IgG4 (immunoglobulin G4) are antibodies of class G and represent the lowest proportion of IgG subclasses in the blood of healthy people. These are mainly formed in allergic reactions or increase with successful desensitization.
Due to the limited knowledge about the disease to date, the disease cannot currently be precisely attributed to autoimmune diseases or primary allergic reactions.
The first signs of the disease are usually inflammatory changes in the affected organ. As the disease progresses, connective tissue (fibrosis) multiplies at this point. The consequences are nodular changes, disturbances of organ functions and partly also pain in the corresponding tissue.
Because several organs can be affected simultaneously or consecutively, the signs of the disease can vary greatly and cannot be clearly defined. Some patients show general symptoms such as fever, sudden weight loss and night sweats. Other signs are often closely linked to the diseased organ and therefore cannot be standardised.
IgG4-associated disease is a rare differential diagnosis. Depending on the localization of the disease signs, the more frequent diseases of the respective organ are initially excluded. In this context, the possibility of a malignant disease, i.e. a tumour, must also be taken into consideration for certain findings.
Glucocorticoids, e.g. prednisolone, are primarily used for therapy, but there are still no precise recommendations as to the dosage and duration of therapy. Often a dose of prednisolone 40mg or 0.6mg/kg daily is prescribed at the start of treatment, which is gradually reduced over several months.