Pôster:

Thymomas can be either asymptomatic, being diagnosed as incidental findings during imaging tests, or can be the cause of thoracic symptoms due to mass effect, or even the cause of paraneoplastic syndromes. In this report, we describe the clinical case of a patient with thymoma, in which the clinical findings were suggestive of inflammatory myopathy, with signs of myasthenia gravis, which lead to difficulty in reaching the diagnosis.

Case report

Our patient is a previously healthy 58 year old woman, who presented intense myalgia, generalized muscle weakness and progressive upper limb edema over the last 15 days. Physical examination showed ptosis of the right eye, and also upper limb muscle weakness and edema. Serum laboratory results were 8.744 ng/ml of CK, 685 IU/L of LDH and over 106 IU/L of aldolase. Due to strong suspicion of myositis, 1 mg/kg per day of prednisone was prescribed. Further investigation was performed through upper limb MRI, whose findings were compatible with inflammatory myopathy. Muscle-specific thyrosine kinase antibodies were negative, while Acetylcholine receptor antibodies were over 20 nmol/L. A thoracic CT was performed, which showed a mediastinal mass measuring 6.2 x 4.7 centimeters, as well as Superior Vena Cava compression. Biopsy of the mass was taken, and anatomopathology and immunohistochemistry study showed a B3 thymoma. The patient showed good clinical and laboratory response to corticotherapy and was discharged after 30 days of hospitalization. Considering the patient presented thymoma at stage group IVB, the treatment plan was to perform chemotherapy, with posterior evaluation in order to assess the possibility of surgical intervention.

Conclusion

In this report, we can observe clinical findings of myasthenia gravis, confirmed through the presence of AChR antibodies as a paraneoplastic syndrome of thymoma. This association is widely described in the literature. However, the patient’s signs and symptoms, as well as imaging and laboratory findings were strongly suggestive of inflammatory myopathy. Thus, we might consider this case an unusual presentation of the disease, where there is a possible association between two autoimmune disorders (inflammatory myopathy and myasthenia gravis), configuring paraneoplastic syndromes developed from the mediastinal mass.