

A non-random association of multiple malformations or alterations in body form that are pathogenetically related

> 4000 syndromes are listed on the Winter-Baraitser dysmorphology database

Question 3

What is Gestalt?

Answer 3

Diagnosis by immediate pattern recognition I.e. Just based on appearance

Question 4

What are some common abnormalities of the:

• Face
• Ears
• Perioocular region
• Ocular region
• Perioral region

Answer 4

• facial asymmetry/mid face hypoplasia
• skin tags/pits
• abnormal eye spacing (hyper/hypotelorism), upward/downward sloping palpebral fissures
• epicanthic folds/coloboma (iris)
• cleft lip/smooth philtrum and thin upper lip (fetal alcohol syndrome)

Question 5

Short stature that is deemed pathologic and disproportionate can be caused by what?

Answer 5

Skeletal dysplasias

Question 6

What are the terms for shortening of the

• proximal limbs
• distal limbs
• digits

Answer 6

• rhizomelic
• mesomelic
• acromelic

Question 7

What is polydactyly and what is the difference between pre- and post-axial? What is syndactyly?

Answer 7

Polydactyly is the occurrence of supernumerary digits. Pre-axial refers to extra digits in the thumb side, post-axial on the fifth finger side

Syndactyly is where the fingers or toes grow/join together to a degree

Question 8

What are some of the problems associated with the diagnosis of syndromes?

Answer 8

• can be extremely variable
• may be very rare
• one syndrome can be caused by different genes (heterogeneity)
• one gene can be the cause of different syndromes
• genetic tests have limitations

Question 9

Why should we do dysmorphology?

Answer 9

• identification of new syndromes
• identification of genes/chromosomal regions responsible for specific syndromes
• understanding of specific pathogenetic mechanisms and gene pathways