May 2026 Research Update

Across these papers, the overall pattern was that IgG4-related disease can be supported by a combination of blood tests and imaging, especially when symptoms and organ involvement are hard to interpret. One biomarker study suggested a specific blood signal can rise and fall with disease activity, while an imaging study suggested certain scan measurements may relate to how much disease is present and how soon it may return. [1] [2]

In a moderate-sized biomarker study, the protein CCL19 in blood was higher in people with IgG4-related disease than in controls and was one of a small set of proteins that separated patients from non-patients. CCL19 was also the only highlighted protein that clearly went down when treatment led to remission and went back up with relapse, and it tracked with clinical measures of disease activity. The authors reported CCL19 and blood IgG4 levels gave complementary information when distinguishing active disease from remission. [1]

In a prospective imaging study using a specialized PET/CT scan ([68Ga]Ga-FAPI-04 PET/CT), people described as having a proliferative subtype had higher scan uptake and larger overall lesion burden than those with a fibrotic subtype. The subtype label by itself did not show a clear difference in relapse-free survival, but higher scan-based measurements (such as higher target-to-background ratio or higher average uptake) were linked to shorter relapse-free survival. Uptake also varied by organ site, with higher values in pancreato-hepato-biliary involvement and lower values in lymph nodes. [2]

For patients, this set of studies is mainly background on how doctors may add information beyond standard blood IgG4 and routine imaging when diagnosing or following IgG4-related disease. The CCL19 work suggests one additional blood marker may help reflect when disease is active versus quiet, while the PET/CT work suggests some scan measurements may summarize how widespread or active disease appears and may relate to relapse risk. It is still uncertain how these approaches will be used in everyday care across different organs and settings, because the studies focused on specific tests and patient groups and did not establish a single universal approach. [1] [2]

Across the case-based papers, diagnosis relied on putting together organ-specific symptoms, imaging patterns, and tissue results, because IgG4-related disease can resemble cancer or other inflammatory conditions. These reports also showed that the most useful clues may differ by organ, and that rare presentations can create uncertainty when classic tissue thresholds are not met. Overall, the evidence here is exploratory because it comes from single-patient reports, a small imaging series, and a commentary. [3] [4] [5] [6] [7]

One case report described an 80-year-old man with severe kidney failure where diagnosis of IgG4-related kidney disease was supported by non-contrast ultrasound, CT, and MRI (including diffusion-weighted imaging), and confirmed by kidney biopsy showing IgG4-positive plasma cells and storiform fibrosis. The report highlights that non-contrast imaging approaches may still show multiple kidney lesions suggestive of inflammation when contrast is not feasible, but biopsy provided the deciding evidence in this patient. [3]

Two pancreatic mass case reports illustrated how IgG4-related autoimmune pancreatitis can look like pancreatic cancer on imaging. In one patient, the overall clinical and imaging picture, elevated blood IgG4, and improvement after a course of corticosteroids supported the diagnosis (the biopsy itself was inconclusive), and showed regression of pancreas and bile duct changes as well as kidney lesions. In another patient, the diagnosis was only made after pancreatic surgery, with postoperative pathology showing IgG4-positive plasma cells and fibrotic changes and no cancer, and the authors highlighted the diagnostic pitfall when tissue sampling is not done before major surgery. [4] [5]

A small retrospective imaging series of peripheral trigeminal nerve lesions proposed descriptive groupings based on CT and contrast-enhanced MRI patterns. IgG4-related disease appeared in the "Diffuse/Symmetric" grouping in one patient, described as long-segment, uniform, often bilateral thickening without a focal mass, which contrasted with more mass-like or infiltrative patterns seen in other conditions in the series. Because only one IgG4-related disease case was included, this pattern should be viewed as a possible clue rather than a firm rule. [6]

A commentary on a rare condition involving adult-onset asthma and periocular xanthogranuloma (AAPOX) linked to IgG4-related disease emphasized that a lower-than-expected IgG4/IgG tissue ratio may not fully exclude IgG4-related disease in this setting. It highlighted a combined clinical, imaging, and blood-test approach when biopsy results are not definitive, and noted that the usefulness of a single ratio threshold may vary by organ and subtype. This was a discussion piece rather than a new patient study. [7]

For patients, these reports underscore why IgG4-related disease can take time to diagnose when it presents as a mass or as organ-specific damage, especially in the pancreas and kidneys where other serious conditions may look similar. They also show how much weight may be placed on tissue examination when imaging is not specific, and why rare presentations (such as periocular disease with asthma or nerve involvement) may require more flexible interpretation of test results. What remains uncertain is how often these individual patterns apply to other patients, since most of the evidence here comes from single cases and a small series. [3] [4] [5] [6] [7]

