Histopathological features of the idiopathic inflammatory myopathies

<p>In adult patients with presumed idipathic inflammatory myopathy (IIM) without a characteristic and diagnostic dermatomyositis rash, muscle biopsy is mandatory to confirm the IIM diagnosis and to exclude a myopathy which would not respond to glucocorticoids or other immunosuppressants, including inclusion body myositis. This chapter discusses when, where, and how to undertake muscle biopsies, when to repeat them, how to interpret their results, and how these relate to IIM subtypes and disease processes.</p>