A rare case of pemphigus vegetans with underlying diffuse large B-cell lymphoma

Pemphigus vegetans (PV) is one of the rarest variants of pemphigus, reported for only 1–2% of all pemphigus cases, which makes its diagnosis particularly challenging [1] . It classically presents with vegetative plaques involving intertriginous areas and the oral mucosa. Our patient presented with an atypical presentation, where, in addition to intertriginous verrucous lesions, she developed an exophytic/fungating lesion of the toe, a site not commonly reported in the literature. The pathophysiology of PV involves autoantibodies directed against desmoglein (Dsg) 3 and/or desmoglein (Dsg) 1, disrupting epidermal adhesion and leading to the characteristic clinical findings. The association between PV and diffuse large B-cell lymphoma (DLBCL) has been reported in only a handful of cases, and whether DLBCL acts as a triggering factor for PV remains unclear. In our patient, DLBCL recurrence was identified concurrently with the diagnosis of PV. This temporal relationship raises the question of whether the two conditions share a pathological link either as a coincidental autoimmune process or as a paraneoplastic manifestation. Diagnosis of PV is based on a combination of clinical features, histopathologic findings, and serologic evidence of antibodies against Dsg1 and/or Dsg3, confirmed by direct or indirect immunofluorescence [2] , [3] . Our patient met the diagnostic criteria for classic PV. The temporal correlation between DLBCL recurrence and the eruption of PV lesions further strengthens the argument for an association between the two conditions. Treatment of PV typically involves immunosuppressive agents, including corticosteroids, cyclophosphamide, azathioprine, dapsone, and mycophenolate, among others [4] , [5] , [6] . Given the potential association between DLBCL and PV in our patient, we pursued a unified treatment strategy using the R-CHOP regimen (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) to target the underlying lymphoma. The patient demonstrated a favorable response, with clearance of lesions in the intertriginous regions and the toe, lending further support to the hypothesis of a paraneoplastic relationship. This case presents a rare and instructive co-occurrence of PV and DLBCL recurrence. Although the patient met diagnostic criteria for PV, the clinical response to lymphoma-directed therapy suggests a meaningful underlying association. This case underscores the importance of recognizing atypical cutaneous presentations and rare pemphigus variants as potential indicators of an occult or recurrent hematological malignancy—a recognition that may significantly inform and streamline the treatment approach.