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Importance: Plasma cell orificial mucositis (PCOM) associated with cocaine use is an emerging, rare condition that has become a concern in Spain in recent years. Limited knowledge exists regarding this novel condition., Objectives: To delineate the clinicopathologic characteristics of this emerging entity and establish a novel approach in the differential diagnosis of cocaine-associated lesions., Design, Setting, and Participants: A descriptive, retrospective, multicenter case series of 10 patients diagnosed with cocaine-associated PCOM was conducted in Spain from April 2020 to March 2023., Main Outcomes and Measures: Patient demographic, clinical, histopathologic, and treatment data were collected., Results: A total of 10 patients (6 [60%] male; median [range] age, 45.5 [36-66] years) presenting with exudative ulcerated plaques were identified for this study. The lesions had raised and erythematous edges over the nostril and a median (range) evolution time of 9 (2-24) months. Septal or palate perforations were observed in 4 (40%) of the patients. Biopsies revealed a dense inflammatory infiltrate of plasma cells in the dermis without atypia and with eosinophils. All patients reported recent cocaine use. Three urine tests detected cocaine but found no presence of amphetamines or opiates. Six patients improved with corticosteroid therapy. Up to 60% of patients were lost to follow-up., Conclusions and Relevance: This case series describes the clinicopathologic characteristics of PCOM, an emerging entity associated with cocaine use in Spain, and demonstrates a novel approach in the differential diagnosis of cocaine-associated lesions. To date, cocaine-associated skin lesions have been reported as neutrophilic dermatoses and vasculitis. The appearance of a plasma cell infiltrate changes what has been described in the medical literature so far. PCOM is a benign condition of unknown cause characterized by a proliferative polyclonal plasma cell infiltrate. A comprehensive differential diagnosis workup is required to reach this exclusionary diagnosis. Several irritants have been documented in cases of PCOM, and a hypersensitivity mechanism has been proposed. Since the initial report of cocaine-associated PCOM in Spain, its incidence has experienced a surge in the country. The cause of this phenomenon may be attributed to newly unidentified adulterants. The administration of corticosteroids and discontinuation of cocaine use are the sole treatments that have demonstrated efficacy. Clinicians should be vigilant regarding this emerging condition and conduct inquiries into cocaine use. Additional research is required to clarify the pathophysiology of this emerging condition.

Competing Interests: Conflict of interest: the authors declare that they have no conflict of interest.