A case of limb-girdle type myasthenia gravis in whom rheumatoid arthritis appeared immediately after thymectomy

We report a 48-year-old female who presented limb-girdle type myasthenia gravis with inflammatory lung lesions and rheumatoid arthritis. She demonstrated a rapidly progressive muscle weakness of extremities. Neurological examination revealed facial muscle weakness, and proximal dominant limb muscle atrophy and weakness. Ptosis, ophthalmoplegia, and bulbar palsy were not observed. The edrophonium test and serum anti- acetylcholine receptor antibody were positive. The repetitive nerve stimulation showed 55% waning in the thenar muscles, From these findings, she was diagnosed as having myasthenia gravis. Plain chest X-P and body CT showed tumor-like lesions in the lung. Lung biopsy revealed the infiltration of lymphocytes. These lesions decreased in size after thymectomy and corticosteroid administration. Immediately after thymectomy, she began to have morning stiffness with pain and swelling of the finger and knee joints. RAHA test, which was negative before thymectomy, became highly positive. These findings were consistent with rheumatoid arthritis. In this patient, thymus probably played a role to suppress the development of rheumatoid arthritis.