This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Myasthenia Gravis and Muscular dystrophy, Subject name: Medicine
A 65-year-old male comes to the OPD complaining of ongoing double vision which is worse when he is watching TV in the evening. He has also noticed that he feels weaker towards the end of the day and that his face is slightly puffy. On inspection, there is a paial ptosis of the left eye lid and his mouth hangs slightly open at rest. On examination, there are visibly distended neck veins. What is the most likely diagnosis? 
Select and explain. 
A. Myasthenia gravis, B. Lambe Eaton syndrome, C. Paraneoplastic cerebellar degeneration, D. Multiple system atrophy
A: Myasthenia gravis
Answer: A: Myasthenia gravis 
Explanation: Diagnosis : Double vision + Ptosis at the end of the day + weaker at the end of the day= Myasthenia Gravis Option B- Feels stronger at the end of the day. Option C- Presents with gait ataxia, nystagmus, head impulse test negative. Option D- Atypical parkinsonism associated with Cog wheel rigidity, Bradykinesia, Postural instability. Myasthenia gravis (MG) is a relatively common neuromuscular disorder that is caused by antibody-mediated autoimmune destruction of acetylcholine receptors at the neuromuscular junction(Post Synaptic) * Type V Hypersensitivity reaction > Type II Hypersensitivity Reaction. * Receptor of Acetyl choline are affected. It is a post junctional defect. Diagnosis: 1. Anti Ach Receptor blocking Antibody 2. Anti-MUSK Antibody 3. Anti LRP 4 Antibody 4. Single fiber electromyography (SFEMG)=Jitter and blocking - Confirmatory test 5. Repetitive nerve stimulation test. 6. Tensilon test, Or Anticholinesterase test. The treatment of MG may include: Anticholinesterase medications (Pyridostigmine), Immunosuppression, IVIg or plasmapheresis, Surgical intervention( Thymectomy).