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What is Involvement of which of the following muscles virtually excludes the diagnosis of polymyositis? and explain in detail?
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