A pair of monozygotic twins who are concordant for myasthenia gravis but became discordant for systemic lupus erythematosus post-thymectomy.

We describe a pair of monozygotic twins who are concordant for myasthenia gravis but discordant for systemic lupus erythematosus (SLE). SLE developed in twin 1 18 years post-thymectomy and has been characterized by recurrent transverse myelitis and optic neuritis. Twin 2 remains well post-thymectomy, except for a skin rash and persistent leukopenia. Both twins have developed autoimmune thyroid disease. We review genetic and environmental factors of importance in the pathogenesis of SLE and discuss the possible role of thymectomy in the etiology of the disease.