Comparison of the efficacy of first­/second­generation EGFR­tyrosine kinase inhibitors and osimertinib for EGFR­mutant lung cancer with negative or low PD­L1 expression.

In epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) with negative or low programmed death ligand-1 (PD-L1) expression, the acquisition rate of the T790M mutation is higher after treatment with first-/second-generation EGFR-tyrosine kinase inhibitors (TKIs) and the progression-free survival (PFS) is longer in patients treated with osimertinib. The present study compared the clinical course after the initiation of each EGFR-TKI monotherapy in patients with EGFR-mutant NSCLC with negative or low PD-L1 expression. Data of patients with EGFR-mutant NSCLC with negative or low PD-L1 expression who were treated with EGFR-TKI monotherapy were retrieved and retrospectively analyzed. Between June 2013 and November 2023, 26 and 29 patients were treated with first-/second-generation EGFR-TKIs and osimertinib, respectively. The PFS time was longer in patients treated with osimertinib (median, 22.5 months) than in those treated with first-/second-generation EGFR-TKIs (median, 12.9 months). However, the EGFR-TKI treatment duration, defined as the PFS for osimertinib, or the sum of the PFS for first-/second-generation EGFR-TKIs and sequential osimertinib therapy after the acquisition of the T790M mutation, was similar between patients treated with first-/second-generation EGFR-TKIs (median, 23.0 months) and osimertinib (median, 22.5 months). The Cox proportional hazard model suggested that there was no significant difference in the EGFR-TKI treatment duration between patients treated with first-/second-generation EGFR-TKIs and patients treated with osimertinib (hazard ratio, 1.31, 95% CI, 0.55-3.13). In conclusion, first-/second-generation EGFR-TKIs and osimertinib were associated with a similar EGFR-TKI treatment duration in patients with EGFR-mutant NSCLC with negative or low PD-L1 expression. The findings suggested that both treatments are promising for this population.

Immune Checkpoint Inhibitor Therapy for Patients With Non-small Cell Lung Cancer Ineligible for Platinum Doublet Chemotherapy.

BACKGROUND/AIM: Combined therapy with immune checkpoint inhibitors plus platinum doublet chemotherapy has a survival advantage over platinum doublet chemotherapy in patients with non-small cell lung cancer. However, a variety of factors make it difficult to administer treatment with platinum doublet chemotherapy in many patients in clinical practice and there are few reports on the efficacy and safety of first-line treatments with immune checkpoint inhibitors for patients who are ineligible for platinum doublet chemotherapy. This observational study aimed to evaluate the efficacy and safety of first-line immune checkpoint inhibitor therapy for this population. PATIENTS AND METHODS: We retrospectively assessed the survival and adverse events from the initiation of first-line immune checkpoint inhibitor therapy, including pembrolizumab or nivolumab plus ipilimumab in patients with non-small cell lung cancer who were ineligible for platinum doublet chemotherapy. RESULTS: Data from 48 patients were analyzed. Seventeen patients showed a performance status (PS) of ≥2 while 16 and 15 patients were considered ineligible for platinum doublet chemotherapy because of age and comorbidities, respectively. The median (95% confidential interval, CI) progression-free survival (PFS) and overall survival (OS) of the 48 patients were 7.1 (1.7-13.7) and 31.7 (8.8-not estimated) months, respectively. The two-year PFS and OS rates (95% CI) were 30.8% (18.2%-47.2%) and 50.7% (33.7%-67.7%), respectively. In patients with a PS of ≥2, the median (95% CI) PFS and OS were 1.6 (1.2-not estimated) and 5.5 (2.3-not estimated) months, respectively. The two-year PFS and OS rates (95% CI) were 34.3% (15.8%-59.2%) and 45.3% (22.2%-70.7%), respectively. CONCLUSION: Patients with non-small cell lung cancer and a PS of 0-1 who were ineligible for platinum doublet chemotherapy had favorable outcome after the initiation of ICI therapy, and even in patients with a PS of ≥2, they achieved high two-year PFS and OS rates.

Improved Renal Function in Initial Treatment Improves Patient Survival, Renal Outcomes, and Glucocorticoid-Related Complications in IgG4-Related Kidney Disease in Japan.

