Thymoma-Related Paraneoplastic Syndrome Mimicking Reactive Arthritis

Abstract

Background and Objectives: Thymomas are associated with a high frequency of paraneoplastic manifestations. Paraneoplastic syndrome (PNS) with thymoma presents a challenge to clinicians because of the need to decipher the association between the presenting symptoms and the underlying tumor. The condition most commonly noted in patients with PNS with thymoma is myasthenia gravis. Other common autoimmune diseases that may present as PNS include systemic lupus erythematosus, pure red cell aplasia, and Good syndrome. Seventy-six percent of patients with PNS-associated thymoma experience resolution of PNS after curing thymoma. Materials and Methods: A 37-year-old man with a two-month fever accompanied by polyarthritis accidently found thymoma after contrast computed tomography scans of his chest. He accepted Video assisted thoracoscopic surgery with resection of thymoma. Results: Fever and polyarthritis resolved after operation but recurred in five days due to cytomegalovirus viremia, which might be predisposed by previous antibiotics treatment before the diagnosis of thymoma. Conclusion: Patients with a thymoma also have a high frequency of PNS, and the most frequent condition found in patients with PNS-associated thymoma is myasthenia gravis. Fever with polyarthritis has been rarely reported as a symptom of PNS-associated thymoma. Here we reported an unusual case of PNS mimicking reactive arthritis with thymoma, as diagnosed based on the patient's clinical progression, imaging examination, and laboratory tests. The patient died of his comorbidities, and his death may have been related to long-term antibiotic use and consequent intestinal dysbiosis. This challenging case may help to inform clinicians of the need for detailed work-up of fever with unknown origin in the presence of chronic polyarthritis to prevent the overdiagnosis of inflammatory arthritis or rheumatic disease and avoid further comorbidities. Detailed work-up should include the patient's history of infections, inflammation, and malignant or nonmalignant tumors.

Keywords: paraneoplastic syndrome; reactive arthritis; thymoma.

Figure 1

A technetium-99m methylene diphosphonate bone scan revealed increased uptake in the left shoulder, elbow, wrist, and ankle, and right foot and toes.

Figure 2

A gallium-67 tumor scan indicated inflammation over left shoulder, left sternoclavicular junction, left interscapular region, lateral right hip region, left buttock, right knee, and left ankle, but no evidence of malignancy.

Figure 3

Computed Tomogram Scan with contrast at Chest revealed mass lesion over anterior mediastinum region.

Figure 4

A 7.2 cm × 5.6 cm × 4 cm mass identified after operation of Video-Assisted Thoracoscopic Surgery.

Figure 5

Microscopic appearance of the lesion. (a) Spindle epithelium mixed with small lymphocytes of the thymic tissue. (b) Immunohistochemistry (IHC) stains of cytokeratin revealed positive over epithelium component (c) IHC stains of CD 45 revealed positive for lymphocytes (d) IHC stains of CD5 revealed negative over epithelium component.

Figure 6

Ileus and hematochezia after 8 days of tumor resection. (a) Air-fluid level over transverse colon region (b) Sigmoid colon dilation.