Msk 6

Question 1

What are the most common types of muscular dystrophies?

Answer 1

X-linked

Question 2

What is the most common x-linked muscular dystrophy?

Answer 2

Duchenne’s muscular dystrophy (DMD)

Question 3

What gene is affected in x-linked muscular dystrophies, and where is it located?

Answer 3

Dystrophin gene

• dystrophin-glycoprotein complex stabilizes muscle cell during contraction

Xp21

Question 4

1 in 3500 male births (ONLY MALES)

Delayed motor development

Progressively severe muscle wasting

Wheelchair confinement by 12 y/o

Early death due to respiratory failure

Answer 4

Duchenne’s Muscular Dystrophy

Question 5

Muscle disorders due to genetic defects in energy metabolism

Answer 5

Metabolic myopathies

Question 6

Myasthenia Gravis is what type of disease?

Answer 6

Neuromuscular junction disease

Question 7

What is the mechanism behind Myasthenia Gravis?

Answer 7

Auto-antibodies against Ach receptors

May have ocular MG associated with ptosis and diplopia

Symptoms of general MG tend to worsen throughout the day (diural fluctuation) and provoked by exertion.

Question 8

This disease is characterized by auto-antibodies against voltage-gated Ca²⁺ channels on the presynaptic terminal.

Many of these patients also have lung cancer.

Answer 8

Lambert-Eaton Myasthenic Syndrome (LEMS)

Question 9

What is Malignant Hyperthermia?

Answer 9

Autosomal dominant genetic disease that causes disturbances in Ca²⁺ homeostasis in skeletal muscle.

Defect in the SR Ca²⁺ Release Channel (RYR)

Anesthetics cause uncontrolled release of Ca²⁺ from the SR

Question 10

Name the 3 neuromuscular junction diseases mentioned in this lecture.

Answer 10

Myasthenia Gravis (MG)

Lambert-Eaton Myasthenic Syndrome (LEMS)

Malignant Hyperthermia (MH)