Expanded CD4+CXCR5-PD-1+ peripheral T helper like cells and clinical significance in IgG4-related disease.

To identify the phenotypic features and clinical significance of peripheral T helper (Tph) like cells in IgG4-RD, 54 untreated IgG4-RD patients and 57 healthy controls (HCs) were enrolled. Flow cytometry analysis, ELISA and correlation analysis were performed. Results indicated that percentages of CD4 + CXCR5-PD-1+ Tph like cells in the peripheral blood of IgG4-RD patients were significantly higher than those of HCs (2.27% ± 1.99% vs 1.12% ± 0.98%, P < 0.001). Expression of CD38, CD25, and TIGIT was higher, whereas that of CCR7, CD127 was lower in the Tph like cells from the IgG4-RD patients than in those from the HCs. The IgG4-RD patients with affected internal organs had higher circulating Tph like cell levels than those without (2.69% ±1.99% vs 1.23% ± 0.93%, respectively, P = 0.003). In addition, Tph like cells correlated with serum IgG and IgG4 and peripheral plasmablast levels which could be a promising biomarker for disease activity monitoring.

Transcriptional regulation and small compound targeting of ACE2 in lung epithelial cells.

Angiotensin-converting enzyme 2 (ACE2) is the receptor of COVID-19 pathogen SARS-CoV-2, but the transcription factors (TFs) that regulate the expression of the gene encoding ACE2 (ACE2) have not been systematically dissected. In this study we evaluated TFs that control ACE2 expression, and screened for small molecule compounds that could modulate ACE2 expression to block SARS-CoV-2 from entry into lung epithelial cells. By searching the online datasets we found that 24 TFs might be ACE2 regulators with signal transducer and activator of transcription 3 (Stat3) as the most significant one. In human normal lung tissues, the expression of ACE2 was positively correlated with phosphorylated Stat3 (p-Stat3). We demonstrated that Stat3 bound ACE2 promoter, and controlled its expression in 16HBE cells stimulated with interleukin 6 (IL-6). To screen for medicinal compounds that could modulate ACE2 expression, we conducted luciferase assay using HLF cells transfected with ACE2 promoter-luciferase constructs. Among the 64 compounds tested, 6-O-angeloylplenolin (6-OAP), a sesquiterpene lactone in Chinese medicinal herb Centipeda minima (CM), represented the most potent ACE2 repressor. 6-OAP (2.5 µM) inhibited the interaction between Stat3 protein and ACE2 promoter, thus suppressed ACE2 transcription. 6-OAP (1.25-5 µM) and its parental medicinal herb CM (0.125%-0.5%) dose-dependently downregulated ACE2 in 16HBE and Beas-2B cells; similar results were observed in the lung tissues of mice following administration of 6-OAP or CM for one month. In addition, 6-OAP/CM dose-dependently reduced IL-6 production and downregulated chemokines including CXCL13 and CX3CL1 in 16HBE cells. Moreover, we found that 6-OAP/CM inhibited the entry of SARS-CoV-2 S protein pseudovirus into target cells. These results suggest that 6-OAP/CM are ACE2 inhibitors that may potentially protect lung epithelial cells from SARS-CoV-2 infection.

[Waxing and waning pulmonary nodules and cavities].

We reported a case of vascular Ehlers-Danlos syndrome presenting with recurrent pulmonary hemorrhage. A 22-year-old man was admitted for intermittent hemoptysis and chest pain during the past 18 months. Computed tomography of chest showed bilateral nodules and cavities with halo sign. Inflammatory markers, including erythrocyte sedimentation rate, C reactive protein and interleukin 6, were within normal range. The microbiological and pathological examination of bronchoalveolar lavage fluid and CT-guided percutaneous lung biopsy failed to draw a diagnosis. The pulmonary lesions waxed and waned despite empirical antibacterial, antifungal, antimycobacterial, and anti-parasite treatment. Video-assisted thoracoscopic lung biopsy showed pulmonary hemorrhage, hematoma, ossification, and fibrous nodules, suggesting vascular Ehlers-Danlos syndrome. The molecular testing revealed a heterozygous missense variant in the COL3A1 gene which confirmed the diagnosis of vascular Ehlers-Danlos syndrome. The patient had no skin hyperextensibility or joint hypermobility. During 3-year follow-up, there were no evidence of other vascular or organ involvement except he had intermittent minor hemoptysis. Through this clinical pathological discussion, we aimed to remind pulmonologist to consider the possible diagnosis of vascular Ehlers-Danlos syndrome in young patients with recurrent hemoptysis and waxing and waning pulmonary nodules, cavities, or cysts on CT scan who has neither obvious systematic inflammation nor effective reaction on empirical antimicrobial therapy. Molecular testing should be carried out as soon as possible in a suspected patient to avoid unnecessary invasive examinations.

