Development and Resolution of Cutaneous Lupus Erythematosus During Long-Term Pexidartinib Therapy

Abstract

Introduction Pexidartinib, an oral tyrosine kinase inhibitor targeting the CSF-1R pathway, is FDA-approved for treatment of tenosynovial giant cell tumor (TGCT). We describe a patient with recurrent pigmented villonodular synovitis (PVNS) who developed cutaneous lupus erythematosus (CLE) during long-term pexidartinib therapy. This is an adverse event not previously reported in the literature.

Case Report A 63 year-old woman presented to dermatology with a photosensitive rash involving the scalp, face, upper chest, and arms three years into treatment. Initial skin biopsy demonstrated dense lichenoid dermatitis with dermal mucin, and labs revealed a positive dsDNA antibody with negative ANA and ENA panel. The rash persisted despite moderate potency topical steroids, leading to a formal diagnosis of CLE. Her cutaneous symptoms responded to intensified topical therapy including clobetasol 0.05% solution, tacrolimus 0.1% ointment, and intralesional Kenalog injections. Four years after initiation of pexidartinib, hydroxychloroquine 200 mg twice daily was prescribed due to worsening joint pain and rising ANA titers. After one year of hydroxychloroquine therapy, her CLE showed near-complete resolution.

Discussion This case highlights that CLE, while potentially drug-associated, does not always necessitate cessation of essential systemic therapy. With appropriate dermatologic co-management, including topical corticosteroids and systemic immunomodulators, patients may experience major improvement without compromising oncologic care.