5 Discussion
IgG4-RD manifests as an autoimmune condition that prompts the growth of masses, frequently involving multiple bodily organs including the pancreas and the bile duct. Notably, an increase in blood serum IgG4 levels is detected in 55% to 97% of instances[1]. However, its occurrence within the gastric region is notably rare. Based on the 2019 American College of Rheumatology/European League Against Rheumatism guidelines for IgG4-RD classification, a diagnosis requires the affected organ to be characteristic of the disease, yet the gastrointestinal system is not encompassed within this criterion, rendering the diagnosis of IgG4-GID challenging[5]. Conversely, if we consider the Japanese criteria from 2011, they point towards a probable diagnosis of IgG4-RD in our patient[6]. It was called IgG4+ isolated or solitary lesions when patients were without top 5 of typical performance or other IgG4 associated diseases[7].
IgG4-GID is a rare condition that has been found in published case reports. The clinical presentations of IgG4-GID have been extensively studied and include gastric mass, ulcer, wall thickening, obstruction, and other symptoms. However, it is rare to find solitary gastric masses associated with IgG4-RD. To date, only 19 cases have been documented in scientific literature and most of them were discovered during physical examination. EUS is a popular method to further detect the mass and a multicenter survey revealed that inflammation primarily occurs in the muscularis propria in all cases[8]. IgG4-RID should be considered when a solitary gastric mass is detected and is found to originate from the muscularis propria.
A retrospective analysis of this case indicated that the gastric mass was larger than 2 cm, accompanied by gastrointestinal symptoms, and did not involve other organs, making resection a reasonable approach. Additionally, IgG4+ cells can also be found in calcifying fibrous tumour, gastric stromal tumor as well as other inflammatory and tumor diseases. Immunostaining did not detect vimentin or CD117, and diagnostic scans revealed the absence of disease in additional organs. With the high serum IgG4 level of eggs, a diagnosis of food-specific IgG4-GID is finally being considered. The mechanism of Food-specific IgG4-RD remains unclear, and diet therapy is usually the first treatment option, with hormone therapy even biological agents considered if symptoms persist or show improvement.
Solitary IgG4-GID cases are uncommon and typically arise from the muscularis propria. Diagnosis is often post-surgery, with the underlying mechanism still unclear. Most patients do not experience recurrence within one year of follow-up without hormone therapy. This case emphasizes the importance of considering preoperative biopsy for lesions originating from the muscularis propria to confirm the diagnosis and avoid invasive procedures. The decision to initiate hormone therapy should be made following the exclusion of non-IgG4-related diseases and a comprehensive evaluation of symptoms, involvement of multiple organs, and elevated serum IgG4 levels.The food-intolerance IgG4 test can be used for further evaluation, with dietary treatment as an initial option for asymptomatic patients.