PET/CT in patients with sarcoidosis or IgG4 disease

Sarcoidosis as a distinct disease entity was diagnosed more than 100 years ago. The signs and symptoms of the disease are nonspecific, posing a challenge for early and accurate diagnosis. IgG4 disease or syndrome has various clinical manifestations, such as sclerosing pancreatitis, sclerosing cholangitis, prostatitis, tubulointerstitial nephritis, interstitial pneumonia, and enlargement of salivary glands. This article discusses the role of the different diagnostic imaging modalities in sarcoidosis and IgG4 disease, including radiographs, computed tomography, magnetic resonance imaging, and conventional nuclear medicine, with a special emphasis on positron emission tomography as a superior modality for assessing these inflammatory diseases.