Arezou Khosroshahi

To summarize the existing knowledge of various clinical presentations of IgG4-related systemic disease (IgG4-RSD) and to review the evolving list of organs affected by IgG4-RSD. The term IgG4-RSD encompasses a variety of clinical entities once regarded as being entirely separate diseases. The list of organs associated with this condition is growing steadily. Tissue biopsies reveal striking histopathological similarity, regardless of which organ is involved, although subtle differences across organs exist. Diffuse lymphoplasmacytic infiltrates, presence of abundant IgG4-positive plasma cells and extensive fibrosis are the hallmark pathology findings. Tumorous swelling, eosinophilia, and obliterative phlebitis are other frequently observed features. Polyclonal elevations of serum IgG4 are found in most but not all patients. IgG4-RSD is an underrecognized condition about which knowledge is now growing rapidly. Yet there remain many unknowns with regard to its cause, pathogenesis, various clinical presentations, approach to treatment, disease monitoring, and long-term outcomes. A wide variety of organs can be involved in IgG4-RSD. Clinicians should be aware of this entity and consider the diagnosis in the appropriate settings.

Purpose of review IgG4-related systemic disease (IgG4-RSD) is a systemic fibroinflammatory condition that can affect any organ system. Prompt recognition and management of this disease process are necessary to prevent sclerosis and permanent organ damage. Here, we review the advances in treatment approaches to IgG4-RSD. Recent findings Most information regarding treatment is derived from retrospective case series of patients with autoimmune pancreatitis (AIP), and follow-up periods have generally been short. A variety of IgG4-RSD presentations respond rapidly to glucocorticoid treatment. Glucocorticoids have become a standard therapy for AIP, but the indications requiring treatment as well as the appropriate starting dose and duration of therapy remain controversial. The importance of maintenance of glucocorticoids following remission induction is debatable. As our knowledge grows regarding other organ manifestations of IgG4-RSD with longer follow-ups, the necessity of steroid-sparing agents to manage frequent relapses becomes clear. Summary The natural history and long-term prognosis of IgG4-RSD are not well understood. Large prospective studies and randomized controlled trials of patients with wide spectrum manifestations of IgG4-RSD are required to support better approaches to treatment.