Reverse 'see-saw' relationship between Graves' disease and myasthenia gravis; clinical and immunological studies.

Although the association of two distinct autoimmune diseases, Graves' disease (GD) and myasthenia gravis (MG), is rare, the relationships of clinical and immunological activities between the two diseases remain unknown. In the present study, we investigated whether there exist any relationships between clinical and immunological activities of GD and MG as well as any common characteristics of their HLA antigens in five patients with concomitant association with GD and MG. The present study clearly showed positive relationships between the clinical activities of GD and MG in all five cases. Except for two cases, one with undetectable acetylcholine receptor antibody and another with few sample number, there were positive relationships between two circulating auto-antibodies against TSH receptor and acetylcholine receptor as well as their immunological and clinical activities in the remaining three cases. Furthermore, the present serological HLA typing study revealed that all five cases had common HLA-DQ3. Therefore, our study clearly demonstrates a reverse 'see-saw' relationship between GD and MG based on their clinical and immunological features, and suggests that HLA-DQ3 may play a potential pathogenic role in the concomitant development of the two diseases.