[Myopathy associated with anti-signal recognition peptide antibodies: Five case reports]

Five patients with myopathy associated with anti-signal recognition peptide antibodies, admitted to our hospital from December 2015 to June 2018, were chosen in our study, and their clinical and pathological manifestations and treatments were retrospectively analyzed. Five patients showed subacute or chronic onset and proximal limb muscle weakness. Serum creatine kinase level was significantly elevated. Immunoblotting assay confirmed the positive anti-signal recognition particle antibody. EMG prompted myogenic damage. Pathological features included muscle degeneration, necrosis with regeneration, visible atrophy and hypertrophic of muscle fiber, connective tissue hyperplasia and a small amount of inflammatory cell infiltration. Immunohistochemical staining showed necrotizing muscle fiber infiltrated with CD4-positive and CD8-positive lymphocytes and CD68-positive macrophages, and no CD20-positive lymphocytes and CD303-positive dendritic cells were observed. Two patients had expressed a bit of c5b-9 positive capillary. Anti-sarcoglycans staining, anti-dysferlin staining and dystrophin staining showed continuous strong positive expression. Follow-up study found that all patients were response to glucocorticoid, and a combination therapy of immunoglobulin and immunosuppression were necessary for some patients.