Myasthenia Gravis Flashcards
Neuromuscular disorder caused by a decrease in the number of available acetylcholine receptors
Myasthenia Gravis
Acetylcholine is synthesized in the _______ nerve terminal and stored in________
motor, vesicles (quanta)
Acetylcholine combines with the binding sites on the _____ subunits of the acetylcholine receptors
alpha
Acetylcholine receptor opens and permits the entry of _______ cations which produces depolarization
sodium
(TRUE or FALSE) Depolarization happens on the end-plate region of the muscle fiber
TRUE
Acetylcholine is hydrolyzed by ________ which terminates muscle contraction
acetylcholinesterase
In myasthenia gravis, the postsynaptic folds are __________
flattened or simplified
______________ is the amount of ACh released per impulse that normally decreases on repeated activity
Presynaptic rundown
MG is an autoimmune disorder most commonly caused by ___________
anti-AChR antibodies
Muscles commonly chosen in muscle biopsy are ______, _______, and ________
deltoid, biceps, and quadriceps
(men, women) are frequently affected in myasthenia gravis
women
Protein in NMJ which is involved in AChR clustering with reduction of AChRs
muscle-specific kinase (MuSK)
Low-density protein that is important in clustering of AChRs which is present in 1-3% of MG patients
lipoprotein receptor-related protein 4 (LRP4)
Class of MG which manifests as any ocular muscle weakness while all other muscles groups are normal
Class I
Class of MG which is characterized by moderate weakness of muscles other than ocular muscles that involves mostly oropharyngeal, respiratory muscles or both
Class IIIb
Class IVa MG is characterized by severe muscles weakness other than ocular muscles that involves mostly _____, _______, or both
limb, axial muscles
Bulbar weakness is seen mainly in _____________ positive MG
MuSK-antibody
The pathogenic antibodies in MG are _________ and __________ dependent
IgG, T cell
Cardinal features of myasthenia gravis are ________ and ___________ of muscles
weakness, fatigability
Common initial complaints of MG patients (2)
diplopia and ptosis
(TRUE or FALSE) Limb weakness in MG is often proximal and may be symmetric
FALSE
_____________ occurs when ventilatory weakness requires respiratory assistance
Myasthenia crisis
Thymus is abnormal in ~75% of (AChR antibody positive, MuSK antibody positive, LRP4 antibody positive) myasthenia gravis
AChR antibody positive
(TRUE or FALSE) Ocular MG is when the weakness is restricted to EOMs for 3 years is more likely to become generalized
FALSE
A quick and easy diagnostic test for MG that can be done in the clinic or at the bedside of a hospitalized patient, which is due to less depletion of quanta of AChR in the cold and reduced activity of AChE at the NMJ
Ice-pack test
_________ occurs when there is a combination of presynaptic rundown and decreased efficiency of neuromuscular transmission
Myasthenic fatigue
___________ is an autoimmune disorder caused by antibodies that block ACh release by inhibiting a presynaptic calcium channel
Lambert-Eatan Myasthenic Syndrome
_______ is a protein derived from motor nerves that normally binds to LRP4 and important for normal clustering of AChRs at NMJ
Agrin
Antibodies directed against _______ receptors and ________ are associated in patients with thymoma and MG and neuromyotonia or Morvan syndrome
Netrin-1, Caspr2
(TRUE or FALSE) In electrodiagnostic testing, myasthenic patients have a rapid reduction of >10% in amplitude of the evoked responses
TRUE
Edrophonium is used to (treat/diagnose) MG because of its rapid onset (30s) and short duration (~5min) of its effect
diagnose
Positive result in Tensilon test is diagnostic for MG who have negative ______, ________________ , or ________.
