Here are some key issues addressed in a recent review.
What are some of the IgG4 related diseases?
These may coexist in the same patient:
Autoimmune pancreatitis type 1
Mikulicz disease (salivary gland infiltration)
Coronary artery aneurysm
Inflammatory abdominal aortic aneurysm (and the related condition retroperitoneal fibrosis)
Riedel's thyroiditis (and other forms of thyroid involvement)
Pulmonary mass or interstitial disease
Lymphadenopathy (Castleman like and other forms)
Sclerosing cholangitis (which differs in some features from primary sclerosing cholangitis)
How is IgG4-RD diagnosed?
This has been in a state of some controversy and flux. From the article:
According to an international symposium held in 2011, the diagnosis of IgG4-RD requires both an appropriate histological appearance and increased numbers of IgG4-positive plasma cells (or an elevated IgG4:IgG ratio) in tissue...
In 2011, an “All Japan IgG4 Team,” with the aim to draft comprehensive diagnostic criteria for IgG4-RD 51 ( Table 3 ), proposed three major items 51 69 (1) single or multiple organs involved with diffuse or localized swelling, masses, nodules, and/or hypertrophic lesions; (2) elevated serum IgG4 levels (greater than or equal to 135 mg/dL); and (3) histopathologic features that include marked lymphocytic and plasma cell infiltration and fibrosis, with IgG4-positive plasma cell infiltration (IgG4/IgG-positive cell ratio of greater than or equal to 40% and IgG4-positive plasma cells exceeding 10/HPF). Based on these criteria, patients can be classified into the categories of definite, probable, or possible IgG4-RD.
How do autoimmune pancreatitis (AP) types 1 and 2 differ?
Age: older onset (6th decade) typical of type 1
Gender: male predominance in type 1, not 2
Relationship to IgG4: present in type 1, not clearly present in 2
Histology: lymphoplasmacytic sclerosing pancreatitis in type 1, idiopathic duct centric pancreatitis in 2
Abdominal pain: common in type 2, not in 1
Other organ involvement common in 1, not 2
Steroid responsiveness characterizes both types but type 1 is more prone to relapse.