Clinical meaning
Myasthenia gravis is an autoimmune disorder in which IgG autoantibodies bind to nicotinic acetylcholine receptors (AChRs) on the postsynaptic membrane of the neuromuscular junction. This binding activates complement, destroys receptors, and reduces the number of functional AChRs. As a result, acetylcholine released from motor nerve terminals is insufficient to depolarize the postsynaptic membrane and generate a muscle action potential. The weakness is characteristically fatigable: repeated use of a muscle group depletes available ACh and worsens weakness, while rest allows replenishment. The thymus gland is implicated in 85% of patients (hyperplasia or thymoma). The nurse manages medication timing, performs serial respiratory and neurological assessments, distinguishes between myasthenic and cholinergic crises, implements aspiration precautions, and coordinates multidisciplinary care.
Exam relevance
Risk factors: - Bimodal age distribution: women 20-40 years, men 60-80 years - Thymic abnormalities: thymic hyperplasia (65%), thymoma (10-15%) - Other autoimmune conditions (thyroiditis, rheumatoid arthritis, SLE) - Family history of autoimmune disease - HLA-B8 and HLA-DR3 genetic associations - Exacerbation triggers: infection, stress, surgery, pregnancy, temperature extremes - Medications that worsen MG: aminoglycosides, fluoroquinolones, macrolides, beta-blockers, magnesium, D-penicillamine