Clinical and pathological features of patients with antineutrophil cytoplasmic antibody-associated vasculitides concomitant with IgG4-related disease

Deciphering three predominant biopsy-proven phenotypes of IgG4-associated kidney disease: a retrospective study

Background

IgG4-associated kidney disease (IgG4-RKD) encompasses a spectrum of disorders, predominantly featuring tubulointerstitial nephritis (TIN) and membranous glomerulonephropathy (MGN). The limited understanding of the co-occurrence of IgG4-RD-TIN with anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) poses a diagnostic and therapeutic challenge.

Methods

We examined 49 cases, comprising 21 cases of IgG4-RD-TIN (group A), 10 cases of IgG4-RD-TIN accompanied with MGN (group B), and 18 cases of IgG4-RD-TIN concurrent with AAV (group C), at the First Affiliated Hospital of Zhejiang University, China, from June 2015 to December 2022.

Results

The mean age and gender of the three IgG4-RKD subtypes were not statistically significant. IgG4-RD-TIN exhibited higher serum creatinine and a higher incidence of hypocomplementemia (group A 47.6%, group B 30%, group C 16.7%). IgG4-RD-TIN-MGN was characterized by proteinuria (group A 0.3 g/d, group B 4.0 g/d, group C 0.8 g/d, P < 0.001) and hypoalbuminemia. IgG4-RD-TIN-AAV exhibited hypohemoglobinemia (group A 103.45 g/l, group B 119.60 g/l, group C 87.94 g/l, P < 0.001) and a high level of urine erythrocytes. The primary treatment for IgG4-RD-TIN was steroids alone, whereas IgG4-RD-TIN-MGN and IgG4-RD-TIN-AAV necessitated combination therapy. Group A experienced two relapses, whereas groups B and C had no relapses. There was no significant difference in patient survival among the three groups, and only two cases in group C suffered sudden death.

Conclusions

This study provides valuable insights into clinical manifestations, auxiliary examination features, pathological characteristics, and prognosis of IgG4-RD-TIN, IgG4-RD-TIN-MGN, and IgG4-RD-TIN concurrent AAV. Large-scale studies are required to validate these findings.

Coexistence of IgG4-related disease and ANCA-associated vasculitis: case report and review of the literature

IgG4-related disease (IgG4-RD) is a fibroinflammatory condition that is characterized by storiform fibrosis, infiltration of IgG4-positive lymphocytes, obliterative phlebitis, and high IgG4 levels. Since IgG4-RD affects a wide variety of organs, a differential diagnosis must include multiple conditions. IgG4-RD is also believed to coexist with certain diseases. In recent years, case reports and case series describing the co-occurrence of IgG4-RD and ANCA-associated vasculitis (AAV) have been published. We intended to evaluate patients with IgG4-RD and AAV overlap in the literature using a case similar to one that was diagnosed and monitored in our department. We searched the databases of Web of Science, Scopus, and Google Scholar as well as PubMed with the keywords ANCA, IgG4, IgG4-RD, granulomatosis with polyangiitis, Wegener's granulomatosis, microscopic polyangiitis, Eosinophilic granulomatosis with polyangiitis, and Churg-Strauss syndrome. Cases and Case series addressing the coexistence of IgG4-RD and AAV have been selected. Comprehensive diagnostic criteria are used to diagnose IgG4-RD. The Chapel Hill Consensus Conference nomenclature criteria were used for the inclusion of AAV. Out of a total of 910 publications, 20 articles, including 65 cases, were found to be eligible. Forty-seven cases with IgG4-RD were evaluated as definitive (71.2%), 10 cases as probable (15.1%), and 9 cases as possible IgG4-RD (13.6%). 26 patients were diagnosed with GPA, 1 patient with localized GPA, 23 patients with MPA, and 4 patients with EGPA. The aorta, lacrimal tissue, pancreas, and retroperitoneum are the sites of IgG4-RD rather than AAV. AAV and IgG4-RD might coexist in the same patient. IgG4-RD is mainly associated with GPA.

Clinical phenotypes and prognosis of IgG4-related diseases accompanied by deteriorated kidney function: a retrospective study

INTRODUCTION

IgG4-related disease (IgG4-RD) is a multiorgan autoimmune disorder that causes irreversible injury. Deteriorated kidney functions are common but easily ignored complications associated with IgG4-RD. Yet the clinical manifestations and prognosis of this specific entity have not been fully illustrated.

