IgG4-related disease (IgG4-RD) is a complex multi-system inflammatory disorder that can affect various organs in the body. This condition is characterized by elevated levels of immunoglobulin G subclass 4 (IgG4) and the presence of specific histopathological features. While neurological involvement is not as common as in other organs, when it occurs, it can lead to hypertrophic pachymeningitis and hypophysitis. Here, we present a case of a 53-year-old male with right-sided hemicranial headache and diplopia. Computed tomography revealed a soft tissue density lesion in the middle ear cavity and mastoid antrum with the destruction of the mastoid septae. Magnetic resonance imaging revealed a lesion in the right middle ear cavity associated with pachymeningitis and right sigmoid and transverse sinus thrombosis. Tissue pathology revealed dense plasma cell-rich chronic inflammation with storiform fibrosis. Immunohistochemistry was positive for IgG4. Hence, a diagnosis of IgG4-related disease causing mastoiditis, pachymeningitis and cerebral venous thrombosis was made. The patient was successfully operated and treated with steroids. IgG4-RD remains a rare but serious condition. It is crucial to identify and treat this condition promptly as it can lead to permanent organ damage. When patients continue to experience middle ear symptoms after an infection has been treated and cancer has been ruled out, it is important to consider inflammatory conditions as a differential diagnosis.

Immunoglobulin G4-related disease (IgG4-RD) is a systemic condition known to affect multiple organ systems. While its manifestations are diverse, pulmonary involvement, especially of the pleura, remains less common. We report the case of a 99-year-old Saudi male with a medical history of diabetes mellitus, chronic kidney disease, and hypertension. He presented with dyspnea and syncope, with radiological findings revealing pleural effusion and a mass in the right hemidiaphragm. Laboratory investigations highlighted elevated serum IgG4 levels, and histopathological evaluation confirmed the diagnosis of IgG4-RD. Notably, the patient\'s thoracic histopathology differed from typical IgG4-RD presentations, emphasizing the variability of the disease. This case underscores the significance of recognizing IgG4-RD as a potential cause of unexplained pleural effusion. It also highlights the need for a comprehensive diagnostic approach, integrating laboratory values, histopathological findings, and clinical context. Given the potential variability in thoracic IgG4-RD histopathology, clinicians should maintain a heightened awareness of this condition to avoid missed diagnoses.

Immunoglobulin G4-related disease (IgG4-RD) is a unique immunological disease that can impact multiple organs including a formation of a hepatic inflammatory pseudotumor (IPT). We present a case of a 67-year-old male with a history of chronic viral hepatitis C infection who had an accidental finding on magnetic resonance imaging (MRI) of a liver arterially enhancing lesion. With an extensive work-up, immunohistochemical stains for immunoglobulin G of the liver lesion was performed and showed markedly increased IgG4-positive plasma cells (> 50/HPF), which was consistent with hepatic inflammatory pseudotumor related to IgG4-RD. The patient was treated with prednisone with a complete resolution of the hepatic lesion. The diagnosis of hepatic IPT and IgG4-RD requires a high degree of clinical suspicion and coordination with a multi-disciplinary team, including pathologists. Early tissue acquisition and staining for IgG4 was essential for the early diagnosis and treatment in this case. We also provide a comprehensive summary of published reports of IgG4-RD presenting with IPT.

This case report describes a 55-year-old male who presented with a two-year history of abdominal pain and weight loss, along with recent onset nausea, vomiting, and anorexia. Laboratory tests revealed elevated serum IgG4 levels and anemia, and abdominal CT showed diffuse pancreatic enlargement and multiple retroperitoneal lymphadenopathy. Endoscopic ultrasound-guided fine-needle aspiration of the pancreatic mass revealed dense lymphoplasmacytic infiltration with fibrosis and increased numbers of IgG4-positive plasma cells, consistent with the diagnosis of IgG4-related pancreatitis. Treatment with prednisone led to a significant improvement in the patient\'s symptoms and laboratory values, with subsequent reduction in the size of the pancreatic mass and retroperitoneal lymphadenopathy. The patient remained asymptomatic at the six-month follow-up visit, and serum IgG4 levels remained within the normal range. This case highlights the importance of considering IgG4-related disease (IgG4-RD) in patients presenting with abdominal pain and weight loss and the potential effectiveness of corticosteroid therapy in managing this condition.

IgG4 related disease (IgG4-RD) is a rare, immune-mediated inflammatory disease that varies widely in its presentation because it can affect nearly any organ. We present a case of a 73-year-old male who presented with an ill-defined mass of the parotid gland, found to be IgG4-RD, after several months of work up and tissue sampling. Most cases of salivary gland involvement in IgG4-RD present as bilateral swelling of the submandibular glands. We present this case as a unique manifestation of salivary gland disease in IgG4-RD as a persistent, non-discrete unilateral mass in the parotid gland. It is critical that clinicians who regularly treat salivary gland pathologies are familiar with this rare disease and its potential manifestations in the oral cavity.

Immunoglobulin G4-related disease (IgG4 RD) has a fair prognosis but its diagnosis has been difficult due to the condition\'s wide range of clinical manifestations, limited awareness among common practitioners, and various differentials. Here, we present a case of an elderly male who presented with recurrent dental caries, recurrent sinusitis, persistent dry mouth, and dry eyes along with bilateral parotid gland enlargement without any lymphadenopathy. The patient was evaluated further and found to have elevated levels of IgG4 and on histopathological examination of the parotid gland showed lymphocytic infiltrate with germinal centers without any granulomatous lesions and IgG4-positive plasma cells on immunohistochemistry (IHC). The patient was diagnosed with IgG4 RD and was started on corticosteroids, after which there was a symptomatic improvement.

Immunoglobulin G4-related disease (IgG4-RD) is a rare immune-mediated disease affecting multiple organs and tissues. There is often the presence of elevated serum Ig4 subtype with histological evidence of lymphoplasmacytic infiltration, fibrosis, and phlebitis. The mainstay of treatment is steroids therapy. We report the case of a 66-year-old man presenting with acute on chronic renal failure and pulmonary nodules seen on PET-CT scan. He also had elevated serum IgG4 subclass and histological features in keeping with IgG4-RD. He failed steroid therapy but responded subsequently to rituximab with complete resolution of his symptoms.