Introduction: We aimed to clarify long-term renal prognosis, complications of malignancy, glucocorticoid (GC) toxicity, and mortality in immunoglobulin G4 (IgG4)-related kidney disease (IgG4-RKD). Methods: Reviewing the medical records of 95 patients with IgG4-RKD, we investigated clinical and pathologic features at baseline, the course of renal function, complications of malignancy, GC toxicity, and mortality during follow-up (median 71 months). The standardized incidence ratio (SIR) of malignancy and standardized mortality ratio were calculated using national statistics. Factors related to outcomes were assessed by Cox regression analyses. Results: At diagnosis, the median estimated glomerular infiltration rate (eGFR) was 46 ml/min per 1.73 m2. GC achieved initial improvement. Additional renal function recovery within 3-months of initial treatment occurred in patients with highly elevated serum IgG and IgG4 levels and hypocomplementemia. During follow-up, 68%, 17%, and 3% of the patients had chronic kidney disease (CKD), >30% eGFR decline, and end-stage renal disease (ESRD), respectively. Age-adjusted and sex-adjusted Cox regression analyses indicated that eGFR (hazard ratio [HR], 0.71) and extensive fibrosis (HR, 2.58) at treatment initiation had a significant impact on the time to CKD. Ten patients died, and the standardized mortality ratio was 0.94. The SIR of malignancy was 1.52. The incidence rate (IR) of severe infection was 1.80/100 person-years. Cox regression analyses showed that the best eGFR within 3 months after treatment initiation were associated with lower mortality (HR 0.67) and fewer severe infections (HR 0.63). Conclusion: This study suggests that more renal function recovery through early treatment initiation may improve patient survival, renal outcomes, and some GC-related complications in IgG4-RKD.

The 2022 revised diagnostic criteria for IgG4-related respiratory diseases.

In 2011, the Comprehensive Diagnostic Criteria for IgG4-related disease was published in Japan. Organ-specific diagnostic criteria based on organ-specific findings were proposed and published by each of the related societies, and the diagnostic criteria for IgG4-related respiratory disease was published in 2015. Based on the revisions to the comprehensive diagnostic criteria in 2020 and the publication of the Classification Criteria, new diagnostic criteria for IgG4-related respiratory disease are presented. Emphasis has been placed on evaluating specific pathological findings and excluding other respiratory diseases. It is mentioned in the commentary that in cases with imaging findings suggestive of interstitial pneumonia with chronic fibrosis or poor response to steroid therapy, other possible diseases should be considered.

Metachronous bilateral immunoglobulin G4-related pleuritis: A case report and literature review.

Immunoglobulin G4-related disease (IgG4-RD) is a newly recognized disease, and therefore its clinical features are not yet fully understood. Here, we describe a surgical case of metachronous bilateral IgG4-related pleuritis and postoperative chylothorax. This case could provide key insights into the pathology of IgG4-RD from a surgical perspective. We present a 70-year-old woman who had a right pleural mass. Video-assisted thoracoscopic pleural mass resection was performed, and the patient was diagnosed with right-sided IgG4-related pleuritis. Two years later, she was also diagnosed with left-sided IgG4-related pleuritis. We suspected the presence of IgG4-positive plasma cell infiltration. Additionally, she experienced a complicated postoperative chylothorax on the left side. It is important to consider the altered course of lymphatic vessels when extensively removing the pleura near the right thoracic duct. The occurrence of metachronous bilateral IgG4-associated pleuritis has not been previously reported, making this case particularly significant for understanding the pathology of IgG4-RD from a surgical standpoint.

Peripheral CD4 memory T cells predict the efficacy of immune checkpoint inhibitor therapy in patients with non-small cell lung cancer.

Immune checkpoint inhibitors have significantly improved the prognosis in patients with non-small cell lung cancer, compared with cytotoxic agents. However, the prediction of treatment response is often difficult, even after assessing the tumor programmed death-ligand 1 expression. We conducted this observational study to analyze the association between the differentiation of peripheral CD4 + T cells and the efficacy of immune checkpoint inhibitor therapy. We enrolled patients who were diagnosed with non-small cell lung cancer and received immune checkpoint inhibitor therapy between 2020 and 2022. Blood samples were collected at the start of immune checkpoint inhibitor therapy, and the expressions of PD-1, CCR7, and CD45RA in peripheral CD4 + T cells were analyzed by flow cytometry. The association between the findings of flow cytometry and survival after the initiation of the immune checkpoint inhibitor therapy was evaluated. Forty patients with non-small cell lung cancer were enrolled. The Cox proportional hazards model showed that an increased proportion of CD45RA-CD4 + T cells was associated with a reduced risk of progression after adjustment for performance status, tumor programmed death-ligand 1 expression level, mutation status of the epidermal growth factor receptor gene, and combined therapy with cytotoxic agents. The present study showed that the proportion of peripheral CD45RA- CD4 + T cells was associated with progression-free survival after the initiation of immune checkpoint inhibitor therapy, independent of several clinical factors.

