This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S., Subject name: Medicine
[{'content': 'Involvement of which of the following muscles virtually excludes the diagnosis of polymyositis? \nSelect and explain. \nA. Neck muscles, B. Extraocular muscles, C. Esophageal muscles, D. Abdominal muscle', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. b (Extraocular muscles) (Ref. Harrison 18th/ ch. 388)POLYMYOSITIS# acquired myopathy characterized by subacute symmetrical weakness of proximal limb and trunk muscles# When a characteristic skin rash (violacious papules) occurs, the disease is known as dermatomyositis.# Patients often have dysphagia and neck muscle weakness.# Laboratory findings include an elevated serum CK level, an EMG showing myopathic potentials with fibrillations, and a muscle biopsy showing necrotic muscle fibers and inflammatory infiltrates.It is characterized by:# Symmetrical weakness of proximal limb muscles especially hips and thigh and later shoulder girdle.# Weakness of flexor muscles of neck.# Involvement of striated muscles of pharynx (dysphagia).# Involvement of respiratory muscles (late).# Ocular muscles are almost never affected# Facial muscles are unaffected in polymyositis.DERMATOMYOSITIS# characteristic Heliotropic rash: blue purple discoloration of upper eye lids with edema.# Gottronfs patch: Erythema of knuckles with a raised violaceous scaly eruption.# Flat red rash on face and upper trunk.# 'Sheet-like' soft tissue calcification", 'role': 'assistant'}]