Background and purpose: Dermatomyositis (DM) with anti-nuclear matrix protein-2 (NXP-2) antibodies usually shows multifocal ischaemic lesions in muscle. Here, we aimed to investigate the microarteriopathy underlying muscle ischaemia in anti-NXP-2-positive DM.
Methods: A total of 16 patients diagnosed with anti-NXP-2-positive DM were investigated by muscle biopsy. A total of 13 patients with DM with other myositis-specific antibodies 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 and myxovirus resistance protein A (MxA). Electron microscopy was carried out to assess ultrastructure alterations.
Results: Subcutaneous edema, severe muscle weakness and dysphagia together with elevated creatine kinase, D-dimer and triglyceride levels, and decreased albumin levels were found in anti-NXP-2-positive DM. Muscle ischaemia included regional muscle edema, perifascicular atrophy, microinfarcts and focal punched-out vacuoles. The 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 vascular endothelial growth factor and MxA expression was observed in multifocal ischaemic lesions. MxA was present in endothelial and smooth muscle cells of the diseased arterioles and pericytes. Electron microscopy confirmed damaged capillaries and tubuloreticular structures.
Conclusions: Our research suggested that perimysial arterioles were most commonly involved in anti-NXP-2-positive DM, which led to muscle ischaemia.
Keywords: anti-nuclear matrix protein-2; dermatomyositis; myxovirus resistance protein A; perimysial microarteriopathy; vascular endothelial growth factor.
© 2019 European Academy of Neurology.