Trata-se do sétimo relato da literatura mundial de casos de miastenia gravis em gêmeos homozigóticos em que ambos são acometidos. O homozigotismo foi provado com certeza por estudo de HLA e a forma adquirida da doença foi provada por determinação de níveis elevados de anticorpos anti-receptor de acetilcolina, havendo também níveis elevados de anticorpos antimúsculo estriado, sem outras evidências de timoma.

To the best of our knowledge this is the seventh case report of monozygotic twins both affected by myasthenia gravis (MG). The monozygotism was proven by sex identity, blood group and HLA determinations ('O' Rh +, A2, A19.2, B40, CW3). One paternal aunt was also affected and the three cases have high titles of anti-acetylcholine receptor antibodies and anti-striated muscle antibodies, which indicate an acquired form of MG. After several myasthenic crises the twins are now doing well with corticosteroid therapy. The paternal aunt has a more benign form of MG, with ocular and limb involvement (grade IIa of Osserman) and was submitted to thymectomy. The authors discuss the use of corticosteroid for the infantile form of MG instead of thymectomy, based on the immaturity of the immune system in the young age. The use of other immunosupressive drugs is not advisable because of potential hazardous development of neoplasms.