IgG4‐related disease

Immunoglobulin G4‐related disease (IgG4‐RD) is a regional or systemic fibro‐inflammatory disease of unknown etiology. It presents a distinctive histopathological appearance of dense lymphoplasmacytic infiltrates with abundant IgG4‐positive plasma cells, storiform fibrosis and obliterative phlebitis with the appearance of inflammatory swelling or tumefactive lesions. This new disease entity includes a wide variety of diseases such as Mikulicz disease, autoimmune pancreatitis, Riedel thyroiditis, interstitial nephritis and retroperitoneal fibrosis. Glucocorticoid therapy can resolve the clinical and pathological abnormalities and impaired organ function. IgG4‐RD was recognized internationally in 2011, and new evidence has accumulated regarding its pathogenesis, clinical features and treatment. In this review, we outline our present understanding of IgG4‐RD.     

IgG4‐related retroperitoneal fibrosis: a newly characterized disease

Retroperitoneal fibrosis (RPF) is a rare disease characterized by chronic, nonspecific inflammatory and sclerotic or fibrotic tissue in the periaortic or periiliac retroperitoneum that encases adjacent structures. There will be a series of clinical manifestations once the proliferated fibrous tissues encase the abdominal aorta, iliac arteries and urinary duct. RPF is generally divided into two types: idiopathic retroperitoneal fibrosis (IRPF) without identified pathogenesis, making up about two‐thirds of cases, and secondary retroperitoneal fibrosis. Recent studies on Immunoglobulin G4‐related disease (IgG4‐RD) reveal that abundant infiltration of IgG4 positive plasma cells is found in biopsies on the mass of RPF of some IRPF patients, which is identified as one spectrum of IgG4‐RD and is named IgG4‐related RPF. IgG4‐related RPF is often misdiagnosed as retroperitoneal visceral malignancy and is treated with surgery. In addition, because of its good response to glucocorticoid, early detection and treatment is important. We review the definition, epidemiology, clinical features, diagnostic criteria, treatment and prognosis of IgG4‐related RPF in this article to raise awareness of this newly characterized disease.     

IgG4‐related disease and lymphocyte‐variant hypereosinophilic syndrome: A comparative case series

Chronic lymphocytic leukaemia (CLL) is a chronic B‐cell lympho‐proliferative disorder in which lymphomatous transformations occur in 5%‐15% of patients. Histologically these cases resemble diffuse large B‐cell lymphoma, or Richter's transformation, in over 80% of cases. Rare cases of transformation to Hodgkin lymphoma (HL) have been reported in the literature with an estimated prevalence of 0.4%. We report a case of a 67‐year‐old female with CLL treated with the novel Bruton's tyrosine kinase (Btk) inhibitor, ibrutinib, who subsequently presented with intractable fevers. Bone marrow trephine, and lymph node biopsy revealed classical HL with negative immuno‐histochemistry for Btk in HL cells, on a backdrop of CLL. The patient commenced treatment with Adriamycin, Vinblastine and Dacarbazine (AVD), which resulted in an excellent response. Hodgkin transformation of CLL is rare with a single retrospective study of 4121 CLL patients reporting only 18 cases. Btk expression in HL cells is recently recognised in classical HL; however, the majority of HLs are Btk negative. Given that Btk inhibitors have recently been shown to induce genomic instability in B cells, in the context of their widespread use, such emerging cases are increasingly relevant.     

Marked accumulation of fluorodeoxyglucose and inflammatory cells expressing glucose transporter‐3 in immunoglobulin G4‐related autoimmune hepatitis

Immunoglobulin (Ig)G4‐related autoimmune hepatitis (AIH) is a recently proposed subtype that responds well to steroid treatment; however, its pathogenesis remains unclear. We report here a 65‐year‐old Japanese woman with skin itching and lip swelling. She had liver injury with jaundice, which persisted despite stopping anti‐allergic agents. Blood chemistry revealed highly elevated serum IgG and IgG4 (535 mg/dL) levels, and positive anti‐nuclear antibody. The diagnosis of AIH was based on liver biopsy. Notably, the IgG4⁺/IgG⁺ cell ratio was 85%. On fluorodeoxyglucose (FDG) positron emission tomography/computed tomography, robust signal intensity was found in the liver, and in enlarged lymph nodes and salivary glands with confirmed IgG4⁺ cell infiltration. Immunofluorescence analysis of the liver biopsy specimen indicated clear expression of glucose transporter‐3 (Glut‐3) in IgG4⁺ inflammatory cells infiltrating into the portal area. This is the first report of simultaneous strong accumulation of FDG and Glut‐3 expression in IgG4‐related AIH, which might aid in elucidating the pathogenesis of this disease.     

Medical mirroring: granulomatosis with polyangiitis (formerly Wegener's) mimicking immunoglobulin‐G4 related disease

Granulomatosis with polyangiitis (GPA; formerly Wegener's) can present with clinical and histopathological features similar to those of immunoglobulin‐G4 related disease (IgG4‐RD), a recently described fibro‐inflammatory condition. The ability of these two distinct entities to mimic each other closely creates significant pitfalls in diagnosis. We present a unique case in which GPA presented as a peri‐aortic fibrotic mass in the retroperitoneum. The patient's other clinical features also overlapped with classic IgG4‐RD disease manifestations, but the histopathology in two organs and the serological data confirmed the diagnosis of GPA. Rigorous histopathological review remains the gold standard for the diagnosis of GPA and the distinction of this entity from IgG4‐RD and other mimickers.     

IgG4‐related disease with hypergammaglobulinemic hyperviscosity and retinopathy

Immunoglobulin G4‐related disease (IgG4‐RD) is a recently described entity with protean manifestations. We describe a novel case of IgG4‐RD with hypergammaglobulinemic hyperviscosity responsive to fludarabine and rituximab. A 33‐year‐old Asian man developed bilateral lacrimal gland and submandibular salivary gland swelling with cervical lymphadenopathy. Biopsies of the affected tissues revealed reactive follicular hyperplasia. Seven years later, he presented with bilateral retinal hemorrhages due to hyperviscosity syndrome from profound polyclonal increase in IgG, including marked IgG4 elevation. Despite plasmapheresis, overproduction of IgG continued and he was refractory to systemic steroids, azathioprine, interferon alpha, and cyclophosphamide. IgG4‐RD was suspected following a myocardial infarction and detection of aneurysmal coronary arteries indicating large vessel vasculitis. Review of the cervical lymph node and lacrimal gland biopsies with immunohistochemical staining for IgG4‐positive plasma cells confirmed IgG4‐RD. B‐cell depletion with rituximab produced a partial response, but clinical symptoms and elevated protein levels persisted. Fludarabine was added to rituximab to suppress T‐cell activity, and this resulted in an excellent clinical and biochemical response. Combination therapy with fludarabine and rituximab in IgG4‐RD has not previously been reported and can be considered in patients with severe refractory disease.     

IgG4-related retroperitoneal fibrosis: the first reported case in a Chinese population

Immunoglobulin G4 (IgG4)-related sclerosing disease is a newly recognized clinicopathological entity characterized by lymphoplasmacytic infiltration and varying degrees of fibrosis in various organs, with abundant IgG4-positive plasma cells in tissues. Patients usually exhibit multisystem involvement and often respond well to steroid and immunosuppressive therapy. However, this disease has been rarely reported in a Chinese population. We herein report a case of IgG4-related sclerosing disease solely presenting with retroperitoneal fibrosis that was effectively treated with systemic steroid therapy. To the best of our knowledge, this is the first reported case of IgG4-related retroperitoneal fibrosis in a Chinese population.