[Subcutaneous nodules, mediastinal and hilar lymphadenopathy].

A 52-year old man was admitted to our hospital because of dyspnea on exertion for 2 months and subcutaneous nodules for 1 month. Chest enhanced CT showed bilateral hilar and mediastinal lymphadenopathy. Bronchial alveolar lavage fluid revealed a CD4+/CD8+ T cell subsets ratio of 4.3 and culture for acid-fast bacillus (AFB) was negative. The pathology of skin nodules and transbronchial needle aspiration biopsy guided by endoscopic ultrasound (EBUS-TBNA) revealed non-caseating necrotizing epithelioid granulomas with negative acid-fast bacilli staining and periodic acid-Schiff staining, which was compatible with sarcoidosis. The patient was diagnosed as sarcoidosis and glucocorticoid was administrated. The subcutaneous nodules were improved. However, the lymph nodes were enlarged instead of shrinking after 6-month therapy. The failure to respond to glucocorticoids raised the possibility of sarcoidosis complicated with tuberculosis infection. The patient received anti-tuberculosis therapy. Lymphadenopathy responded within 4 months, and there was complete regression after 18-month treatment. The patient was followed up for 5 years and repeated chest CT scan showed that the sizes of bilateral hilar and mediastinal lymph nodes were normal.

[Diagnostic value of surgical lung biopsies for diffuse parenchymal lung disease: the change of disease spectrum in the past 28 years in a single institution in China].

Objective: To investigate the changes of disease spectrum in diffuse parenchymal lung disease (DPLD) diagnosed by surgical lung biopsy, and to explore the diagnostic value of surgical lung biopsy in DPLD. Methods: Four hundred and fifty-five consecutive DPLD patients, who underwent surgical lung biopsy in Peking Union Medical College Hospital during the past 28 years, were analyzed retrospectively. Results: There were 211 males and 244 females. The average age at biopsy was (45±14) years. Four hundred and eleven cases (90.3%) were diagnosed by pathologic findings. Four hundred and forty-one cases (96.9%) were diagnosed by clinical-radiologic-pathologic multidisciplinary discussion. The 30-day mortality and 90-day mortality were 2.4% and 3.3% respectively. The disease spectrum included interstitial pneumonia in 209 cases (45.9%) (nonspecific interstitial pneumonia in 105 cases, usual interstitial pneumonia in 33 cases), other miscellaneous DPLD in 166 cases (36.5%) (including hypersensitivity pneumonitis in 49 cases), tumor in 39 cases (8.6%), and infectious diseases in 27 cases (5.9%). In the three consecutive periods (1993-2002, 2003-2012 and 2013-2020), the number of biopsies was 76 (16.7%), 297 (65.3%) and 82 (18%) respectively. The disease spectrum changes over time: in the above three periods, the percentage of interstitial pneumonia in DPLD was 68.4%, 45.1% and 28%, other miscellaneous DPLDs were 22.4%, 39.4% and 39.0%, the tumors were 2.6%, 7.4% and 18.3%, the infectious diseases were 5.3%, 5.1% and 9.8%. Conclusions: This study presented the changes of disease spectrum in DPLD diagnosed by surgical lung biopsy through single center real-world data, reflecting the progress of clinicians' understanding of DPLD and interstitial pneumonia. Surgical lung biopsy is still valuable for some difficult and complicated DPLD cases.

[Cough, bloody sputum, eosinophil elevation and lung shadow].

A 47-year-old man was referred to the pulmonary clinic with a 2-year history of productive cough and 3-month history of hemoptysis. Two years ago, his chest CT scan revealed a 2 cm×2 cm well-defined nodule in the right upper lung. His cough was alleviated without treatment. Three months ago, he had a productive cough with the bloody sputum after a running to catch the bus. Physical examination was normal. Complete blood count (CBC) showed an elevated eosinophil count (42.61%). Chest CT scan showed that the enlargement of the right upper lobe nodule (3.4 cm×3.3 cm), with bilateral pathy lesions distributed in the right upper lobe and the left lower lobe. Pathological study of needle specimen biopsy showed the lamellated cyst wall of hydatid cyst, brood capsule formation and hooklet. Pulmonary hydatidosis was diagnosed. It was recommended that the patient should be treated by surgery combined with albendazole. His symptoms relieved and lung nodules were shrinking without treatment after 5 years follow-up.

