A 28-year-old woman presents with ptosis, diplopia, and proximal muscle weakness that worsens with activity and improves with rest. Antibodies against the acetylcholine receptor are detected. Which mechanism best explains the muscle weakness in this condition?

• A Immune complex deposition at the neuromuscular junction
• B Mast cell degranulation causing muscle edema
• C Cytotoxic T cell destruction of muscle fibers
• D Antibody-mediated blockade and destruction of acetylcholine receptors ✓

Explanation

Myasthenia gravis is a Type II hypersensitivity reaction. Autoantibodies bind to acetylcholine receptors, blocking acetylcholine binding and causing complement-mediated destruction of the receptors. This reduces muscle depolarization. Immune complex deposition is Type III, and cytotoxic T cells are Type IV.

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.