IgG4-related disease with multiorgan involvement: a case-based review.

IgG4-related disease (IgG4-RD) is an immune-mediated multi-organ inflammatory disorder caused by tissue infiltration of lymphocytes with IgG4-secreting plasma cells. Herein, we discuss a case of a patient with IgG4-RD who had involvement of multiple organs: the kidneys, lymph nodes, bone marrow (biopsy performed), lungs, liver, and small intestine (imaging abnormalities). Although several case reports and series of IgG4-RD involving different organ involvement are in the literature, our patient has extensive simultaneous multi-organ involvement. We utilized the four domains (serologic, pathologic, radiologic, and pathologic) as discussed in the new 2019 ACR/EULAR classification criteria to provide a useful framework in considering an alternative tool for IgG4-RD in multi-organ involvement, where biopsy is more invasive and not always accessible. We highlight the findings of each organ involved that increase the likelihood that the patient has IgG4-RD. In our patient, the IgG4-RD classification criteria was fulfilled with total points adding up to 48. Our case meets the classification criteria for IgG4-RD, since at least one organ is involved to meet entry criteria (biopsy proven), no exclusion criteria are present, and the total points are ≥ 20. When such extensive involvement of IgG4-RD occurs, early diagnosis and treatment are recommended to avoid irreversible organ damage and better outcomes.