The association of different serum IgG4 levels with distinct clinical characteristics and treatment efficacy in patients with IgG4-related disease.

OBJECTIVSE: To explore the clinical characteristics and treatment efficacy of IgG4-related disease (IgG4-RD) patients with different levels of serum IgG4. METHODS: A total of 299 patients newly diagnosed with IgG4-RD were enrolled in this study. Patients were classified into four groups according to baseline serum IgG4 levels: Group A: normal concentration; Group B: > normal but <2× the upper reference limit (URL); Group C: between 2× and 5× the URL; Group D: >5× the URL. All patients were followed up for 12 months. The patients' clinical characteristics, laboratory parameters, plasmablasts/plasma cells and treatment efficacy were analysed. RESULTS: IgG4-RD patients with higher serum IgG4 levels had higher percentages of dacryoadenitis, sialadenitis, and autoimmune pancreatitis and a higher prevalence of allergy history, whereas patients with retroperitoneum and mediastinum lesions usually had lower serum IgG4 levels. In addition, the serum IgG4 re-elevation rate in Group D (19.4%) was higher than those in Group B (4.9%) and Group C (7.7%) (p=0.003 and p=0.020, respectively). Patients suffered fewer clinical relapses with a serum IgG4 reduction ≥50% of baseline serum IgG4 in Group B and ≥40% of baseline serum IgG4 in Group D (p=0.019 and p=0.043, respectively). In addition, the rate of clinical relapse in patients who received combination therapy with glucocorticoids and mycophenolate mofetil was 18.75% in Group D, which was higher than the rates in Groups B and C (0) (p=0.027). CONCLUSIONS: IgG4-RD patients with different levels of serum IgG4 exhibit different clinical characteristics and treatment responses.

The value of transbronchial lung biopsy in the diagnosis of lymphangioleiomyomatosis.

BACKGROUND: Transbronchial lung biopsy (TBLB) in the diagnosis of lymphangioleiomyomatosis (LAM) is not a common approach, although TBLB is often performed in diffuse lung diseases. We aimed to examine the diagnostic value and safety of TBLB in LAM patients based on the data collected in our center. METHODS: We reviewed LAM patients registered in our LAM Clinic from December 8, 2006, to December 31, 2019. All patients with definite or probable diagnosis of LAM who had been examined using TBLB were included. All available pathology slides were reviewed by an experienced LAM pathologist. All complications were reviewed by the medical records and confirmed using telephone interviews. RESULTS: The pathology results of 86 patients (including 74 definite LAM and 12 probable LAM) were available. The positive rate of TBLB in LAM patients was 49/86 (57.0%). The positive rates of SMA, HMB-45, ER, and PR in LAM patients were 97.6%, 93%, 84.6%, and 78.4% respectively. The positive rate of TBLB was 40%, 60% and 60.8% in patients with CT Grade I, Grade II, and Grade III respectively, and the difference was not significant. Patients who had 3-4 or 5-6 biopsied specimens had a higher rate of diagnosis than those with 1-2 biopsied specimens. Four patients (5.6%) reported pneumothorax. No major hemoptysis was reported. CONCLUSIONS: TBLB is a feasible and safe procedure for obtaining a pathological diagnosis of LAM. Taking more than 2 samples during the biopsy procedure increased the rate of diagnosis.

Lymphangioleiomyomatosis.

Lymphangioleiomyomatosis (LAM) is a slow albeit progressive rare neoplastic disease featured with diffuse thin-walled cysts in lungs and angiomyolipomas in kidneys. LAM affects almost exclusively women and has one of the strongest gender predispositions of any extragenital human disease. Two forms of LAM present clinically, sporadic (S-LAM) and tuberous sclerosis complex-associated (TSC-LAM). TSC is an autosomal dominant genetic multisystems neoplastic disease. A high prevalence of LAM can be detected in adult female TSC patients. Tremendous progress has been made in our understanding and management of this rare disease. Both LAM and TSC are TSC2 or TSC1 mutated diseases that result in overactivation of the mechanistic target of rapamycin (mTOR) pathway. Sirolimus, an mTOR inhibitor, has been approved for LAM treatment in the United States and many other countries. Therapies targeting female sex hormones have shown preclinical efficacy in animal and cell culture-based experiments, but have not been properly investigated clinically. In this review, we summarize current recommendations in the diagnosis and treatment of LAM.

