Pathoma - MSK - Skeletal muscle, NMJ, Soft tissue tumors Flashcards
What is dermatomyositis
Inflammatory disorder of the skin and skeletal muscle
Clinical presentation of dermatomyositis
Bilateral proximal muscle weakness
Rash of upper eyelids (heliotrope rash) and malar rash
Gottron papules - red papules on elbows, knuckles, and knees
What are the inflammatory cells and the location of inflammation in dermatomyositis?
Perimysial inflammation (CD4+ T cells)
Think: include muscle and skin so inflammation must be in periphery
What are the inflammatory cells and location of inflammation in polymyositis
Polymyositis - progressive symmetric muscle weakness (similar to dermatomyositis but without skin involvment)
Inflammation of the endomysium (CD8+ T cells)
What is the basic premise behind muscular dystrophy
Degenerative disorder characterized by muscle wasting and replacement of skeletal muscle by adipose tissue
What is the normal function of dystrophin gene
Dystrophin helps to anchor muscle fiber
Connects the intracellular cytoskeleton (actin) to transmembrane proteins which are conected to the extracellular matrix
What is the gene defect in Duchenne muscular dystrophy
Deletion of dystrophin (due to frameshift or nonsense mutation)
What are common clinical features and cause of death in Duchenne muscular dystrophy
Proximal weakness - onset before 5 y/o
Pseudohypertrophy of calf due to fatty replacement of muscle
Death usually from dilated cardiomyopathy
What is the gene defect in Becker muscular dystrophy
Mutation of dystrophin gene
Milder form of Duchenne
Onset in adolescence or early adulthood
What is the pathophysiology of myasthenia gravis
Autoantibody against post-synaptic ACh receptor
Clinical features of myasthenia gravis
Ptosis (drooping eyelid), diplopia (double-visin), weakness
Worsens with muscle use
Malignancies associated with myasthenia gravis
Thymoma, thymic hyperplasia
What is the pathophysiology of Lambert-Eaton myasthenic syndrome
Autoantibodies against pre-synaptic calcium channels, leading to decreased ACh release
Clinical features of Lambert-Eaton
Proximal muscle weakness that improves with use
Eyes are usually spared
Autonomic symptoms (dry mouth, impotence)
Malignancies associated with Lambert-Eaton
Small cell lung cancer
Effects of acetylcholinesterase inhbitors on Myasthenia gravis vs. Lambert Eaton
Will improve symptoms of myasthenia gravis
No/minimal improvement of Lambert-Eaton
What is a lipoma
Benign tumor of adipose tissue
Most common benign soft tissue tumor in adults
What is a liposarcoma
Malignant tumor of adipose tissue
Most common malignant soft tissue tumor in adults
Lipoblast is the characteristic cell
What is a rhabdomyoma
Benign tumor of skeletal muscle
Cardiac rhabdomyoma is associated with tuberous sclerosis
What is a rhabdomyosarcoma
Malignant tumor of skeletal muscle
Rhabdomyoblast is the characteristic cell (desmin positive)
Common sites of rhabdomyosarcoma
Most common site is head and neck
Vagina is the classic site in young girls
