To describe demographic and clinical characteristics of Duke MG Clinic Registry patients who underwent thymectomy.

The Registry is a clinician-derived database that contains comprehensive information about patients seen in the Duke MG Clinic.

Data from 306 Registry patients who underwent thymectomy at Duke University Medical Center from 1975-2011 were reviewed.  All thymectomies were performed using open techniques. Not all data were available for all patients.

Among the 306 patients reviewed, 163 (53%) were female, 251 (83%) had acetylcholine receptor antibodies (AR-pos) and 53 (17%) did not (AR-neg). Muscle Specific Kinase (MuSK) antibodies were present in 13 AR-neg and 1 AR-pos patients; both antibodies were negative in 4. Antibody data were not available in 2.

Mean age at onset was 32±16 years in females and 43±19 in males, and was similar in AR-pos (37±19 years) and AR-neg (35±15 years) patients.  12 had ocular MG (OMG).  Mean disease duration at thymectomy was 3.19 years in AR-pos and 2.37 years in AR-neg patients.  Those with generalized MG (GMG) had shorter disease duration at thymectomy (3.0 years) than those with OMG (4.5 years).  The thymus was hyperplastic in 40% of both AR-pos and AR-neg patients.  Thymoma was present in 18% of patients, all of whom were AR-pos.  Mean follow-up after thymectomy was 7.3 years; 70% of AR-pos and 60% AR-neg patients achieved Minimal Manifestations or better by their last visit.  Pharmacologic or Complete Stable Remission was achieved by 27% of AR-pos, 22% of AR-neg, 24% of GMG and 64% of OMG patients.

We reviewed data in the Duke MG Clinic Registry from 306 MG patients who underwent thymectomy.  Thymic hyperplasia was the most common histologic finding regardless of antibody status or disease distribution.  Outcomes were favorable in all subgroups.  Further subgroup analyses are planned to characterize MuSK MG and double seronegative MG.