IgG4-related disease can present as recurrent spontaneous hemothorax: a case report.

BACKGROUND: Immunoglobulin G4-related disease (IgG4-RD) encompasses a group of immune-mediated disorders that are gaining increasing recognition. Pulmonary presentations are common, with four types of patterns been described on radiography, including solid nodular, bronchovascular, ground glass opacities, and alveolar interstitial. Pleural thickening and pleural effusion have also been reported. However, there have been no reports of IgG4-RD that presents as spontaneous hemothorax. CASE PRESENTATION: A 61-year-old Chinese woman experienced recurrent right-sided chest pain and transient syncope. A significant decrease in her hemoglobin level and thick bloody pleural fluid demonstrated spontaneous hemothorax. The elevated serum IgG4 and histopathological analysis of the right pleura and intercostal lymph node specimens all supported the diagnosis of IgG4-RD in this patient. Further diagnostic evaluation did not reveal other causes for spontaneous hemothorax. She received steroids and no recurrent bleeding event occurred during a follow-up period of more than 1 year. CONCLUSION: Recurrent spontaneous hemothorax can be a rare manifestation of IgG4-RD, with pleural involvement as the most probable mechanism.

[Clinical Features of Coccidioidomycosis:Analysis of 33 Chinese Cases].

Objective To summarize the characteristics of Chinese coccidioidomycosis cases, improve the diagnosis and treatment of this disease and prevent misdiagnosis as well as therapeutic error.Methods Search in databases including Medline,Wanfang,and CNKI using "Coccidioidomycosis" and "China" as index words yielded 23 articles that reported a total of 32 Chinese coccidioidomycosis cases.In addition,one patient with disseminated coccidioidomycos was treated in our center in April 2016.The demographic data,site of infection,clinical manifestations,past medical history,exposure history,imaging and laboratory findings,and pathological features of these 33 patients were analyzed.Results Among these 33 patients,7(21.2%)had visited an epidemic area and 6(18.2%)were immunocompromised.The disease involved the respiratory system,skin,bone,central nervous system,cornea,and stomach in 24,6,3,2,1,and 1 patients,respectively.Eight patients (24.2%) had multiple system involvement,and three of them died.The imaging findings included pulmonary nodules(n=14),mediastinal lymphadenopathy(n=5),solid shadow(n=4),cavity(n=4),pleural effusion(n=3),multiple plaques(n=2)and masses(n=2).Coccidiolys cysts were detected in the affected tissues(n=28)or in pus,exudate or pleural smear(n=3);in addition,coccidioides mycelium and spores were found in the sputum,pus,and tissue cultures in 4 cases,among whom only 2 cases were confirmed by serological examination.The treatments included triazoles(n=20),systemic or local administration of amphotericin B(n=13),surgical resection of the lesion(n=8),and intravenous gamma globulin(n=1).Five patients died,among whom three had underlying diseases that caused immunosuppression and one was an infant.The prognoses were relatively good in the remaining patients.Conclusions Early diagnosis and proper treatment can achieve good prognosis in coccidioidomycosis patients.Multi-system involvement and immunosuppression are risk factors for poor prognosis of coccidioidomycosis.For these patients,adequate and full-course medication may prevent rapid disease progression.

Secondary pulmonary alveolar proteinosis: a single-center retrospective study (a case series and literature review).

BACKGROUND: Secondary pulmonary alveolar proteinosis (sPAP) is an extremely rare disease. The clinical features of sPAP patients remain to be summarizeds. METHODS: Patients pathologically diagnosed with PAP and with negative results for anti-granulocyte macrophage colony stimulating factor (GM-CSF) autoantibodies from Peking Union Medical College Hospital between January 2000 and July 2016 were retrospectively studied. The PubMed database was also searched for literature to collect published cases. RESULTS: In our center, nine patients were diagnosed as sPAP with a median age of 37 years. Hematological disorders, including myelodysplastic syndrome (MDS), chronic myelogenous leukemia (CML), and pulmonary tuberculosis (TB) infection were the underlying diseases. Cases secondary to MDS had very poor prognosis as all of them survived less than 2 years after their diagnosis, while those secondary to TB had favorable prognosis. Only 33.3% of cases showed interlobular septal thickening in our sPAP group. Through literature review, 164 sPAP cases were collected. The age at diagnosis was 45.0 ± 14.8 years old and the gender radio was 1.20:1 (M:F). 61.9% of cases were diagnosed by bronchoscopy. MDS and CML were common underlying diseases in 34.1% and 15.2% of patients, respectively. Patients with sPAP secondary to hematological diseases had a short survival time and half of them died within 14.95 months after diagnosis. CONCLUSIONS: MDS and TB infection were the most frequent underlying causes of sPAP in this single-center research in China, with cases secondary to MDS having a poor survival rate. sPAP was more likely to be secondary to hematological disorders, especially MDS and CML and had a fairly poor prognosis in published cases. sPAP should be suspected in PAP patients whose CT scan presents only ground-glass opacities without interlobular septal thickening.

