It is a well described phenomenon in the literature that a thymoma can lead to aplastic anaemia, and that a thymectomy can be curative for this. However, the opposite is extremely rare. We present an unusual case of a 60-year-old woman with myasthenia gravis, who was diagnosed with an incidental thymoma found on computerised tomography. Resection of the thymoma treated her myasthenia gravis, but led to an aplastic anaemia resistant to granulocyte-colony stimulating factor, cyclosporin and horse anti-thymocyte globulin treatment. The patient received an allogenic stem cell transplant but unfortunately passed away due to complications.