Association Between the Severity of Immune-related Adverse Events and the Prognosis in Patients With Non-small Cell Lung Cancer Receiving Treatment With Immune Checkpoint Inhibitors.

BACKGROUND/AIM: Among patients with non-small cell lung cancer (NSCLC) treated with immune checkpoint inhibitors (ICI), survival is reported to be longer in those experiencing immune-related adverse events (irAEs). We evaluated the progression-free survival (PFS) in the absence of further treatment after ICI therapy was discontinued because of the emergence of irAEs in patients with NSCLC. PATIENTS AND METHODS: Data from patients with NSCLC in whom ICI therapy was discontinued because of the development of irAEs were retrospectively analyzed. The primary endpoint was the PFS from the last day of administration of ICIs, in the absence of any further treatment. RESULTS: A total of 162 patients with NSCLC received treatment with ICIs between January 2016 and December 2021. Among them, ICI therapy was discontinued in 33 patients because of the appearance of irAEs. The median (95% confidence interval) PFS in the absence of any treatment after the last administration of ICIs was 7.2 (4.2-12.3) months. According to the Common Terminology Criteria for Adverse Events, the Cox proportional hazards model was used to identify the severity of irAEs, which were determined to be significantly associated with the PFS in the absence of any further treatment after the last administration of ICI therapy. CONCLUSION: Although the present study showed that the PFS in patients with NSCLC was relatively long in the absence of any further treatment after the last administration of ICIs, the PFS was associated with the severity of the irAEs, and some patients showed early disease progression or death.

Associations of immune checkpoint inhibitor therapy efficacy with clinical parameters and tumor­infiltrating CD68­positive cell counts in patients with EGFR­mutant non­small cell lung cancer.

Immune checkpoint inhibitor (ICI) therapy has been less effective in patients with non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations than in patients with EGFR wild-type NSCLC. This retrospective study was conducted to investigate the associations of clinical parameters with the efficacy of ICI therapy in patients with EGFR-mutant NSCLC. Clinical information was retrieved from the medical charts, and immunohistochemical analysis was performed in some cases to determine the tumor-infiltrating CD68-positive cell count. Data from 46 patients were included in the analysis. The median (95% confidence interval) progression-free survival and overall survival from the initiation of ICI therapy was 1.4 months (1.0-1.7 months) and 6.4 months (3.9-19.0 months), respectively. Analysis using a Cox proportional hazards model revealed that tumor programmed death-ligand 1 expression was associated with the overall survival of patients with EGFR-mutant NSCLC after ICI treatment. The tumor-infiltrating CD68-positive cell count was evaluated in 11 patients. Comparison using the log-rank test revealed that the progression-free survival time after ICI treatment was longer in the patients with lower tumor-infiltrating CD68-positive cell counts than those with higher tumor-infiltrating CD68-positive cell counts. The present analysis demonstrated that PD-L1 expression and the tumor-infiltrating CD68-positive cell count may be associated with the efficacy of ICI therapy in patients with NSCLC harboring EGFR mutations.

Efficacy of immune checkpoint inhibitor therapy in patients with pulmonary sarcomatoid carcinoma in clinical practice.

OBJECTIVE: Studies have suggested the potential efficacy of immune checkpoint inhibitors (ICIs) for pulmonary sarcomatoid carcinoma. This multicenter observational study was conducted to evaluate the efficacy of systemic ICI therapy and chemoradiation followed by durvalumab therapy for pulmonary sarcomatoid carcinoma. METHODS: We analyzed the data of patients with pulmonary sarcomatoid carcinoma who received systemic ICI therapy or chemoradiation followed by durvalumab therapy between 2016 and 2022. RESULTS: In this study, data of a total of 22 patients who received systemic ICI therapy and four patients who received chemoradiation followed by durvalumab therapy were analyzed. In the patients who received systemic ICI therapy, the median progression-free survival after initiation of therapy was 9.6 months, and the overall survival did not reach the median. The 1-year progression-free survival rate and overall survival rate were estimated to be 45.5% and 50.1%, respectively. Although the log-rank test revealed no significant association between the tumor expression level of programmed death ligand-1 (tumor proportion score evaluated using 22C3 antibody: ≥50% vs. <50%) and the survival duration, the majority of patients showing long-term survival showed a tumor proportion score of ≥50%. Of four patients treated with chemoradiation followed by durvalumab therapy, two patients showed an overall survival of ≥30 months, whereas the remaining two patients died within 12 months. CONCLUSION: The progression-free survival of patients who received systemic ICI therapy was 9.6 months, suggesting that ICI therapy might be effective in patients with pulmonary sarcomatoid carcinoma.

