Recognizing IgG4-related tubulointerstitial nephritis

Phospholipase A2 receptor-negative membranous nephropathy presenting as a rare renal manifestation of IgG4-related disease

IgG4-related disease is a fibroinflammatory condition characterized by dense lymphoplasmacytic infiltrates rich in IgG4-positive plasma cells affecting multiple organs. Though the most common renal manifestation of IgG4-related disease is tubulointerstitial nephritis, it can rarely present as secondary membranous nephropathy. We present a case of a 75-year-old male with phospholipase A2 receptor-negative membranous nephropathy as an atypical manifestation of IgG4-related disease. The patient presented with nephrotic syndrome and was found to have elevated serum IgG4 levels and IgG4-positive plasma cells in the kidney biopsy. He was successfully treated with corticosteroids and rituximab, resulting in significant improvement in proteinuria and normalization of IgG4 levels. This case highlights the importance of considering IgG4-related disease in patients with phospholipase A2 receptor-negative membranous nephropathy, especially in those with a history of other organ involvement. Early recognition and treatment of IgG4-related disease are crucial to prevent progressive kidney damage and improve patient outcomes.

Renal Manifestations of IgG4-Related Disease: A Concise Review

IgG4-related disease (IgG4-RD) is an immune-mediated disorder marked by fibro-inflammatory masses that can infiltrate multiple organ systems. Due to its relatively recent discovery and limited understanding of its pathophysiology, IgG4-related disease may be difficult to recognize and is consequently potentially underdiagnosed. Renal involvement is becoming regarded as one of the key features of this disease. To date, the most well-recognized renal complication of IgG4-related disease is tubulointerstitial nephritis, but membranous glomerulonephritis, renal masses, and retroperitoneal fibrosis have also been reported. This concise review has two objectives. First, it will briefly encapsulate the history, epidemiology, and presentation of IgG4-related disease. Second, it will examine the reported renal manifestations of IgG4-related disease, exploring the relevant histology, imaging, clinical features, and treatment considerations. This synthesis will be highly relevant for nephrologists, rheumatologists, general internists, and renal pathologists to raise awareness and help improve early recognition of IgG4-related kidney disease (IgG4-RKD).

IgG4-related disease. Clinical manifestation differential diagnosis and recent International Diagnostic Criteria for IgG4-related disease

Immunoglobulin G4- related disease (IgG4-RD) is a rare systemic fibro-inflammatory disorder. Autoimmune pancreatitis is the most frequent manifestation of IgG4-RD. However, IgG4-RD can affect any organ such as salivary glands, orbits, retroperitoneum, prostate and many others. Recent research enabled a clear clinical and histopathological description of IgG4-RD and in 2019 four Clinical phenotypes of IgG4-related disease were described. Diagnosis is based on morphological examination with typical findings of lymphoplasmocellular inflammation, storiform fibrosis and obliterative phlebitis in IgG4-RD biopsies and the tissue invading plasma cells largely produce IgG4. Elevated serum IgG4 levels are found in many but not all patients. New diagnostic criteria for IgG4-RD have been published recently in 2019 and 2021. This review summarizes current knowledge on pathophysiology, clinical manifestations, diagnosis and differential diagnosis of IgG4-RD from the point of view 2022 and in next article brings overview of the IgG4-RD therapy.

Folic acid-induced animal model of kidney disease

The kidneys are a vital organ that is vulnerable to both acute kidney injury (AKI) and chronic kidney disease (CKD) which can be caused by numerous risk factors such as ischemia, sepsis, drug toxicity and drug overdose, exposure to heavy metals, and diabetes. In spite of the advances in our understanding of the pathogenesis of AKI and CKD as well AKI transition to CKD, there is still no available therapeutics that can be used to combat kidney disease effectively, highlighting an urgent need to further study the pathological mechanisms underlying AKI, CKD, and AKI progression to CKD. In this regard, animal models of kidney disease are indispensable. This article reviews a widely used animal model of kidney disease, which is induced by folic acid (FA). While a low dose of FA is nutritionally beneficial, a high dose of FA is very toxic to the kidneys. Following a brief description of the procedure for disease induction by FA, major mechanisms of FA-induced kidney injury are then reviewed, including oxidative stress, mitochondrial abnormalities such as impaired bioenergetics and mitophagy, ferroptosis, pyroptosis, and increased expression of fibroblast growth factor 23 (FGF23). Finally, application of this FA-induced kidney disease model as a platform for testing the efficacy of a variety of therapeutic approaches is also discussed. Given that this animal model is simple to create and is reproducible, it should remain useful for both studying the pathological mechanisms of kidney disease and identifying therapeutic targets to fight kidney disease.

Case Report: Predominant Tubulointerstitial Lupus Nephritis or the Combination With IgG4-Related Disease?

Isolated or dominant tubulointerstitial lupus nephritis is rare. Here, we reported a 67-year-old man diagnosed with systemic lupus erythematosus (SLE) based on clinical and laboratory criteria, who was showing impaired renal function and non-nephrotic range proteinuria in the past 2 years. Renal biopsy showed almost normal glomeruli, but the tubulointerstitium showed “storiform” pattern with interstitial infiltration of IgG3 predominant plasma cells. Immunofluorescence showed linear and granular staining of IgG and C1q along TBM and interstitium. He started on medium dose of oral steroids and mycophenolate mofetil, which were gradually tapered. As a result, his renal function improved over a few days. Now, he continued on low dose steroids and mycophenolate mofetil with no evidence of relapse.

