Pathoma - MSK - Skeletal muscle, NMJ, Soft tissue tumors

Question 1

What is dermatomyositis

Answer 1

Inflammatory disorder of the skin and skeletal muscle

Question 2

Clinical presentation of dermatomyositis

Answer 2

Bilateral proximal muscle weakness

Rash of upper eyelids (heliotrope rash) and malar rash

Gottron papules - red papules on elbows, knuckles, and knees

Question 3

What are the inflammatory cells and the location of inflammation in dermatomyositis?

Answer 3

Perimysial inflammation (CD4+ T cells)

Think: include muscle and skin so inflammation must be in periphery

Question 4

What are the inflammatory cells and location of inflammation in polymyositis

Answer 4

Polymyositis - progressive symmetric muscle weakness (similar to dermatomyositis but without skin involvment)

Inflammation of the endomysium (CD8+ T cells)

Question 5

What is the basic premise behind muscular dystrophy

Answer 5

Degenerative disorder characterized by muscle wasting and replacement of skeletal muscle by adipose tissue

Question 6

What is the normal function of dystrophin gene

Answer 6

Dystrophin helps to anchor muscle fiber

Connects the intracellular cytoskeleton (actin) to transmembrane proteins which are conected to the extracellular matrix

Question 7

What is the gene defect in Duchenne muscular dystrophy

Answer 7

Deletion of dystrophin (due to frameshift or nonsense mutation)

Question 8

What are common clinical features and cause of death in Duchenne muscular dystrophy

Answer 8

Proximal weakness - onset before 5 y/o

Pseudohypertrophy of calf due to fatty replacement of muscle

Death usually from dilated cardiomyopathy

Question 9

What is the gene defect in Becker muscular dystrophy

Answer 9

Mutation of dystrophin gene

Milder form of Duchenne

Onset in adolescence or early adulthood

Question 10

What is the pathophysiology of myasthenia gravis

Answer 10

Autoantibody against post-synaptic ACh receptor

Question 11

Clinical features of myasthenia gravis

Answer 11

Ptosis (drooping eyelid), diplopia (double-visin), weakness

Worsens with muscle use

Question 12

Malignancies associated with myasthenia gravis

Answer 12

Thymoma, thymic hyperplasia

Question 13

What is the pathophysiology of Lambert-Eaton myasthenic syndrome

Answer 13

Autoantibodies against pre-synaptic calcium channels, leading to decreased ACh release

Question 14

Clinical features of Lambert-Eaton

Answer 14

Proximal muscle weakness that improves with use

Eyes are usually spared

Autonomic symptoms (dry mouth, impotence)

Question 15

Malignancies associated with Lambert-Eaton

Answer 15

Small cell lung cancer

Question 16

Effects of acetylcholinesterase inhbitors on Myasthenia gravis vs. Lambert Eaton

Answer 16

Will improve symptoms of myasthenia gravis

No/minimal improvement of Lambert-Eaton

Question 17

What is a lipoma

Answer 17

Benign tumor of adipose tissue

Most common benign soft tissue tumor in adults

Question 18

What is a liposarcoma

Answer 18

Malignant tumor of adipose tissue

Most common malignant soft tissue tumor in adults

Lipoblast is the characteristic cell

Question 19

What is a rhabdomyoma

Answer 19

Benign tumor of skeletal muscle

Cardiac rhabdomyoma is associated with tuberous sclerosis

Question 20

What is a rhabdomyosarcoma

Answer 20

Malignant tumor of skeletal muscle

Rhabdomyoblast is the characteristic cell (desmin positive)

Question 21

Common sites of rhabdomyosarcoma

Answer 21

Most common site is head and neck

Vagina is the classic site in young girls