Devlopmental delay/Learning disability

Question 1

What factor is the incidence of trisomy 21 due to meiotic non-disjunction related to?

Answer 1

Maternal age

Question 2

Apart from meiotic non-disjunction (accounting for 94%), what other ways can a person have trisomy 21?

Answer 2

Translocation - extra chromosome is joined onto another chromosome (usu. 14/15/21/22)
Mosaicism - some cells are normal and some have T21 (milder phenotype)

Question 3

What are people with Down’s syndrome at increased risk of?

Answer 3

Greater risk of infection, leukaemia, hypothyroidism, diabetes, early-onset Alzheimer’s dementia, epilepsy, visual impairment from cataracts/squint/myopia, hearing problems, coeliac disease. Males have reduced fertility

Question 4

What is the average life expectancy of someone with Down’s syndrome?

Answer 4

58 years

Question 5

What are the 2 types of squint?

Answer 5

Concomitant - common. Usually due to a refractive error in one or both eyes. Correction with glasses, or if needed, surgery on the ocular muscles. The squint is constant in all directions of gaze
Paralytic - must rule this out as it could be due to a SOL. Varies with direction of gaze due to eye nerve palsy.

Question 6

What direction will an affected eye be looking if there is a CN3 (oculamotor nerve) palsy?

Answer 6

Down and out

Question 7

How is a squint/lazy eye managed?

Answer 7

A squint may lead to the affected eye becoming a ‘lazy eye’ - ambluopia develops as the brain learns to not interpret information from this eye. To correct this, a patch covering the good eye should be worn to encourage the squint eye to take up the main job of vision

Question 8

What is the inheritance pattern of Fragile X syndrome?

Answer 8

X-linked recessive disorder - excess genetic material on the X chromosome

Question 9

How does Fragile X syndrome affect IQ?

Answer 9

Boys have moderate-to-severe learning difficulty (20-80; average IQ = 50).
Female carriers usually also have some degree of learning difficulty