METHOD

Three hundred fifty patients with IgG4-RD were retrospectively enrolled and divided into 119 IgG4-RD with chronic kidney disease (IgG4-RD CKD+) and 231 IgG4-RD without CKD (IgG4-RD CKD-). Demographic clinical and laboratory characteristics and survival of two cohorts were compared using restricted cubic splines, logistic and Cox regression, and Kaplan-Meier analysis. A nomogram was generated for calculating the probability of CKD in IgG4-RD.

RESULTS

The spectrum of organ involvement was different between IgG4-RD CKD+ and CKD- cohorts (p<0.001). Lung (26.89%) and retroperitoneum (18.49%) involvement were more common in the IgG4-RD CKD+ cohort. Increased serum potassium and phosphorus, reduced calcium levels, and hypocomplementemia (all p<0.05) were observed in IgG4-RD CKD+. Restricted cubic splines revealed a U-shaped plot regarding associations between serum potassium and CKD. Kaplan-Meier analysis demonstrated significantly lower long-term survival rates in IgG4-RD patients with kidney function at CKD stages 4-5. Cox regression revealed declined kidney functions (G4 HR 6.537 (95% CI: 1.134-37.675)) associated with increased all-cause mortality in IgG4-RD patients. A nomogram was constructed to predict CKD in IgG4-RD promptly with a discrimination (C-index) of 0.846.

CONCLUSIONS

CKD in IgG4-RD was associated with poor outcomes and electrolyte disturbances. Patients with IgG4-RD should be aware of possible deterioration in kidney function. The nomogram proposed would help to identify the subtle possibility of CKD in IgG4-RD. Key points • IgG4-related diseases with deteriorated kidney function have specific clinical and laboratory characteristics. • It is crucial to recognize and address the negative impact of deteriorating kidney function in IgG4-related diseases to prevent further harm. • The nomogram proposed would help to identify subtle kidney involvement by evaluating the possibility of CKD in IgG4-related diseases.

Pachymeningitis associated with IgG4-related disease and ANCA positivity: Case report and review of the literature

OBJECTIVE

Hypertrophic pachymeningitis is a rare clinical disorder involving localized or diffuse thickening of the dura mater. Considering pachymeningitis is both in the clinical spectrum of IgG4-RD and ANCA vasculitis (specifically granulomatosis with polyangiitis), an overlap syndrome is discussed.

METHODS

We report a case of hypertrophic pachymeningitis revealed by headache and cranial nerve dysfunction, and coexistence of biopsy-proven IgG4-RD pachymeningitis and MPO-ANCA positivity. Furthermore, all cases previously reported in the literature of pachymeningitis with IgG4-RD and presence of ANCA were analyzed.

RESULTS

Thirteen patients with pachymeningitis, IgG4-RD and ANCA were analyzed. Patients with HP-related IgG4 and ANCA are mainly male (8, 62%). Median age at diagnosis was 64 years. Main clinical manifestations at diagnosis were localized to the head and neck with headaches (10, 77%), cranial nerve dysfunction (7, 54%), hearing impairment (6, 46%) and vertigo (4, 31%). Except 1 patient with diffuse aortitis, no other systemic manifestation was observed at diagnosis and during follow-up. Serum IgG4 was often elevated (11, 85%) and ANCA was mainly with myeloperoxidase specificity (11, 85%). Seven patients had cerebrospinal fluid analyse with lymphocytic pleocytosis in 5 cases (71%), elevated proteins in 4 cases (57%), positive oligoclonal bands in 3 cases (42%) and decreased glucose in one case (14%). On the MRI, the thickening of the dura mater concerned most often the posterior fossa, in 7 cases (54%). Among 10 cases with histological findings, all showed increased IgG4-positivity of plasma cells, 50% lymphocytic infiltrate but none presented the three major histological criteria of IgG4-related disease. Three (30%) showed histological signs of vasculitis with vascular wall damage and/or giant cells. Among the 12 patients treated with steroid therapy, a clinical improvement was noted in 11 cases (92%). Relapse occurred during tapering in 4 patients (33%). An immunosuppressive drug was added in 2nd line for 7 cases (54%), with a clinical improvement in all.

CONCLUSION

Pachymeningitis with IgG4 and ANCA seems a localized disease to the head and neck. Leptomeningeal biopsy commonly found IgG4 criteria and no vasculitis. All patients responded well to steroid therapy and immunosuppressive drugs, especially rituximab, with clinical and radiological improvement but relapse and/or sequelae are not uncommon.

