Known radiologic findings suspicious for malignancy or infection that have not been investigated sufficiently
Rapid radiologic progression
Long bone abnormalities consistent with Erdheim-Chester disease
Splenomegaly
Pathologic
Cellular infiltrates suspicious for malignancy that have not been investigated sufficiently
Markers consistent with inflammatory myofibroblastic tumor:
near mucosal sites. Extensive neutrophilic infiltrates or neutrophilic abscesses strongly indicate the possibility of a non–IgG4-RD diagnosis.
Necrotizing vasculitis
Prominent necrosis:
Primary granulomatous inflammation
Pathologic features of a macrophage/histiocytic disorder
Specific disease exclusions
Crohn’s disease (if pancreatobiliary disease is present)
Ulcerative colitis (if pancreatobiliary disease is present)
Hashimoto thyroiditis (if the thyroid is the only proposed disease manifestation). Patients with IgG4-RD can certainly have Hashimoto thyroiditis
separately from IgG4-RD, but Hashimoto thyroiditis is part of the IgG4-RD spectrum.
IgG+ cells can be identified using either IgG staining or CD138 staining.
Head and neck gland involvement
Pancreas and biliary tree
Kidney
Hypocomplementemia pertains to low serum levels of C3, C4, or both.
Renal pelvic wall thickening can be either unilateral or bilateral, usually without severe stenosis or luminal irregularity.
Low-density areas in both renal cortices can be seen only on contrast-enhanced computed tomography and are usually patchy or
round-shaped in appearance.
Retroperitoneum
The location of IgG4-related retroperitoneal fibrosis or periaortitis is typically circumferential or on the anterolateral sides of the aorta. The
segment of aorta involved tends to be the infrarenal aorta, often extending to include the iliac vessels.