Imaging findings of IgG4-related kidney disease without extrarenal organ involvement: A case report

RATIONALE

IgG4-related disease (IgG4-RD) is a systemic chronic inflammatory disorder that can affect almost every organ. IgG4-RD includes IgG4-related kidney disease (IgG4-RKD), but lesions affecting the kidney alone or first are very rare, and a complete understanding is lacking. Computed tomography (CT) and magnetic resonance imaging (MRI) findings can show the typical characteristics of IgG4-RKD and provide information for accurate and rapid diagnosis.

PATIENT CONCERNS

We report a case of a 60-year-old woman who was admitted to our hospital for dizziness and instability while walking, her bilateral eyelids were also slightly swollen. She had no medical history.

DIAGNOSES

CT and MRI images of the patient revealed multiple local and diffuse patchy lesions in the bilateral renal parenchyma and mass-like tissue in the bilateral renal pelvis, accompanied by right hydronephrosis. A pathological examination of renal samples showed numerous lymphocyte and plasma cell infiltration. Immunohistochemistry demonstrated approximately 50% of the IgG-positive plasma cells to be IgG4+. The serum IgG level was obviously elevated, with both C3and C4 levels were reduced. The patient was diagnosed with IgG4-RKD.

INTERVENTIONS

The patient received corticosteroid therapy at another hospital.

OUTCOMES

The bilateral kidney lesions were smaller on follow-up CT images.

LESSONS

IgG4-RKD exhibits some characteristic imaging features. Despite the relatively low incidence of IgG4-RKD, it should be included in differential diagnoses when images show multiple lesions in kidneys with mild and delayed enhancement and hypointensity on T2WI in middle-aged to elderly patients.

Imaging features of immune-mediated genitourinary disease

PURPOSE

Imaging features of immune-mediated genitourinary diseases often overlap, and the same disease may manifest in different ways, so understanding imaging findings in the context of the patient's entire clinical picture is important in providing the correct diagnosis.

METHODS

In this article, diseases mediated by the immune system which affect the genitourinary system are reviewed. Examples of immune-mediated genitourinary disease including IgG4-related disease, post-transplant lymphoproliferative disorder, immunodeficiency-associated lymphoproliferative disorder due to immunosuppressive and immunomodulatory medications, lymphoma, leukemia, myeloma, amyloidosis, and histiocytosis.

RESULTS

Clinical and imaging features will be presented which may help narrow the differential diagnosis for each disease.

CONCLUSION

Recognition of immune-related genitourinary disease is important for appropriate medical management as they may mimic other diseases both by imaging and clinical presentation.

IgG4-related disease: what a hematologist needs to know

IgG4-related disease is a fibro-inflammatory condition that can affect nearly any organ system. Common presentations include major salivary and lacrimal gland enlargement, orbital disease, autoimmune pancreatitis, retroperitoneal fibrosis and tubulointerstitial nephritis. This review focuses on the hematologic manifestations of IgG4-related disease, including lymphadenopathy, eosinophilia, and polyclonal hypergammaglobulinemia. The disease can easily be missed by unsuspecting hematologists, as patients may present with clinical problems that mimic disorders such as multicentric Castleman disease, lymphoma, plasma cell neoplasms and hypereosinophilic syndromes. When IgG4-related disease is suspected, serum protein electrophoresis and IgG subclasses are helpful as initial tests but a firm histological diagnosis is essential both to confirm the diagnosis and to rule out mimickers. The central histopathological features are a dense, polyclonal, lymphoplasmacytic infiltrate enriched with IgG4-positive plasma cells (with an IgG4/IgG ratio >40%), storiform fibrosis, and obliterative phlebitis. Importantly for hematologists, the latter two features are seen in all tissues except bone marrow and lymph nodes, making these two sites suboptimal for histological confirmation. Many patients follow an indolent course and respond well to treatment, but a significant proportion may have highly morbid or fatal complications such as periaortitis, severe retroperitoneal fibrosis or pachymeningitis. Corticosteroids are effective but cause new or worsening diabetes in about 40% of patients. Initial response rates to rituximab are high but durable remissions are rare. More intensive lymphoma chemotherapy regimens may be required in rare cases of severe, refractory disease, and targeted therapy against plasmablasts, IgE and other disease biomarkers warrant further exploration.

Acute and Chronic Tubulointerstitial Nephritis of Rheumatic Causes

Tubulointerstitial nephritis (TIN) is the second most common cause of acute intrinsic kidney injury after acute tubular necrosis. Although drug-induced forms of TIN represent the vast majority, rheumatic disease is another common cause and often underdiagnosed. Early diagnosis of acute interstitial nephritis and prompt withdrawal of the culprit medication or a correct treatment can avoid chronic damage and progressive chronic kidney disease. This review highlights the recent updates, clinical features, and treatment in TIN in autoimmune rheumatic disease.

A young woman with steroid-responsive, IgG4-positive plasma cell-enriched cystic lymphangioma and chylous ascites

Lymphangiomas are benign tumors of the lymphatic vessels, which can be inflammatory and occasionally steroid-responsive. IgG4-related disease (IgG4-RD) is a recently defined fibro-inflammatory condition. We describe a novel association between reactive IgG4+ plasma cells and cystic lymphangioma in a young woman who had a dramatic clinical response to steroids.