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DT 1 Test 1 > Skeletal Muscle > Flashcards

Skeletal Muscle Flashcards

1
Q

What is the pathology of spinal muscular atrophy?

A

Progressive destruction of anterior horn cells and cranial nerve motor neurons

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2
Q

What is the mutation and inheritance that causes spinal muscular atrophy?

A

Autosomal recessive

Survival Motor Neuron 1 (SMN1)

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3
Q

What is the cause of Duchenne Muscular Dystrophy?

A

Dystrophin protein defect from abnormal gene

Most common type of MD

X-linked

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4
Q

What is the clinical presentation of DMD?

A

Normal at birth, followed by delayed walking and clumsiness

Pseudohypertrophy of the calves

Impaired cognition

Death occurs from respiratory failure, cardiac decompensation, or lung infection

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5
Q

What is Becker Muscular Dystrophy?

A

Defect in dystrophin quality/quantity of protein

Less common, less severe, later onset than DMD

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6
Q

How does limb girdle muscular dystrophy present?

A

Begin to walk with a waddling gait because of weak hip and leg muscles

Trouble getting out of chairs or climbing stairs

Many types related to dystrophin glycoprotein complex

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7
Q

What is facioscapulohumeral MD?

A

Facial weakness and wasting of the upper arm and shoulder muscles

Winged scapula

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8
Q

What is the triad of Emery’Dreifuss MD?

A

early on humeroperoneal weakness

Prominent contractures, especially in the elbows and ankles

Cardiomyopathy

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9
Q

What is the cause of myotonic dystrophy?

A

Autosomal dominant of expansion mutations in Dystrophila myotonia-protein kinase (DMPK)

Displays anticipation: onset at a younger age in succeeding generations

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10
Q

How does myotonic dystrophy present?

A

Stiffness and difficulty releasing grip

Onset in childhood

Abnormal gait, weakness of intrinsic hand and wrist extension

Facial muscle atrophy and ptosis

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11
Q

What is the most common channelopathy?

A

Hypokalemic periodic paralysis

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12
Q

What is hypokalemic periodic paralysis?

A

Most common is Ca channel mutations

Patient suffers attacckes of flaccid weakness provoked by carb meals, exercise, heat, cold, stress, meds

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13
Q

What is malignant hyperpyrexia?

A

Sudden hypermetabolic state with tachypnea and general muscle contraction

Triggered by anesthesia: Halogen containing gases or succinycholine

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14
Q

What is the cause and treatment of malignant hyperpyrexia?

A

Ryanodine receptor RyR1 mutation

Release of Ca from SR causes ATP depletion and anaerobic metabolism

Causes hyperthermia, Rhabdomyolysis, Hyperkalemia, Renal failure

Treatment: Dantrolene

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15
Q

What is Central core disease?

A

Autosomal dominant hypotonic myopathy caused by RYR1 gene defect

Risk for malginant hyperthermia

Centrally light area in type 1 fibers seen on microscopic examination

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16
Q

What is Nemaline myopathy?

A

Nonprogressive hypotonia, weakness that involve sproximal limb muscle

Causes developmental delays in kids

17
Q

What is centronuclear myopathy?

A

Myopathy characterized by central nuclei usually confined to type 1 fibers

18
Q

What are lipid myopathies caused by?

A

Defects in carnitine transport system or mitochondrial dehydrogenase enzyme system that results in the accumulation of lipid in myocytes

19
Q

What are mitochondrial myopathies and what is found on microscopic examination?

A

Oxidative phosphorylation diseases caused by defects in mtDNA or nuclear DNA

Ragged red fibers from aggregated mitochondria and mitchondria “parking lot” paracrystalline inclusions

20
Q

What is dermatomyositis?

A

Skin rash precedes or bigeins with myositis

Causes scaling erythematous eruption or dusky red patches over knuckles, elbows, knees (Grotten lesions)

Slow and symmetrical muscle weakness with or without myalgias

21
Q

What additional symptoms occur in Juvenile dermatomyositis?

A

GI vasculopathy leads to ulceration, hemorrhage and perforation

22
Q

What is the pathology of dermatomyositis?

A

Microvasculature attacked by antibodies and compliment creating ischemia

Perifascicular atrophy

Inflammation in perimysial connective tissue NOT muscle

Mediated by CD4 T cells and B cells

23
Q

What is the pathology of Polymyositis?

A

Autoantibodies against tRNA synthetases

Can be +/- ANA positive

Cytotoxic CD8+ T cells in endomysium destroy muscle

24
Q

How does Polymyositis present?

A

Systemic inflammatory myopathy

Muscle weakness +/-myalgias

Lung disease, vasculitis, myocarditis

25
Q

What is the pathology of inclusion body myositis?

A

Intracellular depsoits of B-amyloid protein, B-pleated sheet fibrils, Hyperphosphorylated Tau protein

CD8 T cells

26
Q

How does inclusion body myositis present?

A

> 50 years begins insidiously

Distal muscles, quads, wrist and finger flexors

May be asymmetric

27
Q

What is thyrotoxic myopathy?

A

Acute or chronic proximal muscle weakness tha tmay precede signs of thyroid dysfunction

Exophthalmic ophthalmoplegia - protrusion of the eyeballs and diplopia due to orbital edema and contracture of ocular muscles

28
Q

How does hypothyroidism myopathy present?

A

Cramping/aching muscle; slow movement

Slow reflexes

Proximal weakness e.g. posterior neck

Elevated CK

Fiber atrophy

29
Q

What is ethanol myopathy?

A

Acute rhabdomyolysis after a drinking binge

Painful, myoglobinuria can lead to renal failure

30
Q

What drugs can induce myopathy?

A

Steroid

Chlororquine

Statins

31
Q

What is ICU myopathy?

A

Myosin deficient myopathy

Associated with corticosteroid therapy

Degraded myosin thick filaments

32
Q

What is the pathology of Myasthenia gravis?

A

Neuromuscular junction disease caused by an immune-mediated loss of acetylcholine receptors

33
Q

How does myasthenia gravis present?

A

Often begins with extraocular muscle weakness - drooping eyelids, diplopia

May present with generalized weakness that is variable from minute-to-minute

34
Q

What is the treatment for MG?

A

Thymectomy

Acetylcholinesterase

Prednisone

Plasmapherises

35
Q

What is Lambert-Eaton Myasthenic Syndrome?

A

Neuromuscular junction disorder caused by antibodies that inhibit presynaptic calcium channel and block acetylcholine release

Usually paraneoplastic from small cell carcinoma

Enhanced neurotransmission with repetitive stimulation

DT 1 Test 1 (18 decks)

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