IgG4-related disease

Abstract Immunoglobulin (Ig) G4-related disease is an immune-mediated fibro-inflammatory condition that can involve virtually every organ system. Our knowledge and understanding of this condition has expanded rapidly over the last decade, with insights into adaptive and innate immunological mechanisms, identification of novel risk factors, definition of disease subsets based on organ distribution, discovery of circulating biomarkers that correlate with disease activity and relapse, and novel treatment approaches. However, many challenges remain. The diagnostic work-up remains complex, requiring a combination of clinical examination, serology, imaging and histological evaluation with cross-speciality input. This requires the exclusion of a broad variety of differential diagnoses. Treatment often dampens inflammation, although relapse remains common on tapering or discontinuation of best available immunosuppression. Progressive fibrosclerotic disease and an increased risk of malignancy are recognized outcomes.