Mimickers of immunoglobulin G4-related hepatobiliary disease on biopsy

With the growing recognition of IgG4-related hepatobiliary disease, establishing a definitive diagnosis relies mainly on a combination of clinical findings, serological markers, and imaging modalities. However, the role of histopathological evaluation remains indispensable, particularly in cases necessitating differential diagnosis or malignancy exclusion. While diagnosing IgG4-related hepatobiliary disease through surgical resection specimens is often straightforward, pathologists encounter substantial challenges when evaluating biopsies. The increasing rarity of surgical interventions exacerbates this due to improved disease recognition and suspicion. Numerous confounding factors, including the absence of the characteristic histologic features, limited tissue sample size, biopsy artifacts, and the limited value of IgG4 counts, further complicate the diagnostic process. Additionally, many other disorders exhibit clinical and histological features that overlap with IgG4-related disease, intensifying the complexity of interpreting biopsy specimens. This article explores the clinical and histomorphologic features of IgG4-related hepatobiliary disease and its potential mimickers. It offers valuable insights for pathologists and clinicians when confronted with biopsy specimens from hepatobiliary organs.

Immunoglobulin G4-related Tubulointerstitial Nephritis with Simultaneous Resolution of Plasma Cell Infiltration and Fibrosis after Steroid Treatment

We performed 3 kidney biopsies in a 71-year-old man. At the first biopsy, we made the diagnosis of immunoglobulin G4 (IgG4)-related interstitial nephritis characterized by the simultaneous presence of IgG4-positive plasma cells and characteristic fibrosis with a bird's-eye pattern. At the second biopsy, rather than finding fibrosis as a post-inflammatory scar, we noted that steroid treatment had caused the simultaneous disappearance of IgG4-positive plasma cells and fibrosis and had restored the normal tubular structure. The third biopsy showed the recurrence of the disease with inflammatory cells accompanied by fibrosis. These findings suggest that IgG4-positive plasma cells and fibrosis occur simultaneously.

Immunoglobulin G4-related Hepatopathy after COVID-19 Vaccination

An 84-year-old woman with immunoglobulin G4 (IgG4)-related disease presented with jaundice and liver dysfunction after COVID-19 vaccination. Serum IgG4 levels were elevated. Diagnostic imaging showed no stenotic lesions in the bile ducts. A liver biopsy was performed because of the enlarged liver. Infiltration of IgG4-positive plasma cells, which accounted for approximately 74% of total plasma cells, was found in the portal area, but there was no evidence of periportal hepatitis, and inflammatory cell infiltration into the lobular space was minimal. IgG4-related hepatopathy was diagnosed. The patient achieved spontaneous remission with no treatment and only follow-up and remains under observation at the time of writing.

Autoimmune Diseases of Digestive Organs-A Multidisciplinary Challenge: A Focus on Hepatopancreatobiliary Manifestation

It is well known that some pathological conditions, especially of autoimmune etiology, are associated with the HLA (human leukocyte antigen) phenotype. Among these diseases, we include celiac disease, inflammatory bowel disease, autoimmune enteropathy, autoimmune hepatitis, primary sclerosing cholangitis and primary biliary cholangitis. Immunoglobulin G4-related diseases (IgG4-related diseases) constitute a second group of autoimmune gastrointestinal, hepatobiliary and pancreatic illnesses. IgG4-related diseases are systemic and rare autoimmune illnesses. They often are connected with chronic inflammation and fibrotic reaction that can occur in any organ of the body. The most typical feature of these diseases is a mononuclear infiltrate with IgG4-positive plasma cells and self-sustaining inflammatory response. In this review, we focus especially upon the hepatopancreatobiliary system, autoimmune pancreatitis and IgG4-related sclerosing cholangitis. The cooperation of the gastroenterologist, radiologist, surgeon and histopathologist is crucial for establishing correct diagnoses and appropriate treatment, especially in IgG4 hepatopancreatobiliary diseases.

Imaging findings of IgG4-related hepatopathy: A rare case presenting as a hepatic mass

IgG4-related hepatopathy is usually referred to as parenchymal involvement of IgG4-related disease of the liver. As this disease entity was only recently described, little is known of its pathogenesis or imaging findings. We report a rare case of IgG4-related hepatopathy which presented as an ill-defined heterogeneously enhancing hepatic mass with diffusion restriction and a hepatobiliary phase defect in MR and CT images. Pathologic characteristics of the disease and its imaging findings are reviewed.

Recent advances in the concept and pathogenesis of IgG4-related disease in the hepato-bilio-pancreatic system

Recent studies have proposed nomenclatures of type 1 autoimmune pancreatitis (AIP) (IgG4-related pancreatitis), IgG4-related sclerosing cholangitis (IgG4-SC), IgG4-related cholecystitis, and IgG4-related hepatopathy as IgG4-related disease (IgG4-RD) in the hepato-bilio-pancreatic system. In IgG4-related hepatopathy, a novel concept of IgG4-related autoimmune hepatitis (AIH) with the same histopathological features as AIH has been proposed. Among organs involved in IgG4-RD, associations with pancreatic and biliary lesions are most frequently observed, supporting the novel concept of “biliary diseases with pancreatic counterparts.” Targets of type 1 AIP and IgG4-SC may be periductal glands around the bile and pancreatic ducts. Based on genetic backgrounds, innate and acquired immunity, Th2-dominant immune status, regulatory T (Treg) or B cells, and complement activation via a classical pathway may be involved in the development of IgG4-RD. Although the role of IgG4 remains unclear in IgG4-RD, IgG4-production is upregulated by interleukin 10 from Treg cells and by B cell activating factor from monocytes/basophils with stimulation of toll-like receptors/nucleotide-binding oligomerization domain-like receptors. Based on these findings, we have proposed a hypothesis for the development of IgG4-RD in the hepato-bilio-pancreatic system. Further studies are necessary to clarify the pathogenic mechanism of IgG4-RD.