What are Idiopathic Inflammatory Myopathies?

Dermatomyositis. This is characterised by proximal muscle weakness, in other words, it affects the muscles that are closest to the central part of the body. Patients often have difficulty getting out of a chair, climbing stairs, or raising their arms above their heads. Skin lesions on the face and hands are also typical.

Inclusion body myositis (IBM). It shows in people over 50 and t is characterised by distal muscle weakness, in other words, it affects the muscles furthest from the central part of the body, such as the quadriceps and the flexors of the fingers.

Immune-mediated Necrotising Myopathy (IMNM). This is characterised by rapid onset proximal muscle weakness.

Antisynthetase syndrome (AS). This is characterised by proximal weakness, involvement of the lungs (inflammation or fibrosis), and arthritis (inflammation of the joints), although not all patients have all three symptoms. Patients may also have a fever, Raynaud's phenomenon (colour change in the fingers and toes due to cold or stress), or flaking and cracking of the skin on the hands (known as 'mechanic's hands').

Myositis associated with another autoimmune disease (causing an overlap syndrome). This occurs when a patient has one of the types of myositis mentioned together with another autoimmune disease (including systemic lupus erythematosus, systemic sclerosis, vasculitis, and so on).

Polymyositis. Like IMNM, it presents as proximal muscle weakness, and these are distinguished according to the findings of the muscle biopsy.