This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pathology
[{'content': "In Raynaud's phenomenon which of the following change is seen in vessels in initial stage? \nSelect and explain. \nA. No change, B. Thrombosis, C. Fibrinoid necrosis, D. Hyaline sclerosis", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Raynaud phenomenon results from the exaggerated vasoconstriction of aeries and aerioles in the extremities, paicularly in the fingers and toes. The restricted blood flow induces paroxysmal pallor or cyanosis; involved digits characteristically show " red-white -and-blue " color change most proximal to most distal Robbins 9 th edition page no. 355', 'role': 'assistant'}]