ORAL LICHENOID DRUG ERUPTION SECONDARY TO RITUXIMAB ADMINISTRATION

Abstract

<h3>Introduction</h3> Oral lichenoid drug eruption (OLDR) is an uncommon type of fixed drug eruption (FDE) rarely described following administration of rituximab. This case illustrates the importance of developing a broad differential diagnosis, encompassing delayed drug reactions, in immunocompromised patients presenting with oral lesions. <h3>Case Description</h3> A 64-year-old male with a past medical history of marginal zone lymphoma presented with fixed oral lesions following rituximab monotherapy. Two weeks following his second rituximab dose, he developed painful oral ulcers. Infectious workup was negative. Systemic lupus erythematosus (SLE) was considered given positive anti-nuclear antibody, double-stranded DNA, and low complement levels, as was paraneoplastic pemphigus, but antibody screen was negative. Given concern for oral lymphoma, a biopsy was performed and showed reactive squamous mucosa with ulcerative mucositis without evidence of lymphoma. Morphologic features suggested rituximab-induced ulcerative lichenoid drug reaction. He was started on oral and topical corticosteroids for 2 weeks, and his symptoms fully resolved. He was advised to avoid rituximab. <h3>Discussion</h3> FDE has rarely been described with rituximab, even rarer still is OLDR. Biopsy of the oral lesions was needed to suggest an OLRD secondary to rituximab. FDE can occur up to 2 weeks following drug administration, aligning with this patient's time course. Classically, symptoms resolve within 7-10 days following drug discontinuation. Oral lesions can be more persistent and last for months. Treatment involves a combination of drug discontinuation, oral, topical, and intralesional corticosteroids, depending on severity. This case highlights the importance of considering delayed drug reaction in patients with oral ulcers.