Inflammatory and Inherited Diseases of Skeletal Muscle

Question 1

Idiopathic Inflammatory Myopathy

Answer 1

Triad of findings including 1. Muscle Weakness 2. evidence of muscle inflammation/EMG findings 3. Elevated CK or other muscle-derived proteins

Question 2

Three Most common Idiopathic Inflammatory Disorders

Answer 2

1. Dermatomyositis
2. Polymyositis
3. Inclusion Body Myositis

Question 3

Dermatomyositis

Muscular presentation as well as histopathological findings

Answer 3

Mostly affects adults presenting with proximal, symmetrical muscle weakness (head drop and dysphagia as well)
OCULAR MUSCLES SPARED
Autoantibodies against Mi2 (specific to DM) and Jo1(DM and PM)
Associated with malignancy (annual workup for cancer for 3 years)
CD4+ T Cells seen in perimysium as well as perivascular atrophy

Question 4

Cutaneous presentation of Dermatomyositis

Answer 4

Gottron Papules
Heliotrope rash
V-neck or Shawl PAttern Rash
Mechanic's Hands
(also associated with Interstitial Lung Disease)

Question 5

Polymyositis keys and histopathologic features

Answer 5

RARELY a sole problem
Skin Manifestations not present (Only in DM)
CD8+ T Cells in the endomysium

Question 6

Inclusion Body Myositis

Answer 6

Affects men older than 65
no autoantibodies
CD8+ T cells in the endomysium (like PM)
Abnormal cytoplasmic inclusions containing neurodegenerative proteins

Question 7

Duchenne Muscular Dystrophy

Presentation and muscular symptoms

Other features

Answer 7

Complete lack of the dystrophin protein.
Most severe form of the X-linked MD’s
Muscle weakness that usually presetns between ages 2-7 and starts proximally
Calf-pseudo hypertrophy is seen
Delayed developmental milestones like speaking or walking
Wheelchair bound by age 12
Cardiomyopathy, short life expectancy, mild cognitive impairment

Question 8

Gower’s Sign

Answer 8

Getting up like a bear crawl and pushing on your knees to help you stand up (Seen in DMD/BMD)

Question 9

Becker Muscular dystrophy

Answer 9

Mutated form of Dystrophin ( as opposed to total lack of protein in DMD)
Later age of onset compared to DMD
Milder symptoms compared to DMD

Question 10

Myotonic Dystrophy, Type 1

Answer 10

Most common cause of adult onset muscular dystrophy.
Present between 15-40
Autosomal Dominant
Expansion of CTG in 3’ untranslated region of DMPK Gene
See adult onset myotonia, type 2 diabetes, and cardiomyopathy
FULL MUTATION= Greater than 50 CTG Repeats

Question 11

Genetic Anticipation

Answer 11

Seen in TNR disorders where the further down the generations the earlier the onset and the worse the symptoms.