Objective: To investigate the immunopathological changes of micro-vessels in dermatomyositis.
Methods: Twelve patients with dermatomyositis, 5 males and 7 females, aged 40.8 (6 - 72), underwent muscle biopsy of biceps muscle of arm (n = 11) or deltoid muscle (n = 1). The specimens underwent routine histological, enzyme histochemical, and immunohistochemical staining and microscopy. Ten biopsy specimens from patients with other diseases were used as controls.
Results: Perifascicular atrophy of muscular fibers and inflammatory infiltration in perimysium were seen in all patients with dermatomyositis. Non-specific esterase staining showed deep staining of capillaries and micro vascular endothelium among the muscular fibers. Immunohistochemistry showed remarkable reduction of capillaries positive in von Willebrand factor (vWF), thrombomodulin (TM), and endothelial cell nitric oxide synthase (eNOS) in the perifascicular region, and low expression of .eNOS and TM in the microvascular endothelium in the perimysium.
Conclusion: The vascular lesions of dermatomyositis are located not only in capillaries, but also in other microvessels. Lower expression of TM and eNOS in vascular endothelium suggests the reduction of anticoagulation and vasodilation functions of vascular endothelium. Dermatomyositis is an inflammatory vascular endothelial disease.