IgG4-related disease with renal and orbital involvement: a clinical case.

Introduction: IgG4-related disease (IgG4-RD) is characterized by the growth of pseudotumors, which can affect almost every organ. Elevated serum IgG4 levels are present in only two-thirds of the patients and are not specific. Diagnosis is difficult and is usually based on a biopsy.

Clinical case: A 39-year-old man presented complaints of low back pain and fever. A renal computed tomography (CT) scan revealed a voluminous mass next to the right kidney and a biopsy showed an inflammatory process and excluded a neoplasm. A follow-up CT scan at four months revealed total regression without any treatment. Three years later, the patient presented with diplopia and right proptosis. MRI of the orbits revealed a retro-ocular mass; biopsy excluded a malignant process. Infectious, autoimmune or paraneoplastic diseases were also excluded. Although the patient's IgG4 serum levels were normal, histopathological reobservation of the renal biopsy revealed IgG4-positive plasma cells, thus confirming the diagnosis. The patient was prescribed a daily dose of 40 mg of prednisolone and regression of the right orbital lesion was observed.

Discussion: IgG4-RD is a rare and recently described condition. Most anatomic pathology laboratories do not routinely test for it. Spontaneous pseudotumor remission is possible, even when associated with the renal phenotype, although this has not been described until now.