Thymolipoma Association with Myasthenia Gravis: Case Report

BACKGROUND Thymolipoma, which was described initially by Hall in 1949, is an uncommon benign thymic tumor that represents around 9% of all thymic tumors. The incidence of thymolipoma is around 0.12 out of 100 000 cases per year, with a higher incidence in the younger age population. Thymolipoma incidence has been linked to different autoimmune diseases, including myasthenia gravis, in half of the reported cases. There are 34 reported cases in the literatures documenting such a relationship between thymolipoma and myasthenia gravis. The exact pathogenesis is unclear. However, some genetic findings revealed the presence of myoid cells, which might play a vital role in this association. CASE REPORT A 56-years-old female known to have myasthenia gravis presented to the Emergency Department with acute congestive heart failure, atrial fibrillation, and stroke secondary to infected vegetation from the mitral valve. The patient underwent a semi-urgent mitral valve replacement surgery treating her cardiac presentation along with an extended thymectomy to control her myasthenia gravis disease. The final histopathological assessment of the removed thymus revealed a thymolipoma pathology. CONCLUSIONS The possibility of thymolipoma as an anterior mediastinal mass should be kept in mind when dealing with an older age group of myasthenia gravis patients on steroids. Concomitant heart surgery and thymectomy are feasible, and extended thymectomy is the treatment of choice for thymolipoma in myasthenia gravis patients with a better complete remission rate after resection. However, further comparative studies are needed for a more reliable conclusion of the postoperative myasthenia gravis response after resection.