IgG4-related hypertrophic pachymeningitis with ANCA-positivity: A case series report and literature review

Background

Hypertrophic pachymeningitis (HP) is a rare inflammatory disorder characterized by local or diffuse thickening of the intracranial or spinal dura mater. The most frequent cause of HP is antineutrophil cytoplasmic antibodies (ANCA), followed by IgG4. However, few cases of IgG4-HP coexpressing ANCA have been reported. Herein, we present three cases of IgG4-HP coexpressing ANCA and review the relevant literature to document the overlap of these two HP causes as a potential clinical pattern.

Methods

We retrospectively analyzed three patients with IgG4-HP coexpressing ANCA in our center and consulted the PubMed database to find other relevant cases reported in English from 1976 to April 2022. We used the following keywords: pachymeningitis, meningitis, dura, antineutrophil cytoplasmic antibody, myeloperoxidase, and proteinase-3. We analyzed the clinical, serological, radiological, and pathological characteristics of the obtained cases based on the ACR and Chapel Hill criteria and the exponential moving average (EMA) algorism for ANCA-associated vasculitis (AAV) and the IgG4-RD Comprehensive Diagnostic Criteria.

Results

We analyzed a total of 10 cases: seven literature reports and our three patients (52- and 61-year-old women and a 65-year-old man). The IgG4-related disease (IgG4-RD) diagnoses were definitive in four cases, and probable and possible in three cases. Eight patients had ANCA against myeloperoxidase (MPO), and two had ANCA against proteinase-3 (PR3). Two patients had both IgG4-RD and AAV, while the others only had ANCA seropositivity without additional clinical or pathological markers of AAV.

Conclusion

With regard to HP, we reconfirmed the existence of the IgG4-RD and AAV overlap syndrome. Meanwhile, our review does not support the hypothesis that ANCA positivity in IgG4-RD results from an excessive B-cell response. We speculate that IgG4-RD and AAV have similar or associated pathogeneses, although uncovering the role of IgG4 and ANCA in these pathophysiological processes requires further investigation.

Fatigue in ANCA-associated vasculitis (AAV) and systemic sclerosis (SSc): similarities with Myalgic encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). A critical review of the literature

INTRODUCTION

Persistent debilitating fatigue is a frequent complaint in patients with systemic autoimmune rheumatic diseases (SARDs). Fatigue is, however, frequently overlooked in the clinic, and patients who successfully achieve remission of their disease, often still have a lowered quality of life due to its persistence. How similar is this fatigue to Myalgic encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), what is this fatigue associated with, and what tools/approaches (if any), have resulted in the improvement of fatigue in these patients is poorly defined.

AREAS COVERED

Similarities between the pathophysiology of ME/CFS, systemic sclerosis (SSc) and primary systemic vasculitides (PSV) are discussed, followed by an in-depth review of the prevalence and correlates of fatigue in these diseases. The authors reviewed literature from MEDLINE, APA PsycInfo, Embase, and CINAHL.

EXPERT OPINION

Persistent fatigue is a prominent feature in SARDs and may not be associated with components commonly associated with disease activity and/or progression. Immune and metabolic commonalities exist between ME/CFS, SSc, and PSVs - suggesting that common pathways inherent to the diseases and fatigue may be present. We suggest that patients with features of ME/CFS need to be identified by treating physicians, as they may require alternative approaches to therapy to improve their quality of life.

ANCA-associated vasculitis and IgG4-related disease overlap syndrome: a case report and literature review

Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitides are infrequent autoimmune diseases characterized by inflammation of the walls of small vessels leading to tissue and endothelial damage. On the other hand, IgG4-related disease is a fibroinflammatory disease characterized histologically by lymphoplasmacytic infiltrates with IgG4+ plasma cells, storiform fibrosis, and obliterative phlebitis that may affect nearly every organ of the body. There are similarities in clinical, serological, radiological, and histopathological features between both diseases, and hence, they usually mimic each other complicating the differential diagnosis. Furthermore, reports of patients with the coexistence of both conditions (overlap syndrome) have been reported. We herein report a patient with an unequivocal diagnosis of ANCA-associated vasculitis, specifically granulomatosis with polyangiitis (posterior uveitis, polyneuropathy, pauci-immune glomerulonephritis with crescent formation and granulomas, and MPO-ANCA positivity) and IgG4-related disease (thoracic aortitis, tubulointerstitial nephritis with prominent IgG4+ plasma cell infiltration, fibrosis, and obliterative arteritis, high levels of serum IgG4, and eosinophilia) overlap syndrome.