Organizing pneumonia components in non-specific interstitial pneumonia (NSIP): a clinicopathological study of 33 NSIP cases.

AIMS: To review the clinical, radiological and pathological features of non-specific interstitial pneumonia (NSIP), mainly to characterize organizing pneumonia (OP) components in NSIP. METHODS AND RESULTS: Lung biopsy samples from 33 NSIP patients were collected over a period of 10 years. Microscopic analysis revealed that 13 cases showed a cellular pattern and 20 showed a mixed/fibrosing pattern. OP components were detected in 26 cases (13 with a cellular pattern; 13 with a mixed/fibrosing pattern), and were found to constitute a median proportion of 9% (range, 1-40%) of the affected tissues. In nine cellular and four mixed/fibrosing NSIP cases, the OP components accounted for ≥10%. A proportion of ≥20% was found in only five cellular pattern cases. Twenty-nine patients were followed up: 17 showed improvements, five were stabilized, and seven showed progression. CONCLUSIONS: OP components are common basic lesions in NSIP cases, although their proportion in cellular and mixed/fibrosing pattern cases varies substantially between patients. OP components do not impact on prognosis, even when they constitute ≥20% of the affected tissue. Thus, a high level of OP components does not exclude a diagnosis of NSIP in cases that otherwise show pathological and radiological findings characteristic of NSIP.

Diffuse Cystic Lung Diseases: Diagnostic Considerations.

Diffuse cystic lung disease (DCLD) is a group of heterogeneous diseases that present as diffuse cystic changes in the lung on computed tomography of the chest. Most DCLD diseases are rare, although they might resemble common diseases such as emphysema and bronchiectasis. Main causes of DCLD include lymphangioleiomyomatosis, Birt-Hogg-Dubé syndrome, pulmonary Langerhans cell histiocytosis, lymphoid interstitial pneumonia, amyloidosis, light-chain deposition disease, Sjögren syndrome, and primary or metastatic neoplasm. We discuss clinical factors that are helpful in the differential diagnosis of DCLDsuch as sex and age, symptoms and signs, extrapulmonary presentations, cigarette smoking, and family history. Investigations for DCLD include high-resolution computed tomography, biochemical and histopathological studies, genetic tests, pulmonary function tests, and bronchoscopic and video-assisted thoracoscopic biopsies. A proposed diagnostic algorithm would enhance ease of diagnosing most cases of DCLD.

Coexistence of pulmonary lymphangioleiomyomatosis and pulmonary angiomyolipoma.

BACKGROUND: Lymphangioleiomyomatosis (LAM) and angiomyolipoma are two different, but related rare diseases. To the best of our knowledge, pulmonary LAM and pulmonary angiomyolipoma have not previously been observed in the same patient. CASE PRESENTATION: A 38-year-old woman presented with a dry cough and left flank pain. She had a right nephrectomy for renal angiomyolipoma 17 years ago. A magnetic resonance imaging scan demonstrated a round mass in the left kidney. A chest computed tomography scan demonstrated scattered small thin-walled cysts and multifocal round nodules in both lungs. A lung biopsy via video-assisted thoracoscopic surgery revealed that the cysts and nodules were manifestations of LAM and angiomyolipomas, respectively. After sirolimus therapy, the renal angiomyolipoma and metastasized pulmonary angiomyolipomas shrank, but pulmonary cysts were unchanged. CONCLUSIONS: LAM and angiomyolipoma are significantly associated, and may coexist in the lungs in rare cases. Sirolimus is effective for both renal angiomyolipoma and metastasized pulmonary angiomyolipomas.

Biopsy-proven IgG4-related lung disease.

