Dermatomyositis (DM) with anti-nuclear matrix protein-2 (NXP-2) antibodies usually shows multifocal ischemic lesions in muscle. Here, we aimed to investigate the microarteriopathy underlying muscle ischemia in anti-NXP-2 positive DM METHODS: Sixteen patients diagnosed with anti-NXP-2 positive DM were elevated by muscle biopsy. Thirteen DM patients with other myositis specific antibodeis and 11 normal controls were included for comparison. Immunofluorescence assays were performed to localize endothelial cells, smooth muscle cells and pericytes, and to determine lesions in myofibers and microvessels by vascular endothelial growth factor (VEGF) and myxovirus resistance protein A (MxA). Electron microscopy was carried out to assess ultrastructure alterations.Subcutaneous edema, severe muscle weakness and dysphagia together with elevated CK, d-dimer and triglyceride levels and decreased albumin levels were found were found in anti-NXP-2 positive DM. Muscle ischemia included regional muscle edema, perifascicular atrophy, microinfarcts and focal punched-out vacuoles. Density of arterioles was higher in anti-NXP-2 positive DM (P＜0.05). Perimysial arterioles with thickened vascular wall, thrombosis and lipid accumulation were found in the vascular wall of diseased perimysial arterioles. The frequency of diseased arterioles and thrombosis was higher in anti-NXP-2 positive DM (P<0.05). Sarcoplasmic VEGF and MxA expression was observed in multifocal ischemic lesions. MxA was present in endothelial and smooth muscle cells of the diseased arterioles and pericytes. Electron microscopy confirmed damaged capillaries and tubuloreticular structures.Our research suggested perimysial arterioles were most commonly involved in of anti-NXP-2 positive DM, which led to muscle ischaemia.
