Comment on article: ‘Dupilumab as a novel steroid-sparing treatment for IgG4-related disease’ by Simpson et al

We read with interest the letter by Simpson et al reporting the use of dupilumab in a patient with IgG4-related disease (IgG4-RD).1 Indeed blocking the IL-4/IL-13 pathway is tempting, considering the roles of these cytokines and the physiopathological changes observed during IgG4-RD.2 3\n\nWe have also treated with dupilumab a 51-year-old man with IgG4-related dacryoadenitis and sialadenitis (bilateral lacrimal, parotid, sublingual and submandibular involvement, pattern of Mikulicz syndrome). Left submandibular salivary gland and two cervical lymph nodes biopsies concluded, respectively, to lymphoplasmacytic polyclonal infiltration and reactive hyperplasia. Immunohistochemistry was only available on lymph nodes, showing an IgG4+/CD138+ plasma cells ratio over 40% with 40 IgG4+ plasma cells/high power field. Serum IgG4 and IgE levels were found to be 17.7 g/L (normal range \u003c0.8 g/L) and 3499 kIU/L (normal range \u003c100 kIU/L), respectively, with normal complete blood count, liver and renal function tests. According to the 2019 American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-RD, entry criteria were met, …