Differential Diagnosis for Elevated Serum IgG4

Elevated serum IgG4 levels can be associated with various conditions. Here's a differential diagnosis organized into categories:

• Single Most Likely Diagnosis

  • IgG4-Related Disease (IgG4-RD): This is a fibroinflammatory condition characterized by tumor-like swelling of affected organs, infiltration of IgG4-positive plasma cells, and variable degrees of fibrosis. Elevated serum IgG4 levels are a hallmark of this disease, although not all patients with IgG4-RD have elevated IgG4 levels.

• Other Likely Diagnoses

  • Multifocal Fibrosclerosis: This condition is closely related to IgG4-RD and involves fibrosis and inflammation in multiple organs, often with elevated IgG4 levels.
  • Sjögren's Syndrome: Some patients with Sjögren's syndrome, an autoimmune disorder that primarily affects the glands that produce tears and saliva, may have elevated IgG4 levels.
  • Chronic Sclerosing Sialadenitis (Kuttner Tumor): This is a condition that affects the salivary glands and can be associated with elevated IgG4 levels.

• Do Not Miss Diagnoses

  • Lymphoma: Certain types of lymphoma, such as follicular lymphoma or marginal zone lymphoma, can present with elevated IgG4 levels. Missing this diagnosis could have significant implications for treatment and prognosis.
  • Sarcoidosis: Although less common, some cases of sarcoidosis, an inflammatory disease that affects multiple organs, can present with elevated IgG4 levels.

• Rare Diagnoses

  • Hyper-IgG4 Syndrome: A rare condition characterized by recurrent infections, elevated IgG4 levels, and eczema.
  • Good’s Syndrome: A rare immunodeficiency disorder that can present with elevated IgG4 levels among other immunoglobulin abnormalities.
  • Castleman Disease: A rare disorder that involves an overgrowth of cells in the body's lymph nodes, which can sometimes be associated with elevated IgG4 levels.

Each of these conditions has distinct clinical features, and the diagnosis of elevated serum IgG4 should be considered in the context of the patient's overall clinical presentation, imaging findings, and histopathological examination.