Myasthenia gravis (MG) severity and long-term prognosis in seronegative, seropositive, and thymoma MG were studied retrospectively in 4 previously reported series of age and sex-matched consecutive patients at Haukeland University Hospital, University of Bergen, Norway. Patients were assessed annually and were followed for 30 to 40 years. Fifty-two early onset cases (34 thymectomized and 18 non-thymectomized) were followed for 39 years. Thymectomized patients showed remissions in 21/34, whereas only 4/18 non-thymectomized patients had remission. The presence of AChR antibodies correlates with a more severe MG. With proper treatment, especially early thymectomy for seropositive MG, the outcome and long-term prognosis is good in patients with or without AChR antibodies. Thymectomy is of benefit in early-onset MG, but not in late-onset MG. In early-onset MG, thymectomy should be considered soon after onset, and outcome is not influenced by muscle autoantibodies. In 43 late-onset cases, MG severity did not differ between thymectomized (21 cases) and non-thymectomized patients (12 cases). Thymoma (24 cases) and non-thymoma (24) MG have equal severity and outcome of MG. Ryanodine receptor (RyR) antibodies in thymoma MG and titin/RyR in non-thymoma MG may indicate a less favorable outcome. 
COMMENT. Thymectomy is of benefit in early onset MG but not in late-onset MG. In a study of 51 MG patients (35 juvenile cases) at the Massachusetts General Hospital, 18 (86%) of 21 who underwent thymectomy showed complete or partial remission . Of 14 patients in this series who were treated with medication alone, 13 (93%) obtained remission, and initial results were comparable to those treated surgically. Remission was sustained in only 2 (14%) of drug treated vs 6 (29%) thymectomized patients. The earlier the surgery, the better chance of remission. 
Arthrogryposis multiplex congenita (AMC) is reported in 3 infants (including twins) born to a mother with MG.