genetics: multi-system disease

Question 1

where do germline genetic variations present?

Answer 1

in every cell

Question 2

modes of inheritance in multi-system disorders?

Answer 2

chromosomal:
- numerical
- structural (translocations, deletions)

single gene disorders

• autosomal dominant/recessive
• x linked

multifactorial

• polygenic
• environmental

Question 3

why is there multi-system involvement with gene defects?

Answer 3

several genes have diverse functions

single genes widely expressed in different tissues

Question 4

neurofibromatosis type 1

Answer 4

autosomal dominant (17q gene)

diagnostic criteria: (Chase Bank LOANS)

• Café au lait spots (6 or more)
• Bony abnormalities (pseudoarthrosis, scoliosis, thinning of long bone cortex)
• Lisch nodules (specks in iris)
• Optic glioma
• Axillary freckling
• Neurofibromas (2 or more)
• Sister (1st degree relative)

Question 5

neurofibromatosis type 2

Answer 5

occurs on chromosome 22

Chromosome Twenty Two

• Cafe au lait spots
• Two acoustic neuromas (bilateral)
• Tumours (CNS and spinal)

Question 6

tuberous sclerosis

Answer 6

autosomal dominant (genes TSC1/TSC2)

hamartomas in different organs

classic triad: epilepsy, learning difficulties, skin lesions

screening: clinical examination, cranial MR scan, renal ultrasound, echocardiogram

Question 7

myotonic dystrophy

Answer 7

autosomal dominant

MyoToniC Dystrophy

• Muscle weakness/myotonia
• cTg repeats - anticipation
• Cataracts - bilateral
• Diabetes,