Skeletal Muscle / PNS Pathology

Question 1

What do degenerating vs regenerating neurons in the periphery look like?

Answer 1

Degeneration – Macrophages invading numerous nuclei surrouding the axons
Regeneration – Enlarged Nuclei and blue cytoplasm

Question 2

What is a unique chracteristic of re-innervation of muscle fibers?

Answer 2

–Grouping of similar type of fibers, contrary to mixed types throughout

Question 3

How can you tell neurogenic or myopathic muscle reactions?

Answer 3

Neurogenic – angulated fibers, nuclear clumps, NO Necrosis or inflammation
Myopathic – round fibers - central nuclei - NECROSIS
EMG can be used for testing

Question 4

What syndrome causes degradation of upper and lower motor neurons that progresses over time with emotion lability?

Answer 4

Amyotrophic Lateral Sclerosis

Question 5

What are the most common neurons affects in ALS?

Answer 5

• -Motor Neurons

- - Anterior Horn – atrophy of nerve roots

Question 6

What is the most likely diagnosis of a 7 year old with trunkal/proximal muscle weakness, progressive dysphasia, and needing help to breath on respiratory due to the proximal weakness?

Answer 6

Spinal Muscular Atrophy

• -Deletion of SMN1 (Survival Motor Neuron)
• -Autosomal Recessive – two deletions required

Question 7

What is the protein that maintains integrity of muscle cells from physical stress and torsion?

Answer 7

– Dystrophin

if missing, then any action of the muscle can induce damage

Question 8

If a 9 year old male experiences progressive proximal muscle weakness, wide gait, difficulty with Gower’s maneuver, winged scapula, and elevated CK levels in serum?

Answer 8

Duchenne Muscular Dystrophy

• • Very minimal amount of Dystrophin present
• • Upregulated Utropin in muscles (to compensate)

Question 9

If a 64 year old male presents with years of progressive proximal weakness, what might be a likely diagnosis?

Answer 9

Becker Muscular Dystrophy

–Abnormal Dystropin and reduced quantity

Question 10

How are Duchenne and Becker muscular dystrophies similar?

Answer 10

Both are X-linked Recessive

Question 11

If there is a finding of expanded CTG repeats of the DMPK gene, what might be the disorder?

Answer 11

Myotonic Dystrophy

–Dysfunction of the

Question 12

What is the most common muscular dystrophy in adults?

Answer 12

Myotonic Dystrophy

• -Autodominant
• -Genetic Anticipation, more repeats pass on

Question 13

What are unique exam findings with Myotonic Dystropy?

Answer 13

• Difficulty Releasing Grip – impaired Cl- conduction
• Distal hands and feet weakness
• Elongated face - temporal wasting
• cardiac arrthymias

Question 14

How is Myotonic Dystrophy different from other dystrophies?

Answer 14

Myotonic – there is nothing wrong with Dystrophin

• • no destruction of muscle fibers
• • internal nucleation

Question 15

How do mitocondrial myopathies lead to disease?

Answer 15

• -Due to inefficient production of ATP and then the cell is unable to function normally and oxidative damage also builds up, b/c no energy to combat them.
• -Causes degradation of the cells

Question 16

What condition is associated with mitochondrial myopathy?

Answer 16

MELAS
Mito Myopathy, Encephalopathy, Lactic acidosis, stroke-like episodes
Why? – Not enough ATP being produced and cells become ischemic intermittently, thus reason for lactic acidosis

Question 17

What are the main clinical criteria for MELAS?

Answer 17

Stroke-like episodes, non-vascular in origin
Encephalopathy – neurodegenerative
Lactic Acidosis, ragged red fibers

Question 18

What are the most common types of glycogen storage diseases?

Answer 18

Myopathic Form – problem in muscles and exercise intolerance with cramps and myoglobinuria
Generalized Forms – Pompe’s Disease
–effects many organs, mostly heart - early death

Question 19

What would a main histologic finding be of various tissues with Pompe’s Disease?

Answer 19

Vacuoles filled with glycogen-products

- pools of glycogen

Question 20

Which inflammatory myopathy is associated with females, erythematous lesions over the knuckles and rash on the eyes?

Answer 20

Dermatomyositis

Question 21

What kind of immune response is responsible for Polymyositis?

Answer 21

CD8+ T cells – attacking muscle fibers

• -Symmetric proximal muscle weakness
• -associated with other auto immune diseases

Question 22

What is the underlying pathology for Dermatomyositis?

Answer 22

Microvascular being attacked by complement and antibodies
Muscle Biopsy: Perifascicular Atrophy in the muscle
(Since that part of the muscle fibers only have single blood supply, so they die, deeper have dual)

Question 23

If a 56 year old male is evaluated by muscle biopsy and found to have rimmed vacuoles and tubulofilamentous inclusions, what might be a clinical symptom?

Answer 23

Dysphasia

–Deep finger flexor atrophy and quad atrophy

Question 24

Which of the inflammatory myopathies can be found in children?

Answer 24

Dermatomyositis

Question 25

What might happen if a patient has prolonged use of high dose steroids?

Answer 25

• -Proximal Muscle Weakness

- -Atrophy of Type 2B Fibers

Question 26

What are the two types of peripheral nerve pathologies?

Answer 26

Neuronopathy – Axon degenerating back proximally

Wallerian – focal lesion degenerates distally

Question 27

Where does Mononeuritis Multiplex usually affect?

Answer 27

Vasculitis
–Ulnar nerve – hand weakness
–Distal sciatic – foot drop
Dx – via nerve biopsy with inflammation

Question 28

What are the common manifestations of Leprosy?

Answer 28

• Exposure to Mycobacterium leprae
• Usually coming from another country previously in their life and get it years later (incubation)
• Hypopigmented Lesions
• Neuromas

Question 29

What pathology common has an “onion bulb” formation on histology?

Answer 29

Charcot Marie Tooth Type 1A

• -gradual myelin loss
• -autodominant PMP22 mutation/duplication
• -usually affects the LONGEST nerves

Question 30

What kind of distribution is Diabetic Neuropathy?

Answer 30

–Sock and Glove numbness/tingling