Recent advances in IgG4-related kidney disease.

Recent advances in the management and understanding of immunoglobulin (Ig)G4-related kidney disease (RKD) have emphasized the importance of urgent treatment in IgG4-related tubulointerstitial nephritis. On the other hand, to avoid long-term glucocorticoid toxicity, strategies for early withdrawal of steroids or combination of immunosuppressants, such as rituximab, and the minimum dose of steroids have been pursued. However, disease recurrence after reducing or stopping steroid therapy hampers early withdrawal of glucocorticoid maintenance therapy. In addition, knowledge has accumulated in diagnostic approaches including differential diagnosis of anti-neutrophil cytoplasmic antibodies-associated vasculitis, idiopathic multicentric Castleman's disease, and Rosai-Dorfman disease with kidney lesion, which leads to earlier and precise diagnosis of IgG4-RKD. This review summarizes recent progress in the differential diagnosis of IgG4-RKD and related treatment strategies and recent topics of hypocomplementaemia, membranous glomerulonephritis, and IgG4-related pyelitis and periureteral lesion.

Respiratory lesions in IgG4-related disease: classification using 2019 American College of Rheumatology/European League Against Rheumatism criteria.

In this study, ILDs involving IgG4-positive plasma cell infiltration were classified using the 2019 ACR/EULAR criteria. Most IgG4-positive interstitial pneumonia cases were excluded, suggesting the need for a unique treatment strategy. https://bit.ly/38GiUJM.

Association of Tumor PD-L1 Expression With Time on Treatment Using EGFR-TKIs in Patients With EGFR-Mutant Non-small Cell Lung Cancer.

BACKGROUND/AIM: The association between tumor PD-L1 expression and the rate of acquisition of the T790M mutation during treatment with first-/second-generation epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) is a matter of study. This retrospective study was conducted to evaluate the association of tumor PD-L1 expression with the time on treatment under EGFR-TKIs in patients with EGFR-mutant non-small cell lung cancer (NSCLC), treated with first-/second-generation EGFR-TKIs. PATIENTS AND METHODS: We conducted a retrospective review of the medical charts of patients with EGFR-mutant NSCLC treated with first- /second-generation EGFR-TKIs. Time on treatment with EGFR-TKIs was defined as the sum of progression-free survival period (PFS) from the start of treatment with first- /second-generation EGFR-TKIs and the PFS from the start of osimertinib treatment after acquisition of the T790M mutation. Tumor PD-L1 expression was evaluated using the 22C3 antibody. RESULTS: Data of a total of 49 patients were analyzed, including 20 patients with negative tumor PD-L1 expression (tumor proportion score <1%) and 29 patients with positive tumor PD-L1 expression (tumor proportion score ≥1%). In the negative tumor PD-L1 expression group, the T790M mutation was detected in 12 (75%) of the 16 patients. In the positive tumor PD-L1 expression group, the T790M mutation was detected 6 (31.6%) out of the 19 patients in whom it was tested. The median (95% confidence interval) time on treatment with EGFR-TKIs was 21.7 (12.9-24.8) months and 12.3 (5.6-22.2) months in the negative and positive tumor PD-L1 expression groups, respectively. Analysis using a Cox proportional hazards model identified performance status and presence/absence of tumor PD-L1 expression as significantly associated with the time on treatment with EGFR-TKIs. CONCLUSION: EGFR-mutant NSCLC patients with negative tumor PD-L1 expression showed a higher rate of acquisition of the T790M mutation and implementation rate of osimertinib therapy, leading to a longer time on treatment with EGFR-TKI.

Fish diversity of a spring field in Hopong Town, Taunggyi District, Shan State, Myanmar (the Salween River Basin), with genetic comparisons to some "species endemic to Inle Lake".

Hopong, a small town in the Salween (Thanlwin) River Basin, Myanmar, is located 35 km northeast of Inle Lake, a famous ancient lake with numerous endemic fish species. We surveyed the fish fauna of a spring pond in Hopong in 2016, 2019 and 2020 and identified 25 species. Of these, seven, including Inlecyprisauropurpureus and Sawbwaresplendens, had been considered endemic to Inle Lake and at least three species were genetically unique. Eight were suspected or definite introduced species, including Oreochromisniloticus and Gambusiaaffinis. We were unable to identify a nemacheilid species of the genus Petruichthys, which would need a taxonomic examination. The Hopong area is being developed rapidly and, hence, it is crucial to conserve its native fish species and the freshwater ecosystems.

