Interstitial lung disease in an adult patient with dermatomyositis and anti-NXP2 autoantibody.

Idiopathic inflammatory myopathies (IIMs) are characterised by inflammatory involvement of skeletal muscles causing weakness and pain, with possible associated systemic manifestations including frequent interstitial lung disease (ILD), and significant morbidity and mortality. Accumulating evidence suggests an important contribution of autoimmune responses to the pathogenesis of these diseases. Autoantibodies are present in at least half of patients with IIMs [1]. Some of these autoantibodies are frequently detected in patients with other connective diseases associated with myositis (especially systematic sclerosis) and are referred to as myositis-associated autoantibodies, whereas others are considered specific to IIMs and are referred to as myositis-specific antibodies (MSAs), including antibodies against aminoacyl transfer RNA (tRNA) synthetases, Mi-2 (a nuclear helicase) and the signal recognition particle [1, 2]. MSAs, when present, contribute to the diagnosis of IIM, especially in patients with mild muscle involvement or with ILD pre-existing to the myositis, although other, nonspecific antibodies are associated with various frequencies of manifestations and distinct clinical phenotypes within the spectrum of IIM [1, 2]. Novel targets of autoantibodies have recently been described in IIM patients without “classical” MSAs, including p155/140 (transcriptional intermediary factor (TIF)-1-γ), CADM-140 (melanoma differentiation-associated gene 5), small ubiquitin-like modifier activating enzyme (SAE)1 and SAE2, and nuclear matrix protein 2/MJ (NXP2) [3].