Clinical improvement of pemphigus-like mucocutaneous disease in a patient with CLL following initiation of zanubrutinib: a case report.

Pemphigus is an autoimmune bullous disease. PNP/PAMS represents a rare subtype of autoimmune bullous disease, and typically associated with an underlying neoplasm, particularly lymphoproliferative disorders. Current management of PNP primarily involves glucocorticoids, immunosuppressants, and rituximab. This article reports a 67-year-old male who presented with generalized erythema, blisters, and oral erosions with pain for one month. Initially diagnosed with pemphigus, he received methylprednisolone treatment, which led to slight improvement in skin lesions but minimal resolution of oral ulcers. Based on the available clinical, histopathological, immunofluorescence, and serological findings, the patient was initially diagnosed with pemphigus vulgaris in the setting of CLL. However, the refractory oral mucositis, dual positivity for Dsg1 and Dsg3, and the underlying B-cell malignancy raised the concern for paraneoplastic pemphigus (PNP). Given that PNP-specific tests-including anti-plakin antibodies, indirect immunofluorescence on rat bladder, and immunoblotting-were not performed, a definitive diagnosis of PNP could not be established. Therefore, the condition was managed as "suspected CLL-associated PNP" Following the initiation of zanubrutinib in combination with ongoing corticosteroid therapy and CLL treatment, significant improvement of oral erosions was observed. In this case, the clinical improvement may be potentially related to zanubrutinib, but the concurrent corticosteroid therapy and the control of CLL likely contributed as well. If zanubrutinib did play a role, the mechanism might involve enhanced disease control or immune modulation. However, the current evidence is insufficient to draw a firm conclusion, and its true efficacy needs to be evaluated in further studies.