METHODS

One hundred six myasthenic patients-78 females (73.5%) and 28 males (26.5%)-underwent therapeutical thymectomy by VATET (video-assisted trans-sternal extended thymectomy) at Policlinico “S. Marco”, Zingonia, Italy. MG diagnosis was established according to clinical, pharmacological, and electrophysiological criteria; anti-AChR Ab titer was measured using either fetal calf or human AChR. Anti-titin Abs were assayed by the ELISA method using the MGT-30 recombinant fragment of titin. 1 All sera were diluted 1: 200 in PBS. To determine the cutoff value, 58 control sera were tested in a single experiment. The mean optical density (at 450 nm) was 0.251 (SD 0.121), with a resulting cutoff of 0.614 (mean+ 3 SD)(Figure 1). Antiryanodine receptor Abs were assayed by Western blot analysis. 2 RyR was isolated from rabbit skeletal muscle, run on SDS-PAGE, and transferred to nitrocellulose sheets. The membranes were incubated for 2 hours with sera diluted 1: 50, washed with TBS-Tween 20 (0.05%), and incubated with peroxidase-conjugated rabbit antihuman IgG (1: 500). In each experiment, positive and negative control sera were included. Sera from 8 patients (one with thymic hyperplasia) were available for anti-titin Ab follow-up of at least one year after thymectomy. Statistical analysis was performed using a chi-square test, with a p value< 0.05.