Skeletal Muscle Disorders (inflammatory, congenital) Flashcards
(26 cards)
Presnetation of myotonic muscular dystrophy
Motor:
- Muscle wasting/ weakness
- Myotonia (hypercontractility of muscle)
Extra-muscular manifestations: CTG
- C: Cataracts
- T: Toupee (early balding in men)
- G: gonadal atrophy (testicular atrophy)
Anti-jo-1 antibodies are antibodies against what? What disease are they found in
Aminoacyl-tRNA-synthetase antibodies. Found in dermatomyositis + polymyositis
Becker muscular dystrophy etiology
Mutation in dystrophin gene–> partially functional dystrophin protein
Etiology of X-linked muscular dystrophy
X-linked mutation in dystrophin protein (anchors intracellular cytoskeleton of muscles to ECM)
Characterized by progressive muscle damage w/ replacement of skeletal muscle by adipose tissue
X-linked muscular dystrophy
Most common adult onset muscular dystrophy
Myotonic dystrophy
Pathophysiology of dermatomyositis
Autoantibodies against endothelial cells, activate complement and destroy capillaries leading to infarcts –> dropout of muscle cells close to affected capillaries
Difference between biopsy of dermatomyositis + polymyositis
Dermatomyositis- CD4+ infiltrates; occurs in perimysium w/ perifascicular atrophy around edges
Polymyositis- CD8+ infiltrates; occurs in endomysium (all around muscle cells)
Extra-muscular features of Duchenne muscular dystrophy
1) Cardiac dysfunction - dilated cardiomyopathies + arrhyhtmias
2) Death results from cardiac or respiratory failure
Presentation of Becker muscular dystrophy
Similar to Duchenne but later age of onset and milder sx
Motor presentation of Dermatomyositis; which muscle group usually spared?
Motor:
1) Proximal, symmetrical weakness/ myalgia involving large muscles groups (climbing stairs, combing hair, raising arms above head, etc.)
2) Neck extensor muscles- “head drop”
* ocular muscles are spared (vs. myasthenia gravis)
biopsy of inclusion body myositis
Muscle cytoplasmic inclusion proteins associated w/ neurodegenerative disease
Associated w/ malginancy (esp. gastric carinoma)
Dermatomyositis
Cutaneous findings of dermatomyositis
1) Gottron papules- raised, scaly, red/violaceous rash on elbow, knuckles, knees
2) Heliotrope rash- rash of upper eyelids
3) Malar rash
4) Mechanic’s hands- cracking of finger pad skin
5) V-neck or shawl pattern rash- lesions in upper chest, back, base of neck
Motor signs + sx of Duchenne msucular dystrophy
1) Clumsiness, difficult climbing, running, jumping
2) Waddling gait w/ Gowers sign
3) Delayed developmental milestones (speaking, sitting, waling)
4) calf pseudohypertrophy
Pts are wheelchair bound by 12
Main difference in presentation between dermatomyositis + polymyositis
Dermatomyositis presents w/ a variety of skin findings; polymyositis does not
Etiology of Duchenne muscular dsytophy
X-linked DELETION of dystrophin gene- absence of protein
MHC-1 expression on muscle cells occurs in which disease
Polymyositis
When do symptoms of X-linked muscular dystrophy arise?
Between childhood/ adulthood (most commonly around 2-7); does NOT present in infancy
Biopsy of polymyositis
CD8+ lymphocyte infiltration in endomysial distribution- inflammatory cells all around muscle cells
Biopsy of Dermatomyositis
Perimysial inflammation w perifascicular atrophy; most damage around the edges
CD4+ infiltrate
Biopsy of muscle in Duchenne muscular dystrophy
Absence of dystrophin (staining)
Fatty replacement of muscle tissue
Types of X-linked muscular dystrophy
1) Duchenne Muscular dystrophy
2) Becker muscular dystrophy
Lab findings of dermatomyositis + polymyositis
1) High creatine kinase
2) Anti-Jo-1 antibodies (aminoacyl-tRNA-synthetase antibodies)
3) Anti-Mi-2 antibodies (nuclear helicase autoantibody)
4) ANA
