Clinical manifestations are variable depending on the organ system involved. Most commonly, IgG4-RD is associated with autoimmune pancreatitis (see chronic pancreatitis), a rare, chronic disease with varied presentation, often mimicking pancreatic malignancy, making diagnosis challenging. Autoantibodies in the pancreas cause inflammation and enlargement. Other manifestations include lymphadenopathy, biliary obstruction (may present similarly to primary sclerosing cholangitis), membranous nephropathy, salivary dysfunction, lacrimal gland dysfunction, retroperitoneal fibrosis, coronary arteritis, cutaneous plaques on the head and neck, and atopy (asthma, eczema), etc, although nearly any organ system can be affected. Symptoms typically develop over months to years, and treatment success is variable.
Proposed diagnostic criteria include:
- Clinical examination shows characteristic diffuse / localized swelling or masses in single or multiple organs.
- Hematological examination shows elevated serum IgG4 concentrations (135 mg/dL).
- Histopathologic examination shows:
- Marked lymphocyte and plasmacyte infiltration and fibrosis.
- Infiltration of IgG4+ plasma cells: ratio of IgG4+ / IgG+ cells > 40% and > 10 IgG4+ plasma cells per high-power field.