Immunoglobulin G4-related disease (IgG4-RD) was not recognised as a systemic condition until 2003, when extra pancreatic manifestations were identified in patients with autoimmune pancreatitis. Since then, IgG4-RD has been described to involve virtually every organ system. It is highly responsive to immunosuppressants but can have detrimental effects if left untreated. Early recognition of the disease is, therefore, critical. The diagnosis of IgG4-RD is frequently challenging owing to its non-specific clinical manifestations, indolent nature and broad differential diagnoses. Although histopathological examination remains the cornerstone of diagnosis, imaging plays an important role in establishing extent of disease and identifying areas suitable for biopsy. 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) has been demonstrated to be useful in assessing organ involvement, guiding biopsy and monitoring disease response. The 18F-FDG PET/CT scan is highly sensitive and able to evaluate multiorgan involvement in a single examination, a key advantage over conventional imaging modalities. A potential pitfall is its low specificity. As such, detailed knowledge of the imaging findings in IgG4-related disease is required to avoid misdiagnosis. This pictorial review aims to depict the diverse spectrum of imaging findings of IgG4-RD and the key imaging features to distinguish it from other important differential diagnoses.

Recent data suggest that protective immunity from COVID-19 vaccine may wane after a period, with booster doses becoming increasingly deployed in many countries. An 84-year-old woman presents with a 6-month history of left upper-limb swelling; the only history of note was an intramuscular Pfizer-BioNTech mRNA vaccine booster in the ipsilateral deltoid just 1 week before the onset of the swelling. Upper-extremity lymphoscintigraphy after the administration of 99mTc-nanocolloid into the interstitial space of the hands showed left upper-limb lymphatic dysfunction.

No abstract

Background IgG4-related disease (IgG4-RD) is a heterogenous autoimmune disorder characterised by inflammatory lesions. Diagnostic imaging, such as FDG PET/CT, is critical in evaluation of the disease, especially for potentially lethal cardiovascular manifestations. This retrospective study examines the usefulness of semi-quantitative parameters of FDG PET/CT in monitoring IgG4-RD in patients with and without cardiovascular manifestations. Methods Patients diagnosed with IgG4-RD who underwent a FDG PET/CT scan were identified and classified based on presence or absence of cardiovascular disease. Clinical and laboratory data were extracted and compared to three FDG PET/CT semiquantitative parameters: standardised uptake value (SUV), metabolic tumour volume (MTV), and total lesion glycolysis (TLG). These data were also compared in patients before and after receiving immunosuppressive therapy. Results Forty-six patients identified were divided into an eight member subgroup of patients with cardiovascular manifestations, and a thirty-eight member subgroup of patients without. Patients with cardiovascular lesions were most frequently identified incidentally on imaging evaluation for other diseases (37.5%), with none presenting with chest pain or other cardiovascular symptoms. Ten patients with pre-treatment and post-treatment FDG PET/CT scans demonstrated significant decreases in all semiquantitative parameters, with no significant decrease in total IgG or ESR. The decrease in SUVmax, MTV, and TLG following therapy was replicated in patients with and without cardiovascular manifestations. Conclusion FDG PET/CT is an important investigation to determine all sites of involvement in this multisystemic disease, and to rule out life-threatening cardiovascular manifestations even in the absence of symptoms. Semi-quantitative parameters such as SUVmax, MTV, and TLG are useful in assessing treatment response in patients with or without cardiovascular manifestations. There are no serological substitutes that can quantify the extent of disease involvement like FDG PET/CT.

The concept of theranostics, where individual patient-level biological information is used to choose the optimal therapy for that individual, has become more popular in the modern era of 'personalised' medicine. With the growth of theranostics, nuclear medicine as a specialty is uniquely poised to grow along with the ever-increasing number of concepts combining imaging and therapy. This special report summarises the status and growth of Theranostic Nuclear Medicine in Singapore. We will cover our experience with the use of radioiodine, radioiodinated metaiodobenzylguanidine, peptide receptor radionuclide therapy, prostate specific membrane antigen radioligand therapy, radium-223 and yttrium-90 selective internal radiation therapy. We also include a section on our radiopharmacy laboratory, crucial to our implementation of theranostic principles. Radionuclide theranostics has seen tremendous growth and we hope to be able to grow alongside to continue to serve the patients in Singapore and in the region.