Mixed connective tissue disease after thymectomy in refractory myasthenia gravis

Connective tissue diseases, including systemic lupus erythematosus (SLE) and systemic sclerosis are classic models of autoimmunity; diseases with large-scale loss of tolerance and subsequent development of pathogenic autoreactive lymphocytes and tissue targeting autoantibodies. Here we report a case of mixed connective tissue disease, with features of systemic lupus erythematosus and systemic sclerosis developing in a patient 10 years post thymectomy for myasthenia gravis. The patient developed acute cutaneous lupus, Raynaud’s with digital ulcers, arthritis and lymphopenia. Her myasthenia continued to be resistant to treatment and her rheumatic disease progressed despite aggressive therapy. We performed a database search of MEDLINE, EMBASE, Scopus, and Web of Science for articles of similar cases post thymectomy from inception to August 2021, using the terms “systemic lupus erythematosus” (or systemic sclerosis, or connective tissue disease) and “myasthenia gravis” and “thymectomy”. We identified 41 cases, 28 of SLE post thymectomy, 8 related to systemic sclerosis, 5 with mixed connective tissue disease and highlighted their different presentation and serology. We explore the role of the thymus, tolerance and myasthenia gravis in the development of connective tissue disease. This highlights the complexity of concurrent autoimmune diseases and their autoantibodies.