Muscular Dystrophies

Question 1

what are 4 criteria that distinguish muscular dystrophies from other neuromuscular disease?

Answer 1

1. primary myopathy
2. genetic basis
3. progressive course
4. degeneration and death of muscle fibers occur at some stage

Question 2

Mutation the dystrophin gene causes what 2 disorders?

Answer 2

Duchenne Muscular Dystrophy (deletion of gene)

Becker muscular dystrophy (gene mutation)

Question 3

What type of inheritance of Duchenne Muscular Dystrophy?

Answer 3

X-linked recessive

Question 4

progressive weakness - begins in pelvic girdle, progresses superiorly

intellectual impairment
pseudohypertrophy of the calves (fatty replacement)
YOUNG children
hip waddle!

Answer 4

Duchenne muscular dystrophy

Question 5

What is gower’s sign?

Answer 5

children need to “walk” their hands up their legs to stand up - Duchenne Muscular Dystrophy

Question 6

what is a fatal complication of duchennes muscular dystrophy? Sx?

Answer 6

Dilated Cardiomyopathy
Sx: Arrhythmia, Fatigue, Edema

addn’l causes of death: respiratory failure, pneumonia, aspiration/airway obstruction

Question 7

What are screening signs of Duchenne’s Muscular dystrophy? Dx?

Answer 7

Greatly elevated:

1. Creatine Kinase
2. Aldolase, Aspartate aminotransferase

Dx with dystrophin gene mutation via Western Blot

Question 8

What is Becker Muscular Dystrophy?

Answer 8

Similar to DMD, but
dystrophin is present but at decrease fxn
milder severity
onset is later
slower rate of progression 
lower rate of learning disabilities

Question 9

Muscle dystrophy that mainly affects hip and shoulder girdle

distal muscles eventually become dystrophic/weak

may develop hypertrophy of calves, ankle contractures

Answer 9

Limb-Girdle Muscle dystrophy

Question 10

What is the genetic cause of Limb-Girdle Muscle dystrophy 2B?

Answer 10

mutation in the Dysferline gene

–needed for muscle membrane repair

Question 11

initial complaint of lower back pain
Lordotic posture (gluteal weakness)
normal intellectual level

Answer 11

Limb-Girdle Dystrophy

Question 12

What are two forms of Charcot-Marie Tooth?

Answer 12

CMS-1: demyelinating form

CMS-2: axonal form of CMT disease

Question 13

What are Sx of Charcot-Marie Tooth?

Answer 13

Dont affect children until late childhood/adolescence
Affects the Peroneal and Tibial N first
Anterior Tib weakness (clumsy, falls alot)
weak dorsiflexion = FOOT DROP
Pes Cavus foot deformities (HIGH ARCH)

Question 14

what is the Dx of Charcot-Marie Tooth?

Answer 14

EMG (nerve conduction is reduced)

Sural Nerve Biopsy = Dx

Question 15

a/w holoproscencephaly, lissencephaly
agenesis of corpus callosum, cerebellar hypoplasia

Birth: contractions, hypotonic, thin muscle mass, poor head control, facial muscles not involved

Answer 15

Congenital Muscle dystrophy

Question 16

Myotonic Musc Dys has what type of inheritance and gene mutation?

Answer 16

Autosomal dominant

protein kinase gene (DMPK) - leads to abnormal expression of myotonin protein kinase

Question 17

Inverted v shaped upper lip
thin cheeks
scalloped concave temporalis muscles
narrow head
high arches palate

Answer 17

Myotonic MD

Question 18

What is the inheritance and mutation of Emery-Dreifuss MD?

Answer 18

X-linked recessive
defective EMD/EDMD - emerin

this protein is in the inner nuclear membrane and stabilizes the nuclear membrane against the mechanical stresses that occur during muscular contraction

Question 19

Scapuloperoneal
Scapulohumeral muscular dystrophy
dilated cardiomyopathy

Answer 19

Emery-Dreifuss MD

Question 20

What are lab finding in emery-dreifuss MD?

Answer 20

Moderately elevated CK

muscle biopsy - emerin deficiency