Genetic Diseases

Question 1

What pattern of inheritance does Duchenne muscular dystrophy (DMD) follow?

Answer 1

X-linked recessive

Question 2

Where is delay in motor movement and muscle weakness usually present in DMD?

Answer 2

Pelvic and shoulder girdles

Question 3

When does death typically occur in DMD and why?

Answer 3

Between 20 and 30 years old

Cardiorespiratory muscle dysfunction

Question 4

List some clinical features of DMD

Answer 4

Thigh muscle wasting
Gower sign
Exaggerated lumbar lordosis

Question 5

Which protein is deficient in DMD? Why is it important?

Answer 5

Dystrophin

Connects contractile cell elements together - without it muscles can’t renew or operate

Question 6

What type of genetic abnormalities affects the dystrophin gene in DMD?

Answer 6

Large deletions (70%)
Point mutations, small insertions and deletions (30%)

Question 7

List investigations for DMD

Answer 7

Serum CK (raised)
Electromyography
Muscle biopsy
Genetic screen

Question 8

Asymptomatic carriers of the DMD gene can have raised serum CK. True/False?

Answer 8

True

Question 9

When is the usual onset for Huntington disease?

Answer 9

Between 30-50 years old but can vary

Question 10

List the clinical features of Huntington disease

Answer 10

Involuntary, semi-purposeful movements
Clumsiness
Irritability/agitation
Apathy
Delusions/hallucinations
Depression

Question 11

What inheritance pattern does Huntington disease follow?

Answer 11

Autosomal dominant

Question 12

What happens to the basal ganglia in the brain in Huntington disease?

Answer 12

Caudate nucleus atrophy

Question 13

What is the molecular genetic defect in Huntington disease?

Answer 13

Trinucleotide CAG repeat expansion (extra glutamine produced)

Question 14

Alzheimer disease is a multifactorial genetic disease. Which inheritance patterns can it follow?

Answer 14

Autosomal dominant (10%)
Trisomy 21 (with Down syndrome)