Msck - disease of the Skeletal muscle

Question 1

immunohesitochemistry used to stain Monocytes

Answer 1

NADH-HR

Question 2

Myosin ATP-ase; pH: 4.3 Vs Myosin ATP-ase; pH: 9.4 for Type I/II muscle fibers

Answer 2

Question 3

Type I vs Type IIA vs Type IIB muscle fibers on Histology

Answer 3

Question 4

Denervation Atrophy invloves ——– fibers

Answer 4

Type I and Type II fibers

Question 5

Disuse Atrophy involves —— fibers

Answer 5

Type II fibers only

* unlike Denervation atrophy which involved type I and II

Question 6

Causes of Disuse Atrophy

Answer 6

Prolonged immobilisation
(not using muscles enough so –> muscles break down and decrease in size)

Question 7

Histology of Denervation Atrophy:
▪ Involvement of ——– fibres
▪ Small and ———- as well as ———-
▪ Fibre ———–, after re-innervation

Answer 7

▪ Involvement of both type I and type II fibres
▪ Small and angular fibers as well as target fibres
▪ Fibre type grouping, after re-innervation

Question 8

Histopatho:
▪ Involvement of both type I and type II fibres
▪ Small and angular fibers as well as target fibres
▪ Fibre Type grouping, after re-innervation

features of?

Answer 8

Denervation Atrophy

Question 9

what do you obsever , what condition causes this?

Answer 9

Target fibers caused by Denervation Atrophy

* traget fibers are normally found on type I fibers

Question 10

Histology of Disuse Atrophy:
——— of type II fibers

Answer 10

Angular Atrophy of type II fibers

Question 11

Muscular Dystrophies examples

Answer 11

1) Duchenne Muscular Dystrophy
2) Becker Muscular Dystrophy

Question 12

CF of muscular dystrophies

Answer 12

Progressive muscle wasting and weakness due to degenration of Skeletal muscles

Question 13

Lab findings of Muscular Dystrophies

Answer 13

Increased serum Creatine kinase (CK)

Question 14

cause of Duchenne muscular dystrophy

Answer 14

X-linked disroder –> De novo mutations of the Dystrophin gene (Deficiency of Dystrophyin)

* X-linked recessive

Question 15

Epi of Duchenne muscular dystrophy

Answer 15

• Male children
• most common/sever muscular dystrophy

Question 16

Duchenne muscular dystrophy

Microscopic findings:
- Random variation in muscle fibre ——–
- ———— perimysial and endomysial fibrosis
- Basophilic regenerating myotubes
- Amorphous pink cytoplasm in —————
- Many, irregularly scattered ———–

Answer 16

• Random variation in muscle fibre size
• moderate perimysial and endomysial fibrosis
• Basophilic regenerating myotubes
• Amorphous pink cytoplasm in necrotic msucle
• Many, irregularly scattered hyaline fibers

Question 16

Microscopic features:
- Random variation in muscle fibre size
- moderate perimysial and endomysial fibrosis
- Basophilic regenerating myotubes
- Amorphous pink cytoplasm in necrotic msucle
- Many, irregularly scattered hyaline fibers

features of?

Answer 16

Duchenne muscular dystrophy

Question 17

Lab findings of Duchenne Muscular dystrophy

Answer 17

Increased serum CK

Question 18

What do you observe + found in what condition?

Answer 18

Many, irregulary scattered Hyaline fibers –> found in Duchenne muscular dystrophy

Question 19

CM of Duchenne muscular dystrophy

Answer 19

1) Proximal muscle weakness of the extremities –> immobolization, wasting, muscle contracture (death due to pneumonia)
2)Enalrgement of the calves (Compensatory hypertrophy of distal sites)

Question 20

Cause of Becker Muscular dystrophy

Answer 20

Abnormality in Dystrophin caused by segmental deletions within the gene

Question 21

CM of Becker muscular dystrophy

Answer 21

similar to Duchenne but less severe

Question 22

Becker muscular dystrophy

Microscopic features:
- —— to —— Endomysial and Perimysial fibrosis
- ——- Hyaline fibers
- Variation in muscle fiber size

Answer 22

Microscopic features:
- mild to light Endomysial and Perimysial fibrosis
- No Hyaline fibers
- Variation in muscle fiber size

Question 23

Microscopic features:
- mild to light Endomysial and Perimysial fibrosis
- No Hyaline fibers
- Variation in muscle fiber size

features of?

