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Flashcards in Muscular Dystrophy Deck (37):
1

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

degeneration; weakness

2

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

false; in tissue too

3

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

Creatinuria

4

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

cellular membranes

5

These two muscular dystrophies are X-linked

duchenne muscular dystrophy and becker muscular dystrophy

6

X-linked muscular dystrophies primarily affect males or females?

males; female carriers are occasionally mildly affected

7

What is the incidence of Duchenne and Becker muscular dystrophies?

1 in 5200 live male births

8

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

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

9

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

2300; 79

10

Dystrophin is associated with the ____ of normal muscle

sarcolemma

11

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

absent; significantly reduced

12

Dystrophin interacts with what?

actin, syntrophin, B-dystroglycan, and others

13

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

increased osmotic fragility or permitting excessive Ca2+ influx

14

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

gross motor development

note: delays appear by second year of life

15

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

ages 3-5

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?

true

17

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

fat; connective tissue

18

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

iliotibial; hip; heal

19

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

12

20

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

20-30

21

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

ECG abnormalities and left ventricle myocardial fibrosis

22

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

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

23

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

IQ generally 1 standard deviation below average

24

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

true

25

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

50-100

26

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

20

27

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

false; strong evidence against a diagnosis

28

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

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

29

Muscle biopsy of a MD patient shows what?

variability in muscle fiber size including both small and hypertrophied fibers

30

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

regenerating; necrotic; segmental hypercontraction

31

___ gradually replaces lost muscle fibers in MD patients

Fat

32

_____ analysis is the definitive diagnosis

Dystrophin

33

Absence of dystrophin can be demonstrated by ____ ____ analysis

western blot

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

34

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

9; scoliosis

35

Prednisone improves what?

muscle mass and muscle function

36

What is the mechanism by which prednisone works?

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

37

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

92