Long-term immunologic effects of thymectomy in patients with myasthenia gravis

Background: Thymectomy (Tx) is a common therapeutic option to treat myasthe nia gravis (MG), but its effects on the immune system are still obscure in humans. Objective: We sought to evaluate long-term immunologic effects of therapeut ic Tx in patients with MG. Methods: T- and B-cell subsets and T-cell repert oire were analyzed in 35 patients with MG, 16 with previous Tx (at least 8 years before), 6 with recent (<1 year) Tx, and 13 without Tx, as well as in 32 healthy subjects used as normal control subjects. Serum immunoglobulins and a variety of autoantibodies were also measured. A subsequent 3-gear cl inical follow-up was performed to verify the possible appearance of systemi c autoimmune diseases. Results: The long-term thymectomized (Txd) patients had mild T-cell lymphop enia and an expansion of some V beta families among circulating CD4+ and CD 8+ T cells. They displayed a normal number of total B and CD5+ B-circulatin g lymphocytes, but they also displayed a polyclonal increase in serum IgM a nd IgG associated with the presence of high levels of a variety of organ- a nd nonorgan-specific autoantibodies, including anti-dsDNA and anticardiolip in, without clinical evidence of autoimmune disease. These serologic abnorm alities mere not detectable in both non-Txd and recently Txd patients. Afte r 3 years, 2 long-term Txd patients had systemic lupus erythematosus and an undifferentiated connective tissue disease. Conclusions: The association between MG and laboratory findings of systemic autoimmune disease may be in part related to Tx rather than to MG. Tx may represent a risk for the development of systemic autoimmune disorders over years in patients with MG.