Irinotecan monotherapy as third- or further-line treatment for patients with small cell lung cancer.

BACKGROUND: Small cell lung cancer (SCLC) is a very aggressive cancer and recurrence is inevitable. Treatment of recurrent disease is important for improving the prognosis of patients with SCLC. METHODS: We conducted a retrospective observational study to investigate the efficacy and safety of irinotecan monotherapy as third- or further-line treatment in patients with SCLC. RESULTS: Data of 15 patients who had received irinotecan monotherapy as third- or further-line treatment between 2004 and 2019 were analyzed. The median progression-free survival duration (95% confidence interval) from the initiation of treatment with irinotecan was 2.7 (1.4-3.8) months, and the median overall survival duration (95% confidence interval) from the initiation of irinotecan treatment was 10.0 (3.9-12.9) months. Partial response, stable disease or non-complete response/non-progressive disease, and progressive disease were observed in 1, 6, and 8 patients, respectively. Adverse events ⩾ grade 3 in severity were observed in 2/2 (100%) patients who were homozygous for UGT1A1 mutation, 2/3 (66.7%) patients who were heterozygous for UGT1A1 mutation, 4/6 (66.7%) patients who had wild-type UGT1A1, and 2/4 (50.0%) patients in whom the UGT1A1 mutation status was unknown. CONCLUSION: Our results suggest that irinotecan monotherapy can be a useful alternative treatment option in the third-line setting for patients with SCLC.

Clinical characteristics of immunoglobulin G4-positive interstitial pneumonia.

This study suggests that IgG4 + IP with abundant IgG4 + cells and elevated serum IgG4 levels could be treated differently from IgG4-related respiratory disease due to potential differences in disease behaviour and response to corticosteroid therapy https://bit.ly/3dUo2cu.

Case Series of Pleomorphic Carcinoma of the Lung Treated With Immune Checkpoint Inhibitors.

AIM: We report, herein, three cases of pleomorphic carcinoma of the lung treated with immune checkpoint inhibitors. Case 1: A 73-year-old man was diagnosed as having pleomorphic carcinoma of the lung and treated with pembrolizumab alone. However, he showed no response and died 4 months after the initiation of the treatment. Case 2: A 66-year-old man was diagnosed as having pleomorphic carcinoma of the lung. He was started on a combination regimen of pembrolizumab plus carboplatin plus nab-paclitaxel, and a remarkable response was observed. Case 3: A 49-year-old man was diagnosed as having pleomorphic carcinoma of the lung. He was started on pembrolizumab monotherapy as second-line treatment. Eleven months after the treatment initiation, computed tomography revealed the decrease of tumor diameter. CONCLUSION: Immune checkpoint inhibitor therapy is expected to improve the prognosis of patients with pleomorphic carcinoma of the lung.

The pronounced lung lesions developing in LATY136F knock-in mice mimic human IgG4-related lung disease.

RATIONALE: Immunoglobulin (Ig) G4-related disease (IgG4-RD) is a novel clinical disease entity characterized by an elevated serum IgG4 concentration and tumefaction or tissue infiltration by IgG4-positive plasma cells. Pathological changes are most frequently seen in the pancreas, lacrimal glands, and salivary glands, but pathological changes in the lung also exist. Linker for activation of T cell (LAT)Y136F knock-in mice show Th2-dominant immunoreactions with elevated serum IgG1 levels, corresponding to human IgG4. We have reported that LATY136F knock-in mice display several characteristic features of IgG4-RD and concluded that they constitute an appropriate model of human IgG4-RD in salivary glands, pancreas, and kidney lesions. OBJECTIVES: The aim of this study is to evaluate whether lung lesions in LATY136F knock-in mice can be a model of IgG4-related lung disease. METHODS: Lung tissue samples from LATY136F knock-in mice (LAT) and wild-type mice (WT) were immunostained for IgG1 and obtained for pathological evaluation, and cell fractions and cytokine levels in broncho-alveolar lavage fluid (BALF) were analyzed. RESULTS: In the LAT group, IgG1-positive inflammatory cells increased starting at 4 weeks of age and peaked at 10 weeks of age. The total cell count and percentage of lymphocytes increased significantly in BALF in the LAT group compared to the WT group. In BALF, Th2-dominant cytokines and transforming growth factor-ß were also increased. In the LAT group, marked inflammation around broncho-vascular bundles peaked at 10 weeks of age. After 10 weeks, fibrosis around broncho-vascular bundles and bronchiectasis were observed in LATY136F knock-in mice but not WT mice. CONCLUSIONS: LATY136F knock-in mice constitute an appropriate model of lung lesions in IgG4-RD.

