X-linked Recessive Disorders

Question 1

Are female carriers of X-linked recessive alleles affected by disease?

Answer 1

Female carriers can be variably affected depending on the percent inactivation of the X chromosome carrying the mutant vs. normal gene.

Question 2

Duchenne muscular dystrophy is typically due to…

Answer 2

Frameshift mutations that lead to production of truncated dystrophin protein and skeletal muscle fragility

Question 3

Muscle weakness in Duchenne muscular dystrophy typically begins in…

Answer 3

Pelvic girdle muscles and progresses superiorly.

Question 4

In DMD, pseudohypertrophy of calf muscles is due to…

Answer 4

Fibrofatty replacement of muscle

Question 5

Describe the Gower maneuver.

Answer 5

Pts use upper extremities to help them stand up.

Question 6

A common cause of death in DMD is…

Answer 6

Dilated cardiomyopathy

Question 7

Onset of symptoms in DMD occurs…

Answer 7

Before 5 years of age

Question 8

What is the normal function of dystrophin?

Answer 8

It connects the intracellular cytoskeleton (actin) to the transmembrane proteins alpha- and beta-dystroglycan, which are connected to the extracellular matrix.

Question 9

Loss of dystrophin function results in…

Answer 9

Myonecrosis

Question 10

Which biochemical abnormalities are seen in patients with DMD?

Answer 10

Increased CPK and aldolase levels in serum

Question 11

Be Wise, Fool’s GOLD Heeds silly HOpe.

Answer 11

1. Bruton agammaglobulinemia
2. Wicket-Aldrich syndrome
3. Fabry disease
4. G6PD deficiency
5. Ocular albinism
6. Lesch-Nyhan syndrome
7. Duchenne (and Becker) muscular dystrophy
8. Hunter syndrome
9. Hemophilia A and B
10. Ornithine transcarbamylase deficiency