Sites where a diagnosis of IgG4-RD may be established without the requirement for all of the classical morphological features described elsewhere, especially storiform fibrosis
| Lymph nodes | Lymph nodes draining sites where ‘classical’ IgG4-related disease is present* 34 |
| Orbit | Dacroadenitis35 |
| Meninges | Chronic meningitis36 |
| Duodenum/ampulla of Vater | AIP/IgG4-related sclerosing cholangitis† 37 |
In these tissues, the histopathological diagnosis is most commonly based on a combination of dense lymphoplasmacytic inflammation and prominent IgG4+ plasma cells.
↵* A diagnosis of IgG4-RD in this setting would require additional criteria, for example, characteristic histopathological features within a tissue/organ associated with the lymph nodes.
↵† Biopsies from this area may provide useful supporting evidence for the presence of IgG4-RD but biopsies from the duodenum alone are unlikely to show all of the classical features: prominent IgG4+ plasma cells have been described in association with type 1 AIP.
AIP, autoimmune pancreatitis; IgG4-RD, immunoglobulin G subclass 4-related disease.