Muscular Dystrophy

Question 1

The muscular dystrophies are a class of inherited disorders of metabolism characterized by muscle ____ and ____

Answer 1

degeneration; weakness

Question 2

True or false? in muscular dystrophies, symptoms are only expressed in muscle

Answer 2

false; in tissue too

Question 3

_____ is a characteristic of all of the muscular dystrophies. Serum creatine kinase activity is elevated in many of the muscular dystrophies

Answer 3

Creatinuria

Question 4

Defects in the structure and function of ____ _____ appear to be associated with all of the muscular dystrophies

Answer 4

cellular membranes

Question 5

These two muscular dystrophies are X-linked

Answer 5

duchenne muscular dystrophy and becker muscular dystrophy

Question 6

X-linked muscular dystrophies primarily affect males or females?

Answer 6

males; female carriers are occasionally mildly affected

Question 7

What is the incidence of Duchenne and Becker muscular dystrophies?

Answer 7

1 in 5200 live male births

Question 8

What is the primary defect in Duchenne and Becker muscular dystrophies?

Answer 8

dystrophin; gene is deleted from the short arm of the X chromosome

Question 9

The Dystrophin gene is one of the largest recognized to date: ____kb, ____ exons

Answer 9

2300; 79

Question 10

Dystrophin is associated with the ____ of normal muscle

Answer 10

sarcolemma

Question 11

In Duchenne patients, dystrophin is ____; in Becker patients, dystrophin is ____ _____

Answer 11

absent; significantly reduced

Question 12

Dystrophin interacts with what?

Answer 12

actin, syntrophin, B-dystroglycan, and others

Question 13

Deficiency in Dystrophin may affect the integrity of the plasma membrane resulting in what?

Answer 13

increased osmotic fragility or permitting excessive Ca2+ influx

Question 14

A clinical sign of MD is a delay in what type of development?

Answer 14

gross motor development

note: delays appear by second year of life

Question 15

When do difficulty walking, running, climbing stairs, and riding a tricycle appear in MD patients?

Answer 15

ages 3-5

Question 16

Progressive weakness with waddling gait, lordosis, difficulty rising from a sitting supine position (Gower’s sign) are all signs of MD. True or false?

Answer 16

true

Question 17

Calf muscle hypertrophy occurs in MD patients when ____ and ____ ____ completely replace muscle

Answer 17

fat; connective tissue

Question 18

Scoliosis; contractors of ____ bands, ___ joints and ___ cords, and joint deformities are seen in MD patients

Answer 18

iliotibial; hip; heal

Question 19

Inability to ambulate by about age ____ mild mental retardation is seen in MD patients

Answer 19

12

Question 20

Respiratory and accessory muscles involved in end stage with cardiomegaly usually occurs at age ___-___ in MD patients

Answer 20

20-30

Question 21

In regards to organ systems in MD patients, what abnormalities are seen in the cardiac system?

Answer 21

ECG abnormalities and left ventricle myocardial fibrosis

Question 22

In regards to organ systems in MD patients, what abnormalities are seen in the GI system?

Answer 22

pathologic involvement of smooth muscle leading to acute gastric dilation: vomiting, pain, and dissension which may lead to death

Question 23

In MD patients, what abnormalities are seen in the CNS?

Answer 23

IQ generally 1 standard deviation below average

Question 24

In MD patients Creatine Kinase has marked elevation in first years of life, before obvious clinical manifestations. True or false?

Answer 24

true

Question 25

CK levels of ___-____ X normal are expected by 3 years of age

Answer 25

50-100

Question 26

CK levels drop about ____% after age 3 due to decreasing healthy muscle tissue

Answer 26

20

Question 27

CK less than 10 X normal at any age is strong evidence for a diagnosis of MD

Answer 27

false; strong evidence against a diagnosis

Question 28

Electromyography of MD patients typically indicates a myopathy characterized by what?

Answer 28

early recruited, short-duration, low amplitude, polyphasic motor unit potentials

Question 29

Muscle biopsy of a MD patient shows what?

Answer 29

variability in muscle fiber size including both small and hypertrophied fibers

Question 30

Muscle biopsy in MD patients shows small groups of ____ and ____ fibers and large, opaque, darkly stained fibers are frequent as a result of _____ _____

Answer 30

regenerating; necrotic; segmental hypercontraction

Question 31

___ gradually replaces lost muscle fibers in MD patients

Answer 31

Fat

Question 32

_____ analysis is the definitive diagnosis

Answer 32

Dystrophin

Question 33

Absence of dystrophin can be demonstrated by ____ ____ analysis

Answer 33

western blot note: prenatal testing of amniotic fluid or chorionic villus sampling using cDNA probes is also available

Question 34

By age ___, most boys require leg braces and surgery may be required to reduce _____

Answer 34

9; scoliosis

Question 35

Prednisone improves what?

Answer 35

muscle mass and muscle function

Question 36

What is the mechanism by which prednisone works?

Answer 36

may act through suppression of cytotoxic T-lymphocytes thus reducing invasion of muscle tissue by lymphocytes

Question 37

In regards to a myoblast tranfer study in 1995, ___% of the subjects showed no improvement in muscle strength

Answer 37

92