Thymectomy was not considered for patients with purely ocular symptoms. Of the 65 thymoma patients, 17 (26%) also had HPL and nine had a malignant thymoma (table 1?1).). 300 (56%) patients, mostly those with MK-1439 thymoma (85%). In total, 441 patients (82%) showed an improvement. One\third of MK-1439 patients with HPL, a quarter of those with thymoma, one\fifth of those with a normal thymus and one\seventh of those not operated on went into remission. Conclusion The prognosis for the majority of patients with MG is favourable, irrespective of thymic histology. The cause may be the use of immunomodulating therapy. Myasthenia gravis (MG) is an autoimmune disorder of neuromuscular transmission.1,2 The prevalence of MG in Stockholm is 14.1 per 100?000 (17.1 for women and 10.8 for men).3 The thymus gland plays a central role in the development of the T cell repertoire but its role in MG is not clear.4,5,6 In MG, the thymic gland is normal in 15C20%, shows hyperplasia (HPL) in 65C75% and thymoma in 10C15% of patients.1,4 HPL is characterised by lymphoid follicles with germinal centres containing mostly B lymphocytes.4,5 In 1892, Hoppe reported on a 40\year\old man with typical myasthenic bulbar fatigability who died of respiratory paralysis. At autopsy, a large mediastinal tumour was revealed.7 In 1944, Blalock described six MG patients without a thymoma, in whom thymectomy was of benefit.8 Thereafter, thymectomy has MK-1439 been an accepted therapy for MG. No controlled study of its efficacy has been published but a controlled study was planned in 2000, presented in 20039 and has now started. Approximately 85% of patients with MG have circulating acetylcholine receptor antibodies (AChR\abs) in serum.10 Of patients with pure ocular MG, about 30% are seronegative. Genetic factors contribute to the susceptibility of MG with HPL, but seem to be of minor importance in thymoma associated MG.1,11 The aim of this study was to describe the clinical characteristics, coexisting malignant, autoimmune and endocrine disorders, presence of AChR\abs, use of immunosuppressive treatment (IS) and the response to it, in a population with MG with different thymic gland histology. Patients and methods The survey was performed in 2003C2006. A database on patients with MG was started in the 1970s which was approved by the Swedish Data Inspection Board and patients gave informed consent. Information was gathered retrospectively from 1956 and prospectively from 1975 concerning sex, age at onset of MG, age at thymectomy, method of operation, histology of the thymic gland, concomitant diseases, serum AChR\abs, clinical classification of MG, use of IS and the response to therapy. The information was added to this database after every visit to the MG centre. The majority (n?=?426) of patients lived in the Stockholm county area. This study describes 537 unselected patients with MG from a database of 681 patients. Only patients who were followed for at least 1.5?years were MK-1439 included. Most of the excluded patients lived outside Stockholm and were not available for interview or testing. The diagnosis of MG was based on abnormal muscular fatigability, positive response to cholinesterase inhibitors, abnormal results on neurophysiological tests and, in most patients, the presence of serum AChR\abs. Before 1970, the neurophysiological test comprised repetitive nerve stimulation with both low and high frequency stimulation, showing a decrement >5% between the 1st and 4th amplitudes of muscle action potentials. In 1970, the single fibre EMG was added. An increased jitter in at least 2 of 20 fibre pairs HVH3 MK-1439 was considered abnormal.12 Analysis of.