Polymyositis.

Polymyositis

Overview
inflammatory disorder causing symmetrical, proximal muscle weakness
thought to be a T-cellmediated cytotoxic process directed against muscle fibres
may be idiopathic or associated with connective tissue disorders
associated with malignancy
dermatomyositis is a variant of the disease where skin manifestations are prominent, for example a purple (heliotrope) rash on the cheeks and eyelids
typically affects middle-aged, female:male 3:1

Features
proximal muscle weakness +/- tenderness
Raynaud's
respiratory muscle weakness
interstitial lung disease: e.g. fibrosing alveolitis or organising pneumonia
dysphagia, dysphonia

Investigations
elevated creatine kinase
EMG
muscle biopsy
anti-Jo-1 antibodies are seen in pattern of disease associated with lung involvement, Raynaud's and fever