A 45-year-old woman presents with progressive proximal muscle weakness, ptosis, and diplopia that worsen with activity and improve with rest. Anti-acetylcholine receptor antibodies are positive. The antibody-mediated destruction of acetylcholine receptors at the neuromuscular junction, with complement-mediated damage to the postsynaptic membrane, is characteristic of which hypersensitivity type?
- A Type I (anaphylactic)
- B Type III (immune complex)
- C Type II (cytotoxic) ✓
- D Type IV (delayed-type)
Correct answer: C. Type II (cytotoxic)
Explanation
Myasthenia gravis is a classic Type II hypersensitivity reaction where IgG autoantibodies bind acetylcholine receptors, leading to complement-mediated destruction of the postsynaptic membrane. Type I involves IgE and mast cells. Type III involves immune complex deposition. Type IV is T-cell mediated and delayed. The antibody-mediated cytotoxicity against cell-surface receptors defines Type II.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.