Muscle Channelopathies

Question 1

Myotonia congenita - clinical features

Answer 1

sustained muscle tension in any skeletal muscle, but especially muscles in the legs.

Question 2

Frequency of myotonia congenita

Answer 2

1 in 100,000 people worldwide, more common in scandinavia (1 in 10,000)

Question 3

Myotonia congenita - gene

Answer 3

CLCN1

Question 4

Mytonia congenita - inheritance

Answer 4

Thomsen disease is AD, Becker is AR

Question 5

Myotonia congenita - etiology

Answer 5

Mutations in CLCN1 alter the structure and function of chloride channels, resulting in a reduction of chloride ions in skeletal muscles

Question 6

Paramyotonia congenita - clinical features

Answer 6

individuals experience spells of muscle stiffness or myotonia, can be triggered by cold or exercise

Question 7

Paramyotonia congenita - frequency

Answer 7

1 in 100,000

Question 8

Paramyotonia congenita - gene

Answer 8

SCN4A

Question 9

Paramyotonia congenita - inheritance

Answer 9

AD

Question 10

Paramyotonia congenita - etiology

Answer 10

Mutations in SCN4A gene alters the structure of sodium channels and they cannot regulate the flow of sodium into muscle cells

Question 11

Hyperkalemic periodic paralysis - clinical features

Answer 11

episodes of extreme muscle weakness or paralysis, usually in arm and leg muscles. Episodes increase in frequency until mid-adulthood

Question 12

Hyperkalemic periodic paralysis - frequency

Answer 12

1 in 200,000

Question 13

Hyperkalemic periodic paralysis - gene

Answer 13

SCN4A

Question 14

Hyperkalemic periodic paralysis - inheritance

Answer 14

AD

Question 15

Hyperkalemic periodic paralysis - etiology

Answer 15

Mutations in SCN4A causes sodium channels to stay open too long, allowing too much sodium into cells, triggering the body to dump potassium into the blood

Question 16

Hypokalemic periodic paralysis - clinical features

Answer 16

episodes of extreme muscle weakness and temporary paralysis of arms and legs, which can last between a few hours to days

Question 17

Hypokalemic periodic paralysis - frequency

Answer 17

1 in 100,000

Question 18

Hypokalemic periodic paralysis - gene

Answer 18

CACNA1S, SCN4A, KCNJ2

Question 19

Hypokalemic periodic paralysis - inheritance

Answer 19

AD

Question 20

Hypokalemic periodic paralysis - etiology

Answer 20

SCN4A creates sodium channels, CACNA1S creates calcium channels, and KCNJ2 creates inward rectifier potassium channels

Question 21

Andersen-Tawil Syndrome - clinical features

Answer 21

Periods of muscle weakness and paralysis, cardiac arrhythmias and prolonged QT interval, distinctive facial features and skeletal abnormalities

Question 22

Andersen-Tawil Syndrome - frequency

Answer 22

1 in a million people

Question 23

Andersen-Tawil Syndrome - gene

Answer 23

KCNJ2 accounts for about 60%

Question 24

Andersen-Tawil Syndrome - inheritance

Answer 24

AD with a large de novo rate

Question 25

Andersen-Tawil Syndrome - etiology

Answer 25

KCNJ2 encodes inward rectifier potassium channel 2

Question 26

Management for muscle channelopathies

Answer 26

Participate in low intensity and low resistance exercises, annual visits to cardiologists, propofol & non-depolarizing anesthetics, MRI of leg muscles every 1-3 years, thyroid function tests

Question 27

What things should people with muscle channelopathies avoid?

Answer 27

opiods and ACE-inhibitors, fasting, foods high in carbs or potassium, exposure to cold

Question 28

Treatment for muscle channelopathies

Answer 28

aldosterone antagonists (potassium sparing), thiazides (potassium wasting), potassium supplements, carbonic anhydrase inhibitors, sodium channel blockers

Question 29

Genetic testing for muscle channelopathies

Answer 29

molecular genetic testing (gene-targeted testing, comprehensive genomic testing) and test levels of serum creatine kinase concentration