Dystrophies & Myopathies (Mathews)

Question 1

Patient has fatiguability with repeated muscle action. Most likely location of disease is:

A. Anterior horn cell

B. Peripheral nerve

C. NM junction

D. Muscle

Answer 1

C

Question 2

Patient has symmetric pattern of proximal (or distal) weakness with normal sensation and DTRs. Most likely location of disease is:

A. Anterior horn cell

B. Peripheral nerve

C. NM junction

D. Muscle

Answer 2

D

Question 3

Patient has distal pattern of weakness, with decreased DTRs and sensation. Most likely location of disease is:

A. Anterior horn cell

B. Peripheral nerve

C. NM junction

D. Muscle

Answer 3

B

Question 4

Patient has fasciculations and diffuse pattern of weakness with normal sensation. Most likely location of disease is:

A. Anterior horn cell

B. Peripheral nerve

C. NM junction

D. Muscle

Answer 4

A

Question 5

Dominant limb girdle muscular dystrophies are type 1 or type 2?

Answer 5

They are type 1. Autosomal recessive are type 2.

Bonus: which muscular dystrophy is x-linked recessive?

*duchenne and becker

Question 6

1st test for diagnosing Duchenne muscular dystrophy

Answer 6

creatinine kinase - will be at least 5X normal (200), usually 5,000-30,000 IU/L

Question 7

Which of these is not a characteristic of muscular dystrophies that are due to abnormal nuclear organization or transcription?

A. Repeat expansion of nucleotides

B. Very high CK

C. Epigenetic modification of DNA

D. Mutations in the nuclear membrane

E. Progressive weakness that often involves non-muscle symptoms

Answer 7

B. Elevated CK is characteristic of MD that is due to membrane problems and results in proximal to distal weakness bilaterally.

Question 8

Which of these is not a characteristic of facioscalpulohumeral dystrophy (FSHD)?

A. Presents in teens or early adulthood

B. Symmetrical pattern of weakness

C. CK normal

D. Vision/hearing abnormalities associated with early onset

E. Hyperlordosis and scapular winging

Answer 8

B. Pattern of weakness is asymmetrical, most commonly.

Question 9

FSHD1 or FSHD 2: due to mutations in SMCHD1 leading to hypomethylation of DNA

Answer 9

FSHD 2

Question 10

FSHD 1 or FSHD 2: leads to the aberrant transcription of protein that is toxic to muscle fibers

Answer 10

BOTH! This protein is called Dux 4

Question 11

FSHD 1 or FSHD 2: results from a deletion of D4Z4 repeated elements on chromosome 4q

Answer 11

FSHD 1

Question 12

Which of the following is not a characteristic of congenital myopathies?

A. Inherited by any type of pattern - genetically complex

B. Onset of diffuse, slowly progressing weakness typically in infancy or prenatally

C. All muscles involved, including extra-ocular

D. Normal CK

E. Muscle biopsy significant for degeneration/regeneration of fibers

Answer 12

E. This is not a defining feature on muscle biopsy. The pathophysiology is mostly due to disorders of the contractile mechanism (sacromeric proteins, excitation-contraction coupling)

Question 13

Mutation of this protein is implicated in malignant hyperthermia, and is the most common single genetic cause of the congenital myopathies

Answer 13

RYR1. The ryanodine receptor plays a critical role in the release of calcium to initiate muscle contraction.

Question 14

Disease shown below in which there is a lack of mitochondria

Answer 14

central core disease

Question 15

mutation in thin filament genes that lead to the disease shown below:

Answer 15

Nemaline myopathy; the filaments do not form properly and accumulate within the muscle fiber

Question 16

Which TWO clinical signs would you NOT expect to see in someone with a congenital myopathy?

A. Hypotonia with diffuse weakness

B. Contractures (muscle rigidity)

C. Ophthalmoplegia (restricted eye movement)

D. Respiratory insufficiency

E. Scoliosis

F. Cognitive delays

G. Cardiomyopathy

Answer 16

F and G. These are uncommon in congential myopathies.

Question 17

congenital myopathy that is characterized by type I skeletal muscle fibers that are significantly smaller than type II skeletal muscle fibers

Answer 17

congenital fiber type disproportion

Question 18

disease caused by an epigenetic modification that results in a “toxic” transcript

Answer 18

FSHD

Question 19

group of generally non-progressive, heterogenous, inherited diseases that affect the contractile mechanism of the muscle cell and typically present at birth or infancy

Answer 19

congenital myopathies

Question 20

disease caused by deficiency of dystrophin, a sarcolemmal membrane related protein, resulting in a leaky membrane

Answer 20

Duchenne/Becker muscular dystrophy