ABSTRACT
ObjectiveTo explore the clinical and pathological features of hypomyopathic dermatomyositis(HDM).MethodsSix cases of HDM among 62 cases of dermatomyositis diagnosed between January 2008 and June 2010 were collected and analyzed.Four were women and 2 were men.The age of onset was between 45 and 65 years old,with disease duration of more than 6 months.All HDM patients presented with DM-specific skin lesions,but without muscle weakness.Serum creatine kinase(CK) level was within normal limits in 5 and mild elevated in 1.Electromyogram showed myogenic changes in 4 cases and normal in the other 2 patients.Muscle biopsies were carried out in the left biceps branchii in all of them.The muscle sectionswereprocessedwithstandardhistologicalprocedures,enzymehistochemistricaland immunohistochemical stains were carried out.The antibodies used for immunohistochemical stains were antiCD8,anti-CD20,anti-CD68,and anti-MHC-Ⅰ monoclonal antibodies.ResultsMuscle biopsies showed a variable amount of macrophages and B-lymphocytes infiltrating in the peri-mysium and fascicle area.Three of them presented with mild peri-fascicular fiber atrophy with fiber necrosis and regeneration.Lipid droplets increased mildly in muscle fibers.Capillaries distributing around perifascicular regions were darkly stained in nonspecific esterase stain.Perifascicular fibers showed immune-reactivity to MHC-Ⅰantibody.Conclusion The myopathological changes of HDM mimic classical dermatomyositis in some cases.HDM might be an intermediate presentation between pure amyopathic dermatomyositis and classical dermatomyositis.