VIDEO: IgG4-related disease is very ‘indolent’ autoimmune disease

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So, there are a number of things that set IgG4-related disease apart from other diseases. I suppose the chief characteristic really is that it is so indolent compared to many other autoimmune diseases or immune-mediated conditions. It is very, very slow moving, and by this, I mean that, typically, patients have had the disease for at least many months and often many years before they're diagnosed. And all this time, the disease is present, often in multiple organs, often causing nothing that is overt enough to lead the patient to medical attention, and this is dangerous because it's causing damage in those organs all the time.

Even pancreatitis, one of the most concerning manifestations of IgG4-related disease is very subclinical. Patients have relatively few symptoms, and this is very much counter to what we understand about pancreatitis in general. Pancreatitis caused by gallstones is intensely symptomatic, highly painful, and the same is true for alcoholic pancreatitis. But the pancreatitis associated with IgG4-related disease is often subclinical. And so, for many months or years, the pancreatitis can be destroying the pancreas. The upshot of this is by the time patients are diagnosed, a very high percentage of patients already have permanent damage in one or more organs. So, I think that is one thing that really does set this disease apart from most other immune-mediated diseases.

Another thing that is very characteristic of IgG4-related disease and important to mention is that the disease tends to cause masses, fibroinflammatory masses, tumor-like masses, in the organs that it affects. And a very high percentage of patients are actually misdiagnosed as having some type of cancer or another before the correct diagnosis is made. Many patients are subjected to radical surgical procedures, such as modified Whipple procedures in which most of the pancreas and other abdominal organs are removed. And so, this is another thing that's very important to understand about IgG4-related disease. Everything that is an indolent mass lesion is not necessarily a malignancy, and IgG4-related disease needs to be considered in that differential diagnosis.

A third thing that must be mentioned, given the name, IgG4-related disease, is that the great majority of patients with IgG4-related disease have very high elevations of serum IgG4, which is an antibody that we all have, but for reasons that remain imperfectly understood at the moment. In patients with IgG4-related disease, the serum IgG4 concentration is typically high and often very, very high. Example, elevated up to five or 10 times the upper limit of normal is not unusual in IgG4-related disease.

So those are the three things that I think I would highlight, the indolence, the tendency to cause mass lesions, and the elevations in serum IgG4 concentrations.