Eosinophilic granulomatosis with polyangiitis exhibits T cell activation and IgG4 immune response in the tissue; comparison with IgG4-related disease

Objective

To study the pathophysiological differences of EGPA and IgG₄-related disease (RD) by clarifying their clinical, pathological and immunological features.

Methods

Clinical and pathological findings were compared in patients with EGPA and IgG₄-RD. Peripheral blood mononuclear cells were used for comprehensive flow cytometric analysis.

Results

An elevation of the IgG4 level was found in all EGPA cases, with the accompanying pathological findings of lymphocytic infiltration and fibrosis observed in 30.8% patients, and the elevation of IgG₄/IgG ratio in 61.5% patients. However, actual IgG₄ levels, as well as the degree of the infiltration of IgG₄-positive plasma cells, were still higher in patients with IgG₄-RD than patients with EGPA. Examination by ACR/EULAR classification criteria showed only 13.6% of the EGPA patients met entry criteria, while all of them met the exclusion criteria. In regard to the immunophenotyping, EGPA patients had increases in activated CD4 and CD8 T cells compared with the healthy controls. However, no such similar changes occurred in IgG₄-RD patients. On the other hand, both the EGPA and IgG₄-RD patient groups had correlated increased plasmablasts and Tfh. These results indicate the presence of two axes: namely, the activation of T cells and that of B cells. Both axes are present in EGPA, but the T cell activation axis was not observed in IgG₄-RD.

Conclusions

The elevation of serum IgG₄ as well as pathological IgG₄ infiltration are not specific. Meanwhile, EGPA and IgG4-RD differ in immunological phenotypes, indicating the possible importance of the predominant activation of T cells in the development of vasculitis.

Clinicopathological Patterns and Predictors of the Functional Restoration of Immunoglobulin G4-Related Kidney Disease: A Chinese Single-Center Cohort Study

Background: Immunoglobulin G4-related disease (IgG4-RD) is a systemic immunoreactivity-based fibro-inflammatory disease. Immunoglobulin G4-related kidney disease (IgG4-RKD) is a frequently overlooked diagnosis. This study aimed to describe IgG4-RKD and examine the factors relevant to the renal outcomes of IgG4-RD.

Methods: We studied a prospective IgG4-RKD cohort between January 2012 and December 2020 with close follow-up. Clinicopathologic data at kidney biopsy were collected and analyzed. We aimed to explore independent risk factors for long-term renal outcome and disease relapse. Patients with an eGFR<45 ml/min per 1.73m² at 12 months were defined as having poor outcomes.

Results: The included 42 patients with IgG4-RKD had a mean age of 58.5 ± 8.7 years (male-to-female ratio = 5:1). The IgG4-RD responder index (RI) was 12.2 ± 3.3. A total of 66.7% of the patients presented with acute on kidney disease or acute on chronic kidney disease. Eight patients (19.0%) showed nephrotic-range proteinuria, and nine (21.4%) had high-titer IgG4-autoantibodies, including antineutrophil cytoplasmic antibody and anti-phospholipase A2 receptor. A kidney biopsy was conducted in 40 patients. Thirty-seven (90.0%) patients were diagnosed with IgG4-related tubulointerstitial nephritis, and 19 (47.5%) of them had concurrent glomerular diseases (membranous nephropathy [MN], n = 3; crescentic glomerulonephritis [CrGN], n = 11; diabetic kidney disease, n = 3; and both MN and CrGN, n = 2). IgG4-RD RI had a close relationship with serum C3 (R = −0.509, P = 0.001), C4 (R = −0.314, P = 0.049) levels, and peripheral blood eosinophil count (PBEC; R = 0.377, P = 0.024), factors that were not included in RI scores. Correlation analysis disclosed that IgG4-RD RI (R = 0.422, P = 0.007), organs involved (R = 0.452, P = 0.003), and C3 (R = −0.487, R = 0.002) were correlated with the percentage decrease of serum creatinine at 1 month. However, multivariate regression analysis failed to identify any clinicopathological parameters that could predict short-term renal restoration and IgG4-RKD relapse. Ten out of 29 variables, of most importance, were identified by the least absolute shrinkage and selection operator (LASSO) regression analysis. By multivariate logistic regression a higher serum IgG4 (OR = 0.671, P = 0.010), IgG1 (OR = 1.396, P = 0.049), IgG3 (OR = 19.154, P = 0.039), and erythrocyte sedimentation rate (ESR; OR = 1.042, P = 0.032) were found to be independent factors for poor long-term outcome. Conventional immunosuppressive medications and/or rituximab were prescribed, and in 83.3% of the patients, the kidney function improved. Repeat kidney biopsies confirmed the remission of interstitial inflammation in two patients under immunosuppressive therapy. However, the disease relapse rate was as high as 31.0%.

