Genetics

Question 1

CF

Answer 1

Defect of cellullar chloride transport. Meconium ileus, Lung infections: acute, chronic, Pancreatic insufficiency, Diagnosis: Immunoreactive trypsin (first 6 wks), sweat test, genotyping

Question 2

SCD

Answer 2

SCDAbnormal HB gene, Sickle commonest UK, Sickling, Pain+++, Cold, dehydration, infections, Jaundice, stroke, leg ulcers, eyes, kidneys, African, Medicterranean, Middle-East, Indian, Anaesthetic issues

Question 3

Tay-sachs

Answer 3

Progressive, genetic, lysosomal storage disease. Hexosaminidase A (hex-A) deficiency results in the build up of lipid GM(2) ganglioside, esp. in nerve cells in the brain. Baby usually develops normally until about 6 months of age. Progresive neurological deterioration. Usually fatal by 3-5 years. 1 in 25 Ashkenazi Jews and 1 in 250 of the general population are carriers.

Question 4

how are babies screened?

Answer 4

clinical exam, hearing and dried blood spot

Question 5

what dow e screen for?

Answer 5

Phenylketonuria (PKU), Congenital Hypothyroidism (CHT), Sickle cell disorders (SCD), Cystic fibrosis (CF), MCADD – medium chain acyl-CoA dehydrogenase deficiency
And now: Homocysteinuria, Isovaleric acidaemia, Maple syrup urine disease, Glutaric aciduria type 1

Question 6

Phenylketonuria (PKU)

Answer 6

Affects approximately 1 in 10,000 babies in UK (ie about 80 born each year)

• Recessive condition – biochemical screen
  - carriers not identified
• Babies with condition are unable to break down phenylalanine (an amino acid in protein)
• Untreated babies develop serious, irreversible, mental disability
• Early treatment with a strictly controlled diet prevents disability
• Treatment should start by 21 days of age

Question 7

Congenital Hypothyroidism (CHT)

Answer 7

1 in 4,000 babies UK
1 in 10 cases inherited – hormone test
carriers not identified
- Not enough thyroxine
- Untreated babies -> serious, permanent, physical and mental disability
- Early treatment with thyroxine tablets prevents disability
- Treatment should start by 21 days of age

Question 8

Medium chain Acyl-CoA Dehydrogenase Deficiency (MCADD)

Answer 8

Recessive inherited condition – carriers not identified
Babies with MCADD cannot easily break down fat to make energy for the body
Serious life-threatening symptoms can occur quickly in babies not feeding well or unwell
Mean age at first presentation is14 months. 25% mortality rate
Treatment to prevent metabolic crisis: avoid fasting and monitor frequency of meals
Emergency regime: glucose polymer (maxijul) and IV dextrose