The 2020 revised comprehensive diagnostic (RCD) criteria for IgG4-RD.

IgG4-related disease (IgG4-RD) is a fascinating clinical entity first reported in this century in Japan, and includes a wide variety of diseases, such as formerly named Mikulicz's disease (MD), autoimmune pancreatitis (AIP), interstitial nephritis, prostatitis and retroperitoneal fibrosis. The Japanese IgG4 team organized by the Ministry of Health, Labor and Welfare (MHLW) of Japan has published the first criteria, comprehensive diagnostic (CD) criteria for IgG-RD 2011. Thereafter, IgG4-RD has been accepted widely and many cases have been reported from all over the world. Several problems have arisen in clinical practice, however, including the difficulty obtaining biopsy samples, and the sensitivity and specificity in cut off level of serum IgG4 and impaired immunostaining of IgG4. Given these situations, the Japanese IgG4 team has updated the 2011 comprehensive diagnostic criteria for IgG4-RD and propose the 2020 revised comprehensive diagnostic (RCD) criteria for IgG4-RD, which consists of 3 domains; 1) Clinical and radiological features, 2) Serological diagnosis and 3) Pathological diagnosis. In addition, the new pathological diagnosis is composed by three sub-items including storiform fibrosis and obliterative phlebitis.

Phenotyping of IgG4-related diseases based on affected organ pattern: A multicenter cohort study using cluster analysis.

OBJECTIVES: Immunoglobulin G4-related disease (IgG4-RD) is a systemic, multiorgan disease of unknown etiology. We aimed to classify IgG4-RD by a combination pattern of affected organs and identify the clinical features, including the comorbidities of each subgroup. METHODS: Patients diagnosed with IgG4-RD between April 1996 and June 2018 were enrolled from three institutes. Hierarchical cluster analysis was performed using six frequently affected organs (lacrimal gland and/or orbit, salivary gland, lung, pancreas, kidney, and retroperitone and/or aorta). Clinical features, such as comorbidities and outcomes, were compared between clusters. RESULTS: In total, 108 patients enrolled in this cohort could be stratified into five distinct subgroups: group 1, lung dominant group; group 2, retroperitoneal fibrosis and/or aortitis dominant group; group 3, salivary glands limited group; group 4, Mikulicz's disease dominant group; and group 5, autoimmune pancreatitis with systemic involvement group. There were significant between-group differences in sex (male dominant in group 1, 2, and 5), history of asthma and allergies on the respiratory tract (most frequent in group 5), and malignancy (most frequent in group 5). CONCLUSION: IgG4-RD can be classified into subgroups according to the pattern of affected organs. Group 5 may have frequent complications with allergies and malignancies.

Hypocomplementemia is related to elevated serum levels of IgG subclasses other than IgG4 in IgG4-related kidney disease.

OBJECTIVES: This study investigated the clinical features of IgG4-RKD patients with hypocomplementemia compared with those without it, so as to clarify the factors related to hypocomplementemia. METHODS: In this single-center retrospective study, we analyzed the clinical features of 25 patients with IgG4-RKD according to the presence/absence of hypocomplementemia. Additionally, we validated the results of a single-center study in a separate large multicenter cohort of 328 patients with IgG4-RD, and searched for factors related to hypocomplementemia. RESULTS: Serum IgG levels (p < .001), non-IgG4 IgG levels, calculated as the total IgG minus IgG4 (p < .001), serum IgG1 levels (p = .017), and the number of involved organs (p = .018) were significantly higher in the hypocomplementemia group. At relapse of renal lesions in four patients, all had serum IgG4 re-elevation, with the three with hypocomplementemia presenting worsening of hypocomplementemia and re-elevation of non-IgG4 IgG levels. In a validation cohort of 328 patients with IgG4-RD, multivariate logistic regression analysis indicated elevation of non-IgG4 IgG levels to be an independent factor related to hypocomplementemia in the patients with IgG4-RKD. CONCLUSION: The present study suggests that hypocomplementemia is associated with elevation of IgG subclasses other than IgG4 including IgG1 in IgG4-RKD.