Study On Diagnostic Value Of MHC Class I Staining In Idiopathic Inflammatory Myopathies

Objective:To study the expression of MHC class I antigen on the sarcolemma in IIM, which is absent in normal muscle tissue and to discuss the value of MHC-â… expression in the diagnosis and differential diagnosis of IIM.Methods:Expression of MHC class I antigens was studied in 45 muscle samples of 15 patients with IIM (14 polymyositis ,1 dermatomyositis) and 30 controls (5 normal subjects and 25 patients with various neuromuscular disorders) in a prospective blinded manner. And judge the consequence of staining of every sample and to calculate the expression rate of MHC-â… in every group and compare whether there is any difference. Furthermore, sensitivity and specificity of the expression rate of MHC-â… is calculated .Results:A diffuse pattern of staining was observed in all samples. Expression of MHC class I was found in 86.7% of muscle biopsies from patients with IIM. Expression of MHC class I was found in24% of the biopsies from patients with other neuromuscular disorders . No expression was detected in any of the patients in the healthy controls. The MHC-â… expression rate in IIM group is obvious higher than the control group(p<0.005). The sensitivity is 86.7%, and the specificity is 76%.Conclusions:In IIM, the expression of MHC-â… in muscle fiber is increased obviously , and both of the sensitivity and specificity are respectively high. So the immunohistological chemistry staining of MHC class I on the sarcolemma serve as a good pathological diagnostic test for IIM.