IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition. Accumulated research and data since 2003 have increasingly affirmed its classification as a systemic disease. Although IgG4-RD generally presents with involvement of one or several organ systems, it can affect almost any organ. The disease manifests gradually with the development of tumor-like lesions.
Constitutional symptoms, such as systemic fever and elevated inflammatory markers, are generally absent in association with this pathological condition. However, it is common for patients to exhibit allergy characteristics in addition to a slight increase in peripheral blood eosinophilia. The clinical manifestations of the disease exhibit variability on the specific organ system affected. Specific involvement of organs can ultimately result in organ failure. For example, retroperitoneal fibrosis commonly leads to post-renal failure [1]. The 2020 Revised Comprehensive Diagnostic (RCD) criteria for IgG4-RD include three components for diagnosis: clinical and radiological components (1), serological diagnosis (2), and unique pathological diagnosis (3). When all three are present it is a definitive diagnosis. The presence of components 1 + 3 constitutes a probable diagnosis, while the presence of components 1 + 2 indicates possible diagnosis [2].
Testicular involvement of IgG4-RD has been described in a few case reports. However, the uniqueness of our case is the manifestation of a testicular mass as a different target organ of relapse in a patient in remission from retroperitoneal fibrosis.