Not paraneoplastic pemphigus but pemphigus vulgaris in a patient with thymoma.

To cite: Saraya T, Fujiwara M, Shimura C, et al. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/bcr-2015210433 DESCRIPTION A 54-year-old man with thymoma (figure 1A, arrow) diagnosed 8 months previously was referred to our hospital because of a 5-month history of painful oral ulcer and odynophagia. Physical examination showed erosion of the lips, pharynx, tongue and buccal mucosa (figure 1B, arrow), together with scrotal skin change (appearing similar to lichen planus; figure 1C, arrow heads) and scrotal erosion (figure 1C, arrow). On H&E staining, scrotum-biopsied specimens showed suprabasilar blisters with acantholysis (figure 1D, asterisk). On direct immunofluorescence, intercellular IgG and C3 deposits were noted, but not at the basement membrane. Indirect immunofluorescence studies of dilutions of the patient’s serum applied to a human skin substrate revealed circulating antibodies that bound to the intercellular regions (not to basement-membrane zones) of the epithelium at a titre of 1–160, whereas that applied to a rodent bladder substrate (negative control slides) did not. All serum antibodies to desmoplakin I and II, envoplakin and periplakin and desmoglein 1, were negative, but only serum desmoglein 3 antibody was positive on CLEIA (chemiluminescence enzyme immunoassay) (1:840) or ELISA (269.85). Therefore, the patient was diagnosed as not paraneoplastic pemphigus (PNP) but pemphigus vulgaris (PV). In PV, antibodies to desmosomal proteins are associated with the detachment of keratinocytes from one another (ie, acantholysis), Learning points