Trials
Research is also underway to evaluate the effect and safety of plasmablast-directed therapy with a monoclonal antibody (XmAb5871) which inhibits B-cell function without depleting these immune cells. XmAb5871 targets CD19 with its variable domain and has an Fc domain that has increased affinity to FcγRIIb. Epidemiology
As recognition of IgG4-RD is relatively recent, there are limited studies on its epidemiology. It is therefore difficult to make an accurate estimation of prevalence. Furthermore, age of onset is almost impossible to estimate; age at diagnosis is frequently misused as the age of onset. A 2011 study estimated the incidence of IgG4-RD in Japan at 2.8–10.8/million population, with a median age of onset of 58 years. Nomenclature
Prior to 2011, IgG4-RD used to get mentioned in the medical literature under various different names.At the 2011 International Symposium on IgG4-Related Diseases, the consensus name of IgG4-related disease was endorsed for the condition. This name had already been agreed upon as a consensus name among Japanese investigators, notably choosing not to use the term systemic as that might lead to malignant tumours in other organs getting incorrectly diagnosed as being just another manifestation of the IgG4-related condition.However, some experts at the international symposium did express reservations about naming the disease after IgG4, as its role in pathogenesis is questionable and the use of serum IgG4 concentrations as a biomarker is unreliable.An expanded term, Immunoglobulin G4-related disease, has sometimes been used also. However, this term was never referenced in the 2012 recommendations for nomenclature, and its use would appear to be erroneous.
Maintenance
Following a successful induction of remission, maintenance therapy might be given in some cases, for example when there is a high risk of relapse or in patients with organ-threatening manifestations. Common maintenance therapy is prednisolone 2.5–5 mg per day, or use of a steroid-sparing agent instead. Relapse
Relapses are common, and a previous history of relapse appears to be a strong predictor of future relapse. When relapse occurs while off therapy and there has been a prolonged disease remission following initial glucocorticoid induction, then the relapse can usually be managed successfully with a re-induction strategy using glucocorticoids. Introducing a steroid-sparing agent might also need to be considered for relapses; however, none has been tested in prospective, controlled studies, and evidence for their efficacy beyond that offered by concomitant glucocorticoid therapy is scarce.In one retrospective cohort study, baseline concentrations of serum IgG4, IgE and blood eosinophils were found to be independently predictive of relapse risk following treatment with rituximab with or without glucocorticoids; the higher the baseline values, the greater the relapse risk and the shorter the time to relapse. Other interventions
When organ involvement causes local mechanical problems, further organ-specific interventions may be necessary. For example, when a tumefactive lesion causes obstruction of the bile duct, it may be necessary to insert a biliary stent to allow the bile to drain freely. Similarly, ureteral or vascular stents, surgical resection or radiotherapy may be considered for various different presenting problems.