Across these reports (all single-patient case reports), imaging sometimes suggested advanced cancer, but tissue examination later showed IgG4-related disease (IgG4-RD) causing mass-like changes, scarring, or inflammation. At the same time, some cases showed the opposite problem: a cancer or lymphoma was ultimately found even though early test results or biopsy patterns looked consistent with IgG4-RD. Overall, the pattern was that scans and even limited biopsy samples may not fully separate inflammation from cancer, so the final explanation depended on careful pathology and, in one report, molecular testing. [8] [9] [10] [11] [12] [13]

In the kidney area, one man had a scan that appeared to show kidney cancer spreading into nearby tissues, leading to kidney removal; pathology instead found a small kidney cancer confined to the kidney plus nearby IgG4-related retroperitoneal fibrosis that had mimicked cancer extension on imaging. After surgery, steroid treatment improved the IgG4-RD changes, and there was no reported cancer recurrence. [8]

In the gallbladder, imaging strongly suggested gallbladder cancer in a 77-year-old man, but after extensive surgery, pathology showed isolated IgG4-related cholecystitis (inflammation of the gallbladder) with many IgG4-positive immune cells. The patient remained free of disease for 5 years without steroid treatment, showing that IgG4-RD can closely copy a cancer picture on multiple imaging tests. [9]

Several reports highlighted that IgG4-RD-like features can also hide a true cancer or occur at the same time. A woman with a liver-area mass had a biopsy showing many IgG4-positive cells and had only temporary shrinkage on steroids, but surgery and MDM2 gene amplification testing confirmed a dedifferentiated liposarcoma that had infiltrated nearby tissues. [10]

Two reports focused on lymphoma in the setting of IgG4-RD. One patient had IgG4-RD and a lung lesion that biopsy proved was marginal zone lymphoma, and two different scan types showed different uptake patterns in the lung versus a brain lesion that had been suspected to be a meningioma. Another patient with long-standing IgG4-RD (and a separate blood condition) developed a very large kidney mass that biopsy confirmed as aggressive diffuse large B-cell lymphoma, while blood IgG4 levels stayed high. [11] [12]

IgG4-RD can also cause multi-organ inflammation that forms masses and causes severe symptoms without cancer being present. One man had kidney inflammation, a pancreatic mass that mimicked cancer, and gastrointestinal protein loss causing swelling and diarrhea-like fatty stools; imaging of the pancreas later no longer showed the mass appearance, and symptoms improved after immune-suppressing treatment, although low blood protein levels persisted. [13]

For patients and caregivers, these reports are mainly background about why IgG4-RD can be confusing when scans show a mass or cancer-like spread: inflammation and scarring from IgG4-RD can look malignant, and in some people a true cancer or lymphoma may still be present. Because all the evidence here comes from individual cases, it cannot tell how often these situations happen, which tests work best, or who is at risk. What is clearest is the shared message that the most reliable answers in these cases came from tissue-based evaluation (and, in one case, additional molecular testing), not from imaging alone. [8] [9] [10] [11] [12] [13]

Across these three single-patient reports, IgG4-related disease affected the kidneys and urinary tract in several distinct patterns: kidney filter disease causing marked protein loss in the urine, inflammation in the kidney tissue itself, and scarring in the back of the abdomen that squeezed the ureters and blocked urine flow. A consistent message was that blood IgG4 levels were not always high, so tissue biopsy and imaging were important in confirming the cause. Because these are case reports, they show what can happen in individual people but cannot predict what will happen for most patients. [14] [15] [16]

One report described IgG4-related membranous nephropathy (a kidney filtering problem) without the more typical kidney tissue inflammation, leading to severe protein loss and low blood albumin; after treatment with prednisolone and rituximab, urine protein levels fell and kidney function improved. The same patient had earlier pancreas problems and later stomach tissue changes consistent with IgG4-related disease, showing that kidney issues may appear after other organ symptoms. [14]

Another report described a rare overlap: ANCA-associated nephritis occurring together with IgG4-related tubulointerstitial nephritis (inflammation in the kidney tissue between the filters). Even though the serum IgG4 blood test was normal, the kidney biopsy showed many IgG4-producing plasma cells, and kidney function and inflammation markers improved after corticosteroids and rituximab. [15]

A third report showed IgG4-related retroperitoneal fibrosis causing physical blockage of both ureters, leading to obstructive acute kidney injury with very high creatinine and episodes of no urine output. Kidney function improved quickly after urgent urine drainage (stents and later nephrostomy tubes), and the IgG4-related diagnosis was supported by biopsy and imaging despite normal serum IgG4; infection had to be managed alongside these kidney and urinary procedures. [16]

For patients and caregivers, this set of reports is mainly background about the range of ways IgG4-related disease can involve the kidneys and urinary tract, from protein leaking into urine to inflammation or urinary blockage. They also highlight that a normal blood IgG4 level does not rule out IgG4-related kidney disease in these individual cases, and that biopsy and imaging were key to sorting out the cause. What remains uncertain is how often these patterns occur, how reliable different tests are across broader patient groups, and which approaches work best in the long term, since the evidence here comes from three individual cases.

