[A patient with a relapse of myasthenia gravis after a 13-year remission following successful treatment by mediastinal irradiation and corticosteroid therapy].

We report a patient with myasthenia gravis who experienced a relapse 13 years after apparently successful treatment by mediastinal irradiation and corticosteroid therapy. A 20-year-old male was admitted to Shinshu University Hospital with a chief complain double vision and drooping eyelids. These symptoms had appeared 2 months prior to admission. They tended to be more severe late in the day, and varied from day to day. Prior to this admission the patient had been healthy for the 13 years since undergoing 45-Gy mediastinal irradiation and corticosteroid therapy. MRI and CT studies revealed no thymic hyperplasia. Total thymectomy was performed, and his myasthenic symptoms, including the opthalmoplegia, improved. Histological examination of the resected thymus revealed an active thymus with germinal centers. Immunohistological studies showed an abundance of intracellular adhesion molecule-1 (ICAM-1) in the germinal centers and thymic medullary epithelium, and the presence of lymphoid function-associated antigen-1 (LFA-1) in thymic lymphocytes. ICAM-1 and LFA-1 are ligand of adhesion molecules which interact with each other and play an important role in antigen presentation. Acetylcholine receptor (ACh-R) antigen is known to be present in the thymus. The presence of both ICAM-1 and LFA-1 in the active thymus in this patient suggests that these adhesion molecules may have a role in ACh-R antigen presentation, causing myasthenia. These findings suggest that patients with myasthenia gravis who do not undergo total thymectomy have a risk of recurrence, even after long-term remission.