Studies in myasthenia gravis: Effects of thymectomy: Results on 185 patients with nonthymomatous and thymomatous myasthenia gravis, 1941–1969

One hundred and eleven patients with myasthenia gravis and seventy-four patients with thymomatous myasthenia gravis underwent thymectomy between 1941 and 1969. Fifty per cent of the patients who achieved remission did so after a delay of two or more years. The time of onset of remission was directly related to the activity of the thymic germinal centers. In the nonthymoma patients remissions were stable and, with few exceptions, permanent. The percentage of patients in remission increased with each consecutive postoperative year, and 90 per cent of patients with a five year follow-up were in remission or had shown improvement. Sex, age and duration of symptoms had no marked influence on this trend. No death due to myasthenia occurred after the fourth postoperative year (excluding malignant thymomas); germinal centers were present in all the fatalities. These observations are consistent with the hypothesis that autoimmune diseases are due to abnormal clones of immunocompetent lymphocytes proliferating in the thymic germinal centers. In addition, the results suggest that thymectomy produces stable remission by eliminating these thymic centers; but its effect is delayed because of the long life span of the existing pool of small immunocompetent lymphocytes.