Across a long-term multicenter follow-up study and a nationwide survey, autoimmune pancreatitis often responded to steroid treatment but relapse built up gradually over many years. [17] [18] At the same time, long-term tracking raised two practical concerns: changes in blood sugar control and signs of worsening nutrition over time, even when early lab results looked better. [17]

In 83 people with type 1 autoimmune pancreatitis followed for at least 10 years after steroid treatment, relapse continued to accumulate, reaching 56.9% by 10 years. [17] In this study, stopping steroids predicted relapse, while having IgG4 blood levels that were normal at diagnosis or became normal after treatment was linked with fewer relapses. [17]

The same long-term study did not show a higher overall cancer risk compared with the general population, although pancreatic cancer risk was numerically higher in their estimates. [17] Over 10 years, average HbA1c (a longer-term blood sugar marker) improved at 3 years but tended to worsen by 10 years, and serum albumin (a nutrition-related blood protein) declined by 10 years. [17]

A nationwide Japanese survey estimated 16,750 people living with autoimmune pancreatitis in 2021 and reported long-term relapse rates that continued rising with time (for example, 36.0% at 10 years). [18] In this dataset, most patients received glucocorticoids initially and most also received maintenance therapy, and malignancies accounted for 40% of deaths among those who died during follow-up. [18]

Two single-patient reports highlighted how autoimmune pancreatitis can connect to other health issues and may not always fit a simple pattern. One 65-year-old man was described as having diabetes linked to possible IgG4-related disease presenting as type 1 autoimmune pancreatitis, with good clinical and imaging response to corticosteroids. [19] Another report described a 28-year-old man with suspected type 2 autoimmune pancreatitis together with autoimmune hepatitis; a pancreatic biopsy was not diagnostic, and the diagnosis relied on the overall picture from imaging and blood tests, followed by monitoring on prednisone and tacrolimus. [20]

For patients and caregivers, this group of studies mainly adds background about what can happen over years after autoimmune pancreatitis: relapse risk can remain for a long time, overall cancer risk may not be higher in some long-term data, and blood sugar and nutrition-related labs may drift in an unfavorable direction later even if they improve early on. [17] [18] What remains uncertain is how well these long-term patterns apply to each individual, especially across different autoimmune pancreatitis subtypes and healthcare settings, and the case reports are useful for awareness but cannot predict outcomes for most people. [19] [20]

Across these reports, steroid-based treatment was linked to high early improvement in many people with IgG4-related disease, including those with more than one organ involved. However, keeping the disease quiet over time was harder, with relapses reported and some patients needing longer-term add-on medicines to maintain control. [21] [22] [23] [24]

In a 60-person adult study from Western India (moderate-strength evidence), most patients improved by 6 months after starting steroids along with steroid-sparing medicines, but relapses were frequent later on. Relapse was reported in 66% of patients, with a median time to relapse of 13 months. [21]

In that same adult cohort, a very small subgroup receiving rituximab plus methotrexate had fewer relapses reported over 2 years, but only four people were included so it is uncertain how well this applies to others. One death from urosepsis was reported in the overall group. [21]

In a six-child case series (exploratory evidence), most children had improvement on treatments that included steroids and other immune-suppressing medicines such as mycophenolate mofetil, cyclophosphamide, or rituximab. One child had multiple relapses on topical steroids that improved after switching to systemic cytostatic therapy, and some children had only partial remission and needed ongoing biologic therapy. [22]

Two single-patient case reports described rapid improvement after steroid treatment despite normal blood IgG4 levels, including one patient with liver inflammatory pseudotumor lesions and another with multi-organ involvement (kidneys, salivary gland, lungs, lymph nodes, and retroperitoneum). These reports suggest that blood IgG4 can be normal even when tissue inflammation responds to treatment, but single cases cannot predict what will happen for most patients. [23] [24]

For patients and caregivers, this set of studies reinforces two practical points for understanding current care: many people improve after starting steroid-based treatment, but returning disease activity (relapse) can still happen and may require longer-term strategies using additional immune-suppressing medicines. It also highlights an uncertainty that matters in day-to-day discussions: a normal blood IgG4 level did not rule out treatment-responsive disease in several reports, so clinicians often rely on biopsy and the full clinical picture when planning follow-up. [21] [22] [23] [24]

