1.4 Skeletal Muscle, NMJ, Soft Tissue Tumors Flashcards
how to differentiate dermatomyositis with polymyositis?
- Perimysial vs Endomysial inflammation
- dermatomyositis: perimysial (‘closer to skin, so dermato-‘)
dermatomyositis
- clinical findings (3)
- which is considered classic hallmark symptoms?
- “can’t comb hair, can’t climb stairs”–classic hallmark.
- proximal muscle weakness, distal later - heliotrope rash, malar rash
- Gottron papules (red papules on elbows, knuckles, knees)
dermatomyositis
- lab findings (4)
- blood and biopsy
- increased CK
- ANA (don’t mistake for lupus)
- anti-Jo-1 Ab (hallmark finding)
- perimysial inflammation, leads to perifascicular atrophy (biopsy)
How does dermatomyositis present similarly to lupus, and how to differentiate in labs?
-both have malar rash and + ANA
- do more tests:
- lupus has anti-dsDNA Ab
- dermatomyositis has anti-Jo-1 Ab
Duchenne’s muscular dystrophy (x-linked)
- mech/etiology
- clinical findings
- hallmark finding
- muscle turns into fat. muscle wasting
- defect in dystrophin gene (no dystrophin is produced), which anchors muscle to ECM.
- first presents as proximal muscle weakness at age 1, distal later
- Hallmark: Calf pseudohypertrophy–baby learning to walk has proximal muscle weakness so puts pressure on calf, which hypertrophies. Then, distal phase–calf turns into fat.
why does dystrophin get spontaneous mutations so often?
dystrophin is the biggest human gene.
Duchenne’s muscular dystrophy (x-linked)
-what is abnormal on labs?
-increased CK
how do duchenne’s muscular dystrophy kids die?
- Cardiac or respiratory failure.
- myocardium commonly involved
Becker’s muscular dystrophy
- less severe version of Duchenne’s
- mutated dystrophin, so reduced dystrophin is produced.
- as opposed to Duchenne’s, where dystophin is not produced.
Myasthenia gravis vs Lambert-Eaton syndrome
-how do symptoms differ?
- MG: weakness gets worse with repeated use (contraction uses up presynaptic Ach)
- LE: weakness gets better with repeated use (contraction increases Ca+ gradient into presynaptic neuron)
- LE: proximal muscles weak. eyes usu spared.
-Tx: anticholinersterases do not work for LE
Lambert-Eaton syndrome
- mech
- etiology
- symptoms
- Ab against Ca+ channels on presynaptic terminal in NMJ
- blocked Ca+ channels block Ach release
- arises as paraneoplastic syndrome, usu small cell carcinoma of lung
-proximal muscles weak, improves with use. Eyes usu spared.
what disorders are myasthenia gravis associated with?
- thymic hyperplasia
- thymoma
most common benign soft tissue tumor in adults
lipoma
most common malignant soft tissue tumor in adults
liposarcoma
most common malignant soft tissue tumor in children
rhabdomyosarcoma
