Idiopathic inflammatory myopathies in dermatological practice (part I)

Idiopathic inflammatory myopathies (IIM) are characterized by proximal, skeletal muscle involvement of not fully elucidated immunological pathogenesis and, in part, by skin manifestations. The most frequent IIM seen by dermatologists is dermatomyositis (DM), affecting both adults and children. DM is identified by characteristic skin changes which commonly precede muscle weakness. In about 50% of cases dermatomyositis in adults is associated with internal organ malignancy, while in children such an association is not noticed. Of special interest for dermatologists are cases of so-called clinically amyopathic dermatomyositis, characterized by skin changes without symptoms of muscle involvement. In a proportion of these cases interstitial lung disease may develop. Of some diagnostic and prognostic value are myositis-specific antibodies (MSA) – Mi2 and anti-tRNA synthetase antibodies found in 5-20% of DM patients. Diagnostic and prognostic significance of newly detected MSA – CADM-145 and p-155 antibodies – is not fully known. Systemic corticosteroids are the initial treatment of choice, and various immunosuppressant drugs (e.g. methotrexate, azathioprine) and intravenous immuno­globulin are the second line agents. In the last few years, biological drugs – rituximab and TNF-αlpha antagonists – have been introduced. Further investigations on the efficacy of these drugs in IIM are necessary.