antibody, electrodiagnostic test, ice-pack test
People with certain genetic markers called __________ are at risk of MG
HLA-B8, D3
__________ patients typically do not experience myasthenic crisis, but are generally difficult to treat than _________ MG
Anti-MuSk, Anti-AChR
__________ or _________ can cause exacerbation of weakness in myasthenic patients
Aminoglycoside antibiotics, procainamide
Initial dose of ____ of Edrophonium is given, and thye result is said to be positive if definitive improvement occurs
2mg IV
Common side effects of Edrophonium are nausea, diarrhea, salivation, fasciculation, syncope and bradycardia, so _______ is given when the symptoms of the side effects worsen
Atropine
A synthetic quaternary amine that binds reversibly to the active center of AChE to prevent the hydrolysis of ACh
Edrophonium
A synthetic quaternary amine that is a reversible AChE inhibitor that has greater effect on skeletal muscle and contraindications to patients with intestinal or urinary bladder obstruction
Neostigmine
An intermediate-acting cholinesterase inhibitor that has a duration of 3-6hrs and is used in the management of chronic myasthenia gravis
Pyridostigmine
Physostigmine is also called ________, a naturally occurring tertiary amine that acts as substrate for AChE
Eserine
Intermediate-acting cholinesterase inhibitors such as neostigmine, pyridostigmine and physostigmine are called _________
Carbamates
Muscle-like cells within the thymus
Myoid cells
Treatment with _________ and ____ may be used before thymectomy to maximize strength in weak patients
plasmapheresis, IVIg
It is the mechanical separation of plasma with blood cells that produces short-term reduction in AChR
plasmapheresis
Prednisone is converted to _________ and alters the gene expression by binding to glucocorticoid receptors in the body
Prednisolone
A csDMARD drug that inhibits the de novo synthesis of purine and inhibits the proliferation of lymphocytes
Mycophenolate Motefil
It suppresses inosinic acid synthesis, B-cell and T-cell function, Ig production and IL-2 secretion, through its major metabolite 6-thioguanine
Azathioprine
Calcineurin inhibitor that regulates gene transcription, inhibits IL-1 and IL-2 receptor productions, and macrophage-T cell interaction and T cell responsiveness
Cyclosporine
Rituximab binds to the ____ molecule on B lymphocytes
CD20
Chimeric monoclonal antibody that is more effective in MuSK antibody-positive MG
Rituximab
csDMARD that is converted to Phosphoramide mustard (active form) which cross-links DNA to prevent cell replication
Cyclophosphamide
Exacerbation of weakness sufficient to endanger life
Myasthenic crisis
Treatment for myasthenic crisis include (give at least 2, there are 5 answers)
Antibiotics, ventilatory assistance, pulmonary physiotherapy, plasmapheresis, IVIg
Weakness and fatigability of proximal or distal etemity muscles, EOMs and eyelids caused by genetic mutations
Non-autoimmune congenital myasthenia
Symptoms include ptosis of the eyelids, diplopia, depressed or absent reflexes, dry mouth and impotence
Lambert-Eaton Myasthenic Syndrome (LEMS)
LEMS is caused by autoantibodies directed against __________ calcium channels at the motor nerve terminals
P/Q-type
In older adults, LEMS is associated with malignancy, most commonly ______________________
small-cell lung cancer (SCLC)
Symptoms of Botulism (Give the 4 Ds)
Diplopia, Dysarthria, Dysphonia, Dysphagia
Most common cause of botulism
ingestion of improperly prepared food containing toxin
Historic name for myasthenia-like fatigue syndrome without organic basis
Neurasthenia
Muscle testing in neurasthenia reveals that it is a ___________ which is a characteristic of nonorganic disorder or tiredness or apathy
“give-away weakness”
Diplopia resembling in MG is due to an intracranial mass lesion that compresses nerves to the EOMs
Hyperthyroidism
Weakness of the EOMs which may be accompanied by weakness of the proximal muscles of the limb and is associated with mitochondrial conditions
Progressive external opthalmoplegia
Penicillamine induces the production of AChR antibodies
Drug-induced myasthenia
Neoplastic change also called ______ may produce enlargement of the thymus
thymoma