Conclusions: We strongly recommend a kidney biopsy in active IgG4-RD, especially when there is proteinuria and renal dysfunction, because concurrent glomerular involvement and active interstitial inflammation should be assessed. A higher serum IgG1, IgG3, and ESR were independent factors for the poor long-term renal outcome; however, elevated IgG4 predicted a good renal prognosis, and appropriate and timely immunosuppressive therapy can help achieve a better prognosis.

Time-related variation in IgG subclass concentrations in a group of healthy Danish adults

Introduction

Immunoglobulin G subclass measurements are important for the diagnostic work‐up of immunodeficiencies and immunoglobulin G4 (IgG4) related diseases. It is currently unknown whether a single sampling is truly representative for an individual's IgG subclass concentrations. This study aimed to investigate whether IgG and IgG subclass concentrations in healthy individuals are stable over time.

Method

With a span of median 42 weeks, four samples from each of 54 (34M, 20F) healthy adult volunteers (24–66 years) were analyzed for IgG and IgG1–4 using turbidimetry. Concentrations were compared within and between individuals.

Results

IgG and IgG subclass concentrations followed either a normal (IgG, IgG1, and IgG3) or log normal (IgG2 and IgG4) distribution. Immunoglobulin 4 demonstrated by far the widest range of concentrations between individuals (670‐fold: 0.004–2.68 g/L). Immunoglobulin G subclass variations within individuals were expressed as pooled standard deviations (PSD). These ranged from 0.056 (IgG4) to 0.955 g/L (IgG) and correlated with mean concentration of IgG or the particular IgG subclass. As a consequence, the relative PSDs (i.e., PSD divided by mean IgG or IgG subclass concentration) fell within a narrow range: 5.82%–10.1%. Based on these numbers, the 95%‐upper one‐sided confidence limits for intraindividual IgG and IgG subclass variation was calculated to range from 9.82% (IgG2) to 16.9% (IgG4).

Conclusion

The study documents that IgG or IgG subclass concentrations within healthy individuals are very stable over at least 42 weeks. The expected variation for IgG4 concentrations at a 95% confidence level does not exceed ±16.9%.

IgG4-related disease and ANCA positive vasculitis in childhood: a case-based review

Autoimmune pancreatitis (AIP) type 1 is an IgG4-related disease (IgG4-RD), characterized by inflammatory pseudotumors and histologically by dense lymphoplasmacytic infiltrates rich in IgG4 positive plasma cells, storiform fibrosis, and obliterative phlebitis. Although quite rare, IgG4-RD was found to be associated with medium or small vessel vasculitides. A new overlap syndrome between IgG4-RD and ANCA-associated vasculitis (AAV) has recently been described in the adult population. Here we present a 16-year-old adolescent girl admitted with abdominal pain, episcleritis, palpable purpura, salivary gland enlargement, and bloody diarrhea. Laboratory investigations revealed findings of glomerulonephritis. Abdominal imaging surprisingly revealed a focal mass in the pancreatic tail, while the c-ANCA level was found to be quite high as well as serum IgG4 level. Biopsy of the pancreatic mass showed lymphoplasmacytic IgG4 positive cells infiltrating the pancreas with storiform fibrosis compatible with IgG4-related AIP. The renal biopsy that was done simultaneously showed necrotizing granulomatous vasculitis indicating AAV. Renal biopsy showed IgG4 positive plasma cells very rarely by immunohistochemical examination, which does not indicate any significance for IgG4-RD. Our diagnosis was IgG4-related AIP and AAV overlap syndrome, which has not been reported in the pediatric populations yet. IgG4-RD should be investigated in patients with ANCA-associated vasculitis who shows atypical organ involvement. We searched the Pubmed/Medline and Google Scholar databases to identify clinical findings, treatment, and outcome of the patients with IgG4-related AIP and AAV.

