18.4 Skeletal muscles and Neuromuscular stuff Flashcards
What, generally, is dermatomyositis?
Idiopathic Inflammatory disorder of the skin and skeletal muscle
What is usually associated with dermatomyositis?
GI malignancies
What are the muscular features of dermatomyositis?
- Bilateral proximal muscle weakness
- Distal involvement later in dz course
What are the skin features of dermatomyositis?
- Rash of the upper eyelids (heliotrope rash)
- Red papules on the elbows, knuckles, and knees
Malar rash + bilateral proximal muscle weakness = ?
Dermatomyositis
What enzyme is classically elevated with dermatomyositis?
CK
What are the antibodies that are found with dermatomyositis?
ANA
Anti-Jo-1
What are the immune cells that cause the destruction in dermatomyositis? Where is the inflammation seen histologically?
CD4+ T cells
Perimysial inflammation
What is the treatment for dermatomyositis?
Corticosteroids
ANA +, malar rash, and Anti- Jo-1 = ?
Dermatomyositis
What is the CT layer that surrounds a single fascicle? Multiple?
Single = perimysium Multiple = Epimysium
(endomysium surrounds muscle fibers)
What, generally, is polymyositis? How does it compare to dermatomyositis?
Inflammatory disorder of the skeletal muscle that resembles dermatomyositis, but lacks skin involvement
What part of the muscles is inflamed with polymyositis? What are the immune cells that cause this?
Endomysial inflammation by CD8+ T cells
Match: (endomysial/ perimysial inflammation); (polymyositis/ dermatomyositis)
- Polymyositis = endomysial
- Dermatomyositis = perimysial
What is the inheritance pattern of muscular dystrophies? What is the genetic defect with this?
- XLR
- Deletions of dystrophin gene (for for Duchenne)
What is the pathological process that characterizes muscular dystrophy?
Replacement of skeletal muscles by adipose tissue
What is the function of dystrophin protein?
Anchors muscle cytoskeleton to the extracellular matrix
Why is muscular dystrophy often a spontaneous, as opposed to an inherited one?
Dystrophin gene is one of the largest in the human genome, and thus is more susceptible to damage
What is the genetic defect in Becker’s vs Duchenne’s muscular dystrophy?
Beckers = mutation Duchennes = deletion
How do kids with Duchenne muscular dystrophy usually present?
Proximal muscle weakness before 1 year of age
What is the classic feature of Duchenne muscular dystrophy?
Calf pseudohypertrophy (2/2 fat deposition)
What is the enzyme that is elevated with Duchenne muscular dystrophy?
CK
What usually causes death with Duchenne muscular dystrophy?
Cardiac or respiratory failure
What part of the heart is involved with Duchenne muscular dystrophy?
Myocardium
Why is MG characterized by fatigable muscles?
Each time contraction occurs, less ACh is able to be release and compete with anti-nicotinic abs
Are the antibodies with MG competitive or noncompetitive for ACh receptors?
Competitive
Which gender is more commonly affected with MG?
Women
What part of the body is classically affected with MG?
Eyes–ptosis and diplopia
What is MG classically associated with and can be seen on CXR?
Thymic hyperplasia or thymoma
What malignancy is classically associated with Lambert-Eaton syndrome?
small cell lung cancer
Why does muscle strength improve with Eaton-Lambert syndrome?
Keep trying to force Ca in competes with antibody
True or false: the eyes are classically affected with Eaton-Lambert syndrome
False– spared. MG is classically affected
How do you differentiate MG and Eaton-Lambert syndrome clinically, besides history?
Anticholinesterase agents do not improve symptoms
What is the most common benign soft tissue tumor in adults?
Lipomas
What is the most common malignant soft tissue tumor in adults?
Liposarcomas
What is the characteristic cell of liposarcomas?
Lipoblasts
What is cardiac rhabdomyomas usually seen with?
Tuberous sclerosis
What, generally, is a rhabdomyoma?
Benign tumor of skeletal muscle
What, generally, is a rhabdomyosarcoma?
Malignant tumor of skeletal muscle
What is the characteristic cell of rhabdomyosarcomas?
Rhabdomyoblast
What is the most common site of a rhabdomyosarcoma? What is the classic presentation in young girls?
Head and neck most common
Vagina in young girls
What is the most common malignant soft tissue tumor in children?
Rhabdomyosarcoma
What is the stain that highlights rhabdomyosarcomas?
Desmin
Young girl with a grape-like mass protruding from the vagina = ?
Rhabdomyosarcoma
