Myasthenia gravis: overlap with 'polyendocrine' autoimmunity.

81 patients with spontaneously acquired myasthenia gravis (MG) were investigated for the presence of autoimmune (AI) diseases and their sera were tested for a range of organ-specific autoantibodies. 77 of the patients were HLA-phenotyped. Antibody titres to acetylcholine receptors (AChR) were higher in non-thymomatous patients who possessed HLA-B8 (p less than 0.05) and/or -DR3 (p less than 0.05) as compared to patients lacking these HLA antigens. 3 out of 20 (15%) patients with ocular MG, 7/23 (30%) with generalized MG of early onset, 11/23 (48%) generalized MG of late onset and 5/14 (35%) patients with thymoma had either overt AI diseases or significant titres of organ-specific autoantibodies suggesting subclinical AI disease. In ocular MG, low titres and an infrequent finding of antibodies to AChR (32%) as well as the low prevalence of associated autoantibodies and AI diseases indicate that this subgroup of MG consists of patients with restricted AI reactivity. HLA-B8 and -DR3 were present in all the patients with associated AI disorders in the young onset group but in none of the patients with old age of onset. In the young group, 6 out of 7 patients with associated AI conditions were women whereas the sex ratio was about equal in the older cases in both, patients with and without associated AI diseases or autoantibodies. We conclude from these observations that ageing provides conditions that allow the breakdown of self tolerance. The simultaneous presence of HLA B8, DR3 and female sex provide important additional factors for early expression of MG.