A case with overlapping features of IgG4-related autoimmune pancreatitis, Sjögren's syndrome and anti-aminoacyl-tRNA synthetase syndrome

A 55-year-old man who had been diagnosed with autoimmune pancreatitis five years earlier was referred to our department because of finger swelling, finger stiffness and the presence of interstitial lung disease (ILD). The patient was diagnosed with Sjögren's syndrome according to the pathological findings of minor salivary glands and positive anti-SS-A antibodies. Later, at age 58, he was hospitalised due to the exacerbation of the ILD. Serum IgG4 level was checked and was found to be elevated (417 mg/dL). After the introduction of cyclosporine in addition to the prednisolone, at age 60, the ILD disease activity stabilised. However, at age 62, fever, myalgia and mechanic's hands appeared. His serum creatine kinase level was high, and magnetic resonance imaging showed inflammatory findings of muscle. In-house ELISA clarified that his serum carried anti-PL-7 antibody among anti-aminoacyl-tRNA synthetase antibodies. This is a unique case who had overlapping features of IgG4-related autoimmune pancreatitis, Sjögren's syndrome and anti-synthetase syndrome. Although the aetiology of the complications in this patient is obscure, autoimmunity might have played a significant role in the disease conditions and prognosis of the present case with IgG4-related disease.

Simultaneous presentation of granulomatosis with polyangiitis (GPA) and immunoglobulin G4-related disease (IgG4-RD). Leaving an open question: widening the spectrum of a single disease or real overlap?

Because of a similar organ involvement and histopathological features, IgG4-related disease (IgG4-RD) may mimic some forms of granulomatosis with polyangiitis (GPA). However, several cases of clear coexistence or overlap of both diseases have been reported. We describe a case of a 47-year-old man presenting with a renal mass and a nasal crusting showing histopathological features of IgG4-RD in both territories. Cytoplasmic/proteinase 3 (PR3) antineutrophil cytoplasmic antibodies (ANCA) were positive and the patient subsequently developed kidney failure and nephritic syndrome that led to a renal biopsy re-evaluation revealing changes compatible with segmental necrotising glomerulonephritis and GPA. Remission induction therapy with prednisone and rituximab was started and clinical and laboratory parameters returned to normal. After administering a maintenance regimen based in rituximab 500 mg every six month the patient remained asymptomatic during 4 years of follow-up and free of prednisone the last 18 months. Although coexistence or overlap of GPA and IgG4-RD may be established in some clinical scenarios, the possibility of widening the spectrum of a single disease is also postulated.

Steroid Therapy and Steroid Response in Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP), a unique subtype of pancreatitis, is often accompanied by systemic inflammatory disorders. AIP is classified into two distinct subtypes on the basis of the histological subtype: immunoglobulin G4 (IgG4)-related lymphoplasmacytic sclerosing pancreatitis (type 1) and idiopathic duct-centric pancreatitis (type 2). Type 1 AIP is often accompanied by systemic lesions, biliary strictures, hepatic inflammatory pseudotumors, interstitial pneumonia and nephritis, dacryoadenitis, and sialadenitis. Type 2 AIP is associated with inflammatory bowel diseases in approximately 30% of cases. Standard therapy for AIP is oral corticosteroid administration. Steroid treatment is generally indicated for symptomatic cases and is exceptionally applied for cases with diagnostic difficulty (diagnostic steroid trial) after a negative workup for malignancy. More than 90% of patients respond to steroid treatment within 1 month, and most within 2 weeks. The steroid response can be confirmed on clinical images (computed tomography, ultrasonography, endoscopic ultrasonography, magnetic resonance imaging, and ¹⁸F-fluorodeoxyglucose-positron emission tomography). Hence, the steroid response is included as an optional diagnostic item of AIP. Steroid treatment results in normalization of serological markers, including IgG4. Short- and long-term corticosteroid treatment may induce adverse events, including chronic glycometabolism, obesity, an immunocompromised status against infection, cataracts, glaucoma, osteoporosis, and myopathy. AIP is common in old age and is often associated with diabetes mellitus (33-78%). Thus, there is an argument for corticosteroid therapy in diabetes patients with no symptoms. With low-dose steroid treatment or treatment withdrawal, there is a high incidence of AIP recurrence (24-52%). Therefore, there is a need for long-term steroid maintenance therapy and/or steroid-sparing agents (immunomodulators and rituximab). Corticosteroids play a critical role in the diagnosis and treatment of AIP.