Thymomatous myasthenia gravis among Hong Kong Chinese

Abstract

BACKGROUND: Myasthenia gravis (MG) is an autoimmune disorder targeting skeletal muscle acetylcholine receptor. Thymoma is associated in some patients with myasthenia gravis, the majority of whom present with symptoms of MG before detection of underlying thymoma. AIM: to study clinical and serological characteristics of Chinese thymomatous MG patients. METHODS: Autoimmune MG patients with thymomectomy and histologically confirmed thymoma followed up in our hospital for at least 12 months were studied. RESULTS: Total 37 Chinese MG patients with histology-proven thymoma were retrospectively studied. The mean MG symptom onset age was 48.5 years (range 25-81), 25 (68%) were female. The mean follow-up duration was 4.9 years (range1-15). MG symptoms preceded detection of thymoma in the majority (31 patients, 84%), in 6 patients thymoma detection preceded MG symptoms onset by 1-8 years. 19 patients (51%) had early onset MG (before 50 years of age). All patients were seropositive for acetylcholine receptor antibodies and 30 patients (81%) seropositive for striated muscle antibodies. Eleven patients (30%) had experienced myasthenic crisis and the worst MGFA clinical severity grade were class I (6 patients), class II (3), class III (8), class IV (9) and class V (11); hence 31 (84%) had generalized MG and 6 (16%) had ocular MG. 27 patients (73%) had history of corticosteroid therapy, 22 (60%) require azathioprine, 2 require other immunosuppressant (1 mycophenolate mofetil, 1 cyclosporin A). All 37 patients had good or satisfactory MG clinical outcome measured by MGFA post-intervention status (2 pharmacological remission, 23 minimal manifestation, 12 improved) though one patient died from metastatic thymoma. CONCLUSION: Thymoma MG was clinically severe with frequent myasthenic crises, but response to conventional immunosuppressive therapies are satisfactory.