Chronic auto immune disorder affecting neuro muscular junction leading to fatigue, weakening and paralysis of skeletal muscle is called as :

The correct option is Myasthenia gravis.

Step-by-step Explanation:
1. Understanding Myasthenia Gravis: Myasthenia gravis is a chronic autoimmune neuromuscular disorder. In autoimmune diseases, the immune system mistakenly attacks the body's own healthy tissues. Specifically, in myasthenia gravis, antibodies destroy, block, or alter the receptors for acetylcholine (a neurotransmitter) at the neuromuscular junction. This prevents nerve impulses from triggering muscle contractions, leading to progressive muscle weakness, fatigue, and potential paralysis of voluntary (skeletal) muscles.
2. Comparing with other options:
- Arthritis: This is a general term for inflammatory or degenerative conditions affecting the joints, leading to pain and stiffness, not a disorder of the neuromuscular junction.
- Muscular dystrophy: This is a group of genetic diseases characterized by progressive weakness and degeneration of skeletal muscles due to mutations in genes responsible for muscle structure and protein function, rather than an autoimmune response at the neuromuscular junction.
- Gout: This is a form of inflammatory arthritis caused by the deposition of uric acid crystals in the joints, leading to sudden and severe pain and swelling.