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IgG4-related diseases are new systemic autoimmune diseases discovered in Japan in the 21st century. Inflammation occurs in various organs throughout the body, and is characterized by the formation of hard lumps. Differentiation is important because symptoms similar to those of malignant tumors such as cancer may occur. In 2019, internationally unified diagnostic criteria were established, and recognition is gradually increasing.

IgG4-related diseases are characterized by inflammation in various organs throughout the body, and symptoms such as pain and functional decline. The affected organ varies from patient to patient. If the lacrimal and salivary glands are affected, swelling will appear around the eyes and jaw. When it occurs in organs such as the lungs, kidneys, and pancreas, the function of the organs declines. The average age of onset patients is about 60, and the number of patients in Japan is estimated to be in the tens of thousands. It is also designated as a national intractable disease.

Diagnosis of IgG4-related diseases is based on the "International Criteria for Classification of IgG4-related Diseases" established in 2019 led by Professor John Stone of Harvard University. The criteria divide the diagnosis into three steps:

Step 1 entry criteria:
Clinical presentation, radiographic findings and inflammatory pathology of lymphocytic and plasma cell infiltrates of 10 common organ lesions (pancreas, salivary gland, bile duct, orbit, kidney, lung, aorta, retroperitoneum, dura mater, thyroid) This disease is suspected based on the findings.

Step 2 Exclusion Criteria:
Exclusion criteria consisting of 5 items of clinical presentation, hematologic findings, imaging findings, pathological findings, and known diseases (e.g., ulcerative colitis, Crohn's disease, Hashimoto's disease) are confirmed. If no exclusions are allowed, proceed to step 3.

Step 3 Inclusion Criteria:
(1) histological findings, (2) IgG4-positive plasma cell infiltration in tissues, (3) serum IgG4 concentration, (4) lacrimal gland, parotid, sublingual, and submandibular gland lesions, ( Eight areas of findings are scored: 5) chest lesions, (6) pancreatic and bile duct lesions, (7) renal lesions, and (8) retroperitoneal lesions. For example, a serum IgG4 level between the upper limit of normal and twice normal is scored as 4 points, 2-5 times as high as 6 points, and more than 5 times as high as 11 points. If the total score of 8 items is 20 points or more, it is diagnosed as an IgG4-related disease.

Autoimmune pancreatitis, a type of IgG4-related disease, is a disease in which inflammation occurs in the pancreas. It often develops in elderly men, and symptoms such as exacerbation of diabetes, obstructive jaundice, pancreatic enlargement, and narrowing of the pancreatic and bile ducts are observed. You can Autoimmune pancreatitis and pancreatic cancer can be difficult to distinguish because the symptoms are similar. Until now, endoscopic retrograde pancreatography (ERP) has been essential for diagnosis because of the risk of complications of pancreatitis, but magnetic resonance cholangiopancreatography (MRCP) and endoscopic ultrasound With the widespread use of fine-needle aspiration cytology (EUS-FNA), it has become possible to distinguish between the two without performing ERP.

IgG4-related diseases are relatively rare diseases, so there are not many doctors who specialize in this disease. In addition, because it is a disease that spans multiple organs, it is necessary for specialists in each organ to treat it cross-organizationally. Against this background, in April 2023, Tokyo Metropolitan Komagome Hospital established the first center in Japan to specialize in treating IgG4-related diseases (Director: Terumi Kanzawa, Honorary Director of Tokyo Metropolitan Komagome Hospital). At the center, physicians from the departments of gastroenterology, collagen disease, ophthalmology, otolaryngology, nephrology, general medicine, radiology, and pathology work together to provide medical care. In the future, it is thought that other regions will also need a comprehensive medical approach in which doctors from various departments cooperate with each other.