Plasma cell mucositis (PCM) is an unusual disorder most evident in the accessible mucosa and usually reported in the upper aerodigestive tract, although it is named according to its specific anatomical site of involvement, such as plasma cell cheilitis, plasma cell gingivitis, plasma cell vulvitis, and Zoon's balanitis. PCM reflects a dense polyclonal, rather than a monoclonal, plasma cell proliferation of unclear and unknown etiology. This perplexing disorder tends to be treated by avoiding possible triggers and intralesional and/or systemic steroids. Herein we review and provide an update on PCM, which often represents a clinical conundrum.