The diagnosis IgG4-related disease (IgG4-RD) is often difficult to make. The clinical spectrum is diverse, with a variety of organ systems that may be affected simultaneously or sequentially. Patients often present with symptoms that mimic a malignant disease, for example, symptoms compatible with a pancreatic tumour. The lack of reliable tests often prolongs the diagnostic process. Limited insight into the causative disease mechanisms has confined the therapeutic options to the empirical use of immunosuppression. During the past year, the first papers on the fundamental aspects of the disease have resulted in the emergence of a new disease model for IgG4-RD. Recently published clinical and experimental findings support the hypothesis that antigenic stimulation plays a pivotal role in the aetiology of IgG4-RD. These new insights may pave the way for more sensitive diagnostic tests and more evidence-based strategies to cope with the many manifestations of IgG4-related disease.