IgG4-related disease is an infrequent differential diagnosis. Depending on the localisation of symptoms
diseases of the respective organ must be excluded, as well as malignant
diseases, i.e tumors.
As with any disease, the overall picture consisting of clinical symptoms, laboratory
findings and imaging techniques (ultrasound, x-ray, computed tomopgraphy
and/or magnetic resonance imaging) needs to be evaluated. It should be noted that not only individual
clinical manifestations, limited to one organ exist, but rather further symptoms may occur
with involvement of other organs at the same time successively.
To establish a clear diagnosis, existing changes within the affected organ,
such as space-occupying lesions, inflammatory changes or fibrosis, need to
be examined carefully.
The most important diagnostic criteria for an IgG4-related disease is an appropriate histology. A special tissue staining
of the removed tissue material can make
a dense lymph plasmacellular infiltrate with classical increase of IgG4 positiv plasma cells (Ratio IgG4/IgG > 40%) visible.
Often a (storiform) fibrosis, occasionally an obliterative phlebitis can be
Often the IgG4 level is increased over normal value, but this is not
the case in every patient. However an increase of the IgG4 level can also occur
persons or patients with other diseases. Thus, the IgG4 level alone is neither evidence nor exclusion
of an IgG4-related disease.