Key Clinical MessageCytomegalovirus (CMV) ulcerations are rare clinical entities, but their occurrence is favored in immunocompromised patients who present a favorable environment for opportunistic infections. We describe the case of a patient treated for a systemic lupus erythematosus suffering from deep oral ulcerations. The case illustrates the complexity of establishing a precise etiological diagnosis of CMV lesions, as the diagnostic hypothesis can be varied: related to an immunodeficiency disorder or drug‐induced toxidermia.