This group of papers shows that IgG4-related disease can involve the nervous system coverings (around the brain or spinal cord), the ear, and the heart or major blood vessels, sometimes causing symptoms that look like other conditions. In these single-patient reports, doctors relied on a mix of biopsy results, blood IgG4 levels, and imaging tests to support the diagnosis and to track response over time. Overall, symptoms and imaging findings tended to improve after corticosteroid treatment, and several reports described adding a longer-term immune-suppressing medicine when disease returned or when longer-term control was needed. [25] [26] [27] [28] [29]

For nervous system involvement, two reports described thickening and inflammation of the protective layers around the brain or spinal cord (hypertrophic pachymeningitis), leading to major symptoms. One person had spinal cord compression with weakness and sensory changes, needed urgent decompression surgery, and then improved on prednisolone plus azathioprine after symptoms returned when steroids were stopped because of side effects. [25]

Another person had brain-related symptoms including attention and language problems, and imaging showed inflammation involving the dura and the brain surface layers; a dural biopsy supported IgG4-related disease. After prednisolone, the thickened dura and abnormal brain-surface signals on MRI resolved and higher-brain function improved in that individual. [26]

For ear involvement, one report described a person whose IgG4-related disease showed up mainly as ear symptoms with conductive hearing loss and recurrent middle-ear problems. Hearing improved with prednisone but worsened during taper, and later the person was treated with inebilizumab along with tapering off prednisone, with about a 20% hearing improvement and no recurrent ear or sinus symptoms reported at follow-up. [27]

For heart and vessel involvement, two reports suggested IgG4-related disease may contribute to myocarditis (heart muscle inflammation) or to coronary and valve disease with inflammation of the aorta. In one person with chest pain and elevated troponin, heart scans showed swelling and scarring patterns consistent with myocarditis despite non-obstructed coronary arteries, and the person improved after restarting prednisone and then using mycophenolate mofetil for maintenance (without a heart biopsy, so the cause was considered probable). [28]

In another person, repeated coronary problems and valve dysfunction were ultimately tied to IgG4-related disease affecting multiple organs, supported by tissue findings in the aortic wall showing many IgG4-positive plasma cells and a typical fibrosis pattern, along with imaging and blood tests. The person underwent aortic valve replacement and then started steroids plus mycophenolate, highlighting that heart involvement may require combined input from cardiology, surgery, and rheumatology in complex cases. [29]

For patients and caregivers, these papers mainly serve as background examples of how IgG4-related disease can show up outside more commonly discussed organs, including symptoms involving movement or sensation (spinal), thinking or language (brain coverings), hearing (ear), and chest pain or heart function changes (heart and vessels). Because all five papers are single-patient case reports, they cannot show how often these problems happen or predict outcomes for most people; they do show that doctors often combine biopsy (when available), blood IgG4, and imaging to clarify what is going on and to follow changes over time. Important uncertainties remain, including how confidently IgG4-related disease can be named as the cause when a biopsy is not possible (as in the myocarditis report) and which long-term immune-suppressing approaches work best across different organ sites. [25] [26] [27] [28] [29]

Across these reports, IgG4-related disease sometimes appeared together with other immune-driven illnesses or in unexpected organs, which can blur the clinical picture and make it harder to name the underlying cause of symptoms. Because all the evidence here comes from a few individual cases, it is not clear how often these overlaps happen or whether they share a common cause.

One case described a 68-year-old man first labeled as having IgG4-related disease who improved strongly on steroid treatment, but later had genetic testing that confirmed VEXAS syndrome (a separate inflammatory condition). The authors reported the two conditions as coexisting, but noted that the first IgG4-related disease diagnosis may have been a misclassification. The report highlights that blood count problems (like low blood cells) and ongoing inflammation can be clues to an overlapping condition, although this is based on a single patient. [30]

Two additional cases described people who had both IgG4-related disease and systemic lupus erythematosus (lupus). The authors emphasized that the shared features between the two diseases can create diagnostic uncertainty, and that carefully separating what is due to which condition may matter for understanding the illness picture. [31]

A separate case report showed that IgG4-related disease can involve the appendix and look like acute appendicitis, with the diagnosis made on the removed tissue under the microscope. The patient recovered without complications after surgery and remained well at one year, but this is one report and does not show how typical this course is. [32]

For patients and caregivers, these reports mainly serve as background about why diagnosis can sometimes be complicated: symptoms and test results may reflect more than one immune condition, or IgG4-related disease may show up in an unexpected organ. The uncertainty is that case reports cannot tell how common these situations are, which warning signs are most reliable, or whether the conditions are biologically connected.