Target Proteins in Human Autoimmune Rippling Muscle Disease

Abstract

Rippling muscle disease (RMD) is a rare disorder of the striated muscle characterized by signs and symptoms of muscular hyperexcitability induced by stretch or by percussion (Torbergsen 2002; Vorgerd et al., 1999). Though RMD is generally benign also severe forms of the disease are known. Several reports show a diversity of autosomal-dominant, autosomal-recessive and sporadic RMD forms as well as acquired RMD in association with myastenia gravis or with thymoma. There are few reports on patients with rippling muscle and the presence of autoantibodies directed against striated muscle responding to immunosuppressive treatment. A patient from Japan showed a form of RMD that preceded a lymphoplasmacytoid lymphoma. Up to now it is unclear which structures of the striated muscle are the targets of the immune response leading to the clinical phenotype of RMD. To identify targets of the autoimmunological reactions against different proteins of the functional structure of the sarkolemma different methods were applied to muscle biopsies and serum samples of 10 patients. Methods included immunohistochemistry, elisa technique, western blots of muscle proteins and DNA sequencing of the two coding exons of CAV3 as well as the muscle specific exon of BIN 1. Mutation analysis showed no unregular sequences of the DNA. However the main targets seemed to be caveolin 3 and BIN 1. Further studies are needed to eluminate the protein domains responsible for the autoimmune reaction.