According to a new concept for the classification and division of autoimmune diseases, Mikulicz\'s disease and Küttner\'s tumor belong to immunoglobulin G4-related diseases (IgG4-RD) and fulfil their diagnostic criteria. The aim of this study was to summarize the new classification concepts of IgG4-RD in the head and neck area and to review their clinical, histopathological and serologic criteria and the methods used in the diagnostic workup with respect to their advantages, limitations and differentiative value. The PubMed, Web of Science, Google Scholar, and Scopus databases were searched for articles published between 2009 and 2019 using the following key words: IgG4-related diseases, Mikulicz\'s disease, Küttner\'s tumor, salivary glands, xerostomia. Results of the review of the literature revealed that Mikulicz\'s disease and Küttner\'s tumor fulfil the same diagnostic criteria but may manifest different clinical symptoms which determine the choice of the different diagnostic tools.

Mikulicz\'s disease (MD), an immunoglobulin G4 (IgG4)-related disease, is a fibrosis-associated inflammatory disease characterized by painless bilat- eral swelling of lacrimal and salivary glands. Although thrombocytopenia is associated with many rheumatologic disorders, it is rare in IgG4-related MD. This novel study aims to report a rare case of IgG4-related MD complicated with severe autoimmune thrombocytopenia without any hemato- logical malignancies and review all cases of IgG4-related disease associated with thrombocytopenia in the literature.