MSK immunology Flashcards
what is myasthenia gravis?
Autoimmune neuromuscular disorder
Severe muscle weakness and severe fatigue
what is the pathology behind MG?
Auto-reactive antibodies (auto-IgG) bind with acetylcholine receptors on muscle cells
diseases assoc with MG
SLE, rheumatoid and thyrotoxicosis
cause of MG in 10%
thymus tumour
cause of MG in 90%
unknown
genetic assoc of MG
HLA associations
appearance of MG
pregnancy
post partum
certain anaesthetic agents
which body parts are usually affected first
eyes face mouth throat neck
when is it life threatening
when all muscle are weak -> impairment of respiration
most important factor in recovery
rest
pathophysiology 1
CD4+ T cells are activated by unfolded AChR subunits expressed by thymic epithelial cells
pathophysiology 2
Effector T cells stimulate auto-reactive B cells resulting in the production of anti-AChR IgG antibodies
pathophysiology 3
Thymic myoid cells are attacked by these antibodies and release AChR-IgG immune complexes
pathophysiology 4
These immune complexes activate other antigen presenting cells increasing the response
result of pathophysiology
AChR antibodies block binding of endogenous ACh ligands to these receptors, leading to defects in nerve impulse transmission at the skeletal muscle NMJ
final result of MG
Antibody-bound receptors are internalised and degraded
AChR antibodies bind complement, leading to destruction of the muscle endplate (type II hypersensitivity)
lab test to diagnose MG
presence of anti-AChR IgG in serum
repetitive nerve stimulation to diagnose MG
gradually reducing responses indicates NMJ dysfunction
treatment to increase neurotransmission
Anti-cholinesterase agents eg pyridostigmine
surgery for MG that may be indicated in the case of a tumour
Thymectomy
treatment to reduce autoimmune reactions
Immunosuppressive drugs
Corticosteroids
