Which autoimmune disorder causes fluctuating weakness and has no cure?

• A. Multiple sclerosis
• B. Myasthenia gravis
• C. Lupus
• D. Rheumatoid arthritis

Answer: (B)

Fluctuating, fatigable weakness is most characteristic of myasthenia gravis, an autoimmune attack on the neuromuscular junction. In this condition, antibodies target the postsynaptic acetylcholine receptors (or related proteins), so each use of a muscle is less able to generate a strong contraction. The result is weakness that worsens with activity and improves with rest, a hallmark pattern that helps distinguish it from other autoimmune diseases. There is no cure, but symptoms can be managed with treatments that improve neuromuscular transmission and suppress the immune response, such as acetylcholinesterase inhibitors, immunosuppressants, plasmapheresis or IVIG, and thymectomy in some cases. Other autoimmune diseases may involve weakness or systemic symptoms, but they don’t characteristically produce the same fatigable, activity-related weakness pattern seen in myasthenia gravis.