Chromosomal Abnormalities

Question 1

What is the incidence of chromosomal abnormalities in live-born infants?

Answer 1

1 in 150

Question 2

What are typical craniofacial appearances in Down syndrome?

Answer 2

Round face and flat nasal bridge. Upslanted palpebral fissues, epicanthic folds, brushfield spots, apparent macroglossia, flat occiput, third fontanelle, small low set ears

Question 3

What non-craniofacial anomalies are associated with Down Syndrome at birth?

Answer 3

Short neck, single palmar creases, hypotonia, congenital heart defects, duodenal atresia, Hirschsprung disease

Question 4

What later medical problems are associated with Down Syndrome?

Answer 4

Delayed milestones and learning difficulties, increased infections, visual impairment, leukaemia, atlanto-axial instability, hypothyroidism, coeliac disease, epilepsy, Alzheimer’s

Question 5

What is a Robertsonian translocation?

Answer 5

Chromosomes break at their centromeres and long arms join to other long arms; effect is Down syndrome with 46 chromosomes

Question 6

What is mosaicism in Down syndrome?

Answer 6

Chromosomally normal zygote but trisomy occurs in early mitosis

Question 7

What are the clinical features of Edwards (trisomy 18) syndrome?

Answer 7

Prominent occiput, small mouth/chin, short sternum, overlapping fingers, “rocker-bottom” feet

Question 8

What are the clinical features of Patau (trisomy 13) syndrome?

Answer 8

Scalp/brain defects, microphthalmia, cleft lip/palate, polydactyly

Question 9

What are the clinical features of Turner syndrome?

Answer 9

Neonatal lymphoedema, spoon-shaped nails, short stature, neck webbing, widely spaced nipples, coarctation of the aorta, delayed puberty, hypothyroidism

Question 10

What are the clinical features of Klinefelter (XXY) syndrome?

Answer 10

Infertility, hypogonadism, gynaecomastia, tall stature, some educational/psychological problems

Question 11

What are the clinical features of cri du chat (5p deletion) syndrome?

Answer 11

Characteristic cry, LBW, developmental delay, behavioural problems, drooling, small head and jaw, wide eyes, VSD/ASD

Question 12

What are the clinical features of DiGeorge (22q11 deletion) syndrome?

Answer 12

Neonatal hypocalcaemia, conotruncal malformations, hypoplastic thymus (T cell immunodeficiency), schizophrenia

Question 13

What are the clinical features of Williams (7q11 deletion) syndrome?

Answer 13

“Elfin” facial features, heart murmurs, supravalvular aortic stenosis, hypercalcaemia, malfunctioning auditory nerve, strabismus, developmental delay