This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Pathology
[{'content': 'A 55-year-old man complains of severe muscle weakness and drooping eyelids. He states that his symptoms worsen with repetitive movements but then resolve after a sho rest. A chest X-ray reveals an anterior mediastinal mass. A biopsy of this mass would most likely reveal which of the following pathologic changes? \nSelect and explain. \nA. B-cell lymphoma, B. Hodgkin lymphoma, C. Metastatic carcinoma, D. Thymic hyperplasia', 'role': 'user'}, {'content': 'Answer: D \nExplanation: - Given clinical features suggests the diagnosis of Myasthenia gravis. Myasthenia gravis -Acquired autoimmune disease characterized by abnormal muscular fatigability, caused by circulating antibodies to acetylcholine receptor at myoneural junction . -Manifests with ptosis (drooping eyelids) or diplopia (double vision) because of weakness in extraocular muscles. -Pattern of weakness is distinctly different from most primary myopathic diseases, in which there is relative sparing of facial & extraocular muscles. -Repetitive firing of muscles makes weakness more severe, whereas cholinesterase inhibitors improve strength markedly - diagnostically useful. - In 2/3rd of patients, thymic hyperplasia is closely associated with myasthenia gravis & 15% have thymoma. - Conversely, 1/3rd to 1/2 of patients with thymoma develop myasthenia gravis. - Thymectomy is often an effective treatment for these patients. - Cholinesterase inhibitors, immunosuppression, plasmapheresis can also be used in treatment.', 'role': 'assistant'}]