Oral plasma cell mucositis: a series of 3 cases with a focus on screening for systemic IgG4 disease

Abstract

Plasma cell mucositis (PCM) is an idiopathic generalized oral inflammatory condition with no consensus on optimal treatment strategy. Hypersensitivity may account for some cases, but etiology and causative factors mostly remain unknown. While more commonly associated with salivary gland involvement, systemic IgG4 disease may manifest as PCM. The reliability and calibration of IgG4 immunohistochemistry (IHC) or serum IgG4 testing for diagnosis of PCM remains uncertain. We present a series of three cases of oral PCM demonstrating the challenges in screening and management of this condition. The cases involved 71, 80, and 70-year-old males respectively. All cases initially affected the gingiva but spread to adjacent mucosa appearing as diffusely erythematous and edematous areas with superficial ulceration. Case 1 also reported a history of pancreatitis, and Case 3 reported sicca symptoms along with history of pancreatic and thyroid disease. Microscopically plasma cell mucositis was confirmed with all cases demonstrating polyclonality on kappa/lambda testing. Cases 1 and 3 also showed fibrinogen positivity on concurrent direct immunofluorescence testing, with Case 2 being negative. Cases 1 and 2 demonstrated more than 10 IgG4 cells per high power field on IHC testing, and Case 3 was unavailable for IHC testing. Case 1 was eventually diagnosed with systemic IgG4 disease after serum testing, and Cases 2 and 3 showed normal serum IgG4 testing results. None of the cases reported associated hypersensitivity to foods or oral care products. Cases 1 and 2 and were unresponsive to topical and systemic steroids, topical calcineurin inhibitors, and doxycycline. Case 3 was unresponsive to topical steroids and methotrexate. Case 1 eventually improved with rituximab, Case 2 remained stable, and Case 3 was treated partially successfully with mycophenolate. Full resolution was not achieved in any case. These cases demonstrate the need for additional consensus of best practice screening and treatment methods in PCM.