Answer 23

Becker Muscular dystrophy

Question 24

Cause of Facio-scapulo-humoral muscular dystrophy

Answer 24

Autosomal Dominant Disorder

Question 25

CM of Facio-scapulo-humoral muscular dystrophy

Answer 25

- Slowly progressive, non-disabling course - Sequential involvement of muscles of the **face, scapular area and humerus**

Question 26

Facio-Scapulo-Humoral muscular dystrophy involves?

Answer 26

Sequential involvement of muscles of the **face, scapular area and humerus**

Question 27

Microscopic features: - **severely** atrophic fibers - Marked variation of musclel fiber size - **Grossly hypertrophied fibers** - **Prominant intertitial fibrosis** features of?

Answer 27

Facio-Scapulo-Humorla muscular Dystrophy

Question 28

cause of Limb Gridle Dystrophy

Answer 28

Autosomal recessive Disorder

Question 29

what muscles are affected by Limb Gridle Dystrophy

Answer 29

proximal muscles of the shoulder, pelvic girdle (bony pelvis) or both

Question 30

Microscopic features: - Variation in muscle fiber size - Greatly Hypertrophied fibers - **Endomysial fibrosis** - Atrophic fibers features of?

Answer 30

Limb Gridle dystrophy

Question 31

Cause of Myotonic Dystrophy

Answer 31

AD inheritance --> Trinucleotide repeat **(CTG)** disorder (repeats in Myotonin protein kinase gene)

Question 32

Myotonic dystrophy is an AD disorder --> Trinucleotide repeat **-----** (repeats in **------------** gene)

Answer 32

AD inheritance --> Trinucleotide repeat **(CTG)** disorder (repeats in **Myotonin protein kinase** gene)

Question 33

CF of Myotonic Dystrophy

Answer 33

1) **Muscle weakness w/ Myotonia** (inability to relax muscles once contracted) 2) Cataracts 3) Testricular Atrophy 4) Baldness (males)

Question 34

# Myotonic Dystrophy Microscopic features: Many of the small fibres with a **------------**

Answer 34

Many of the small fibres with a **central nucleus**

Question 35

**Congenital Myopathies** are disorders characterised by **-----------------** (marked hypotonia at birth)

Answer 35

characterised by **floppy infant syndrome** (marked hypotonia at birth)

Question 36

Lab findings in Congenital Myopathies

Answer 36

Normla serum CK

Question 37

The 3 types of Congenital Myopathies

Answer 37

➢ Central Core Disease ➢ Nemaline Myopathy ➢ Mitochondrial Myopathies

Question 38

# * Congenital myopathy Patho of Central core disease: Loss of **------------** and other organelles in the **----------** portion of type **----** muscle fibres

Answer 38

Loss of **mitochondria** and other organelles in the **central** portion of type **I** muscle fibres

Question 39

CM of central core disease

Answer 39

Muscle weakness and **hypotonia** (Decreased muscle tone)

Question 40

Microscopic findings: features of?

Answer 40

Central core disease

Question 41

Microscopic findings: Tangles of small rod-shaped granules **("Rod bodies")**, predominantly in type I fibres feature of?

Answer 41

Nemaline Myopathy

Question 42

Distinctive micro featurs of Nemaline Myopathy

Answer 42

**"Rod bodies"** in type I fibers

Question 43

CM of Nemaline Myopathy

Answer 43

Variable clinical presentation; from mild, non- progressive disease to severe weakness → Death from respiratory failure

Question 44

Cause of Mitochondrial Myopathies

Answer 44

▪ **Non-Mendelian inheritance** ▪ **Maternally transmitted** mitochondrial DNA abnormalities

Question 45

Microscopic features: ▪ **"Ragged red"** appearance of muscle fibres ▪ Various mitochondrial enzyme or co-enzyme defects (detected by immuno-histochemistry -**NADH-TR**) features of?

Answer 45

Mitochondrial Myopathies

Question 46

Distinctive micro features found in Mitochondrial Myopathies

Answer 46

**"Ragged Red"** appearance of muscle fibers