RYANODINE RECEPTOR ANTIBODIES ARE ASSOCIATED WITH SEVERE MYASTHENIA-GRAVIS

Sera from 32 thymoma patients, 29 of them with myasthenia gravis (MG), were tested for the presence of circulating antibodies to the ryanodi ne receptor (RyR) in Western blot, RyR is a channel protein essential for the excitation-contraction coupling in skeletal muscle. MG severit y was scored according to the Osserman classification during 1-17 year s of follow-up (mean 7 years). Fifteen patients (14 MG and 1 non-MG) w ere RyR-antibody positive. RyR-positive patients had a significantly h igher frequency of invasive thymomas (p = 0.01), and also a more sever e MC than RyR-antibody negative patients (p = 0,04). The use of immuno suppressive drugs at latest follow-up was more frequent in RyR-antibad y positive than in RyR- antibody negative patients (ft = 0.02). Thus t he presence of RyR-antibodies in thymoma patients is associated with a more severe disease and can be used as a prognostic marker.