Positron Emission Tomography (PET) scanning is performed using the marker fluorine-18 (F-18) labeled FDG. FDG is 2-fluorodeoxyglucose, which is an analogue for glucose. Its uptake by cells reflects the metabolic activity in an anatomic region.
Sites that may be affected in IgG4-related plasmayctic syndrome:
(1) lacrimal and/or salivary glands (Mikulicz's disease)
(2) pancreas (autoimmune pancreatitis)
(3) retroperitoneum (retroperitoneal fibrosis)
(4) abdominal aorta (inflammatory aortic aneurysm)
(5) liver (cholangitis)
(6) kidneys (tubulointerstitial nephritis)
(7) pituitary (hypophysitis)
(8) thyroid gland (Riedel's thyroiditis)
The scan may give false negative results in late disease when there is advanced sclerosis and little inflammation.
The diagnosis of IgG4-related plasmacytic syndrome is supported by:
(1) an elevated serum IgG4 concentration
(2) an inflammatory cell infiltrate rich in IgG4-positive plasma cells