BACKGROUND: Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory disorder that may involve single or multiple organs. Biopsy-proven lung involvement of this disease is occasionally reported, but not well understood. METHODS: Patients with the diagnosis of biopsy-proven IgG4-related lung disease (IgG4-RLD) from Peking Union Medical College Hospital between January 2011 and July 2015 were retrospectively analyzed. Age, sex, clinical symptoms, laboratory findings, pulmonary function test results, chest CT tests, positron emission tomography (PET) examinations, treatments and prognoses were retrieved from medical records and analyzed. RESULTS: Seventeen patients were included in this study (mean age: 44.8 ± 15.0 years). Ten patients were diagnosed via surgery, and 7 patients were diagnosed via percutaneous transthoracic core-needle lung biopsy. Extrapulmonary involvement was observed in only one patient. The clinical symptoms included cough, fever, dyspnea, chest pain and hemoptysis. The serum IgG4 concentration was elevated in 7/13 patients (mean: 1955 ± 1968 mg/L). The chest CT findings included mainly nodules and masses with spiculated borders, alveolar consolidations with air bronchograms, and ground glass opacities with or without reticular opacities. PET scans indicated increased standardized uptake values, and 7/8 patients were correctly diagnosed with benign inflammation. Corticosteroids and immunosuppressants were administered to 14/17 patients and effectively alleviated the disease. CONCLUSIONS: In biopsy-proven IgG4-RLD, a normal serum IgG4 concentration is commonly seen, while extrapulmonary involvement is infrequent. Alveolar consolidation with air bronchograms is an important imaging finding of IgG4-RLD, which has not been emphasized before.

Computed Tomographic and Pathological Features of Primary Pulmonary Sarcomatoid Carcinoma.

OBJECTIVE: To investigate the computed tomographic (CT) and pathological features of primary pulmonary sarcomatoid carcinoma (PSC). METHODS: The clinical data and CT images of 20 patients with pathologically confirmed PSC were retrospectively analyzed. RESULTS: Solitary pulmonary mass was identified in 18 patients and multiple pulmonary masses in 2 patients, amounting to 22 masses. There were 17 peripheral masses and 5 central masses, including 11 masses larger than 5 cm. The smooth margin was identified in 9 masses, deep lobulation and/or spinous protuberance in 11 masses, and ill-defined margin in 2 masses. Pleural indentation was identified in 2 masses and pleural thickening with wide basement was identified in 14 masses. On plain CT, cavity was observed in 5 masses, hypo-density in 7 masses, and homogeneous density in 10 masses. On contrast-enhanced CT scanning, irregular ring/patchy enhancement were shown in 15 masses and slightly homogenous enhancement in 2 masses. Of all patients, 6 patients had unilateral or bilateral hilar and/or mediastinal lymphadenopathy. There were 16 pleomorphic carcinomas and 4 spindle cell carcinomas. Immunohistochemically, anti-pan cytokeratin antibody was positive in 13 patients, cytokeratin was positive in 8 patients, Vimentin was positive in 15 patients, epithelial membrane antigen was positive in 1 patient, and thyroid transcription factor-1 was positive in 8 patients. CONCLUSION: PSC has some specific CT features; however, the final confirmation of PSC still depends on pathological and immunohistochemical examinations.

IgG4-related kidney disease from the renal pelvis that mimicked urothelial carcinoma: a case report.

BACKGROUND: IgG4-related kidney disease is a comprehensive term for renal lesions associated with IgG4-related disease, which mainly manifests as plasma cell-rich tubulointerstitial nephritis with increased IgG4+ plasma cells and fibrosis. IgG4-related kidney disease in the renal pelvis is rare. CASE PRESENTATION: We describe a 53-year-old Asian woman who was referred to our hospital with a space-occupying renal lesion discovered by medical examination. A physical examination and laboratory evaluation revealed no significant abnormalities. Computed tomography scans showed a soft-tissue mass with an irregular border and mild homogeneous enhancement in the right renal pelvis and calyces. A positron emission tomography/computed tomography scan revealed soft-tissue density shadows with increased radionuclide uptake. To investigate a suspected pelvic carcinoma, a right ureteronephrectomy was performed. A pathologic examination of the renal sections showed a dense lymphoplasmacytic infiltrate rich in IgG4+ plasma cells, with fibrosis beneath the urothelial epithelium of the renal pelvis. Postoperatively, the serum IgG4 level was significantly elevated. The patient was diagnosed with IgG4-related kidney disease. CONCLUSION: We present a case of IgG4-related kidney disease mimicking urothelial carcinoma in the renal pelvis. When a buried and solitary hypovascular tumor is detected in the kidney, we must consider IgG4-related kidney disease as a differential diagnosis. Accordingly, elevated serum IgG4, radiologic findings, and pathologic examination may improve the diagnosis.