100496 - Multiple fixed medicamentous rash attributable to Oxaliplatin

Fixed drug eruption (FDE) is linked to over 100 pharmacological agents. This condition is characterized by lesions that consistently manifest in identical locations following exposure to the same therapeutic agent. The primary intervention involves the identification of the causative medication and its subsequent discontinuation. The predominant variant of FDE is localized, presenting as a self-limiting lesion; although the offending drug can be validated through oral provocation, such an approach is inadvisable due to the potential for severe or even generalized adverse reactions. The proposed investigation entails the administration of a patch test at the site of lesion manifestation.

A 61-year-old male patient with a medical history of medial rectal adenocarcinoma CT4bn2am0 has undergone chemotherapy (Oxaliplatin and Capecitabine) until the year 2022. He was subsequently referred to allergy clinics following a recurrence of the tumor located in the middle rectum, necessitating renewed treatment with oxaliplatin. Two hours subsequent to oxaliplatin infusion, the patient experiences palmoplantar pruritus, which is followed by the development of purplish plaques on both feet (Figure 1). The pruritus subsides within hours, yet residual hyperpigmented lesions with pruritic characteristics persist.

We conducted skin testing (prick and intradermal) with oxaliplatin, followed by delayed readings, which revealed a reactivation of the plaques on both feet at 7-8 hours post-testing. We conferred with the oncology department and the patient to evaluate the risk-benefit ratio associated with the continuation of oxaliplatin cycles, resulting in a consensus to proceed cautiously with the remaining four cycles of treatment. The patient exhibited identical symptoms half an hour subsequent to the conclusion of each cycle, without any escalation in the intensity or severity of the lesions.

FDE represents a late CD8 T cell-mediated reaction, diagnosed via detailed medical history and epicutaneous testing. Although drug provocation is the diagnostic gold standard, it carries risks of recurrence of symptoms. Management entails avoidance of the culprit drug, weighing the therapeutic benefits against risks. Given the delayed nature of these reactions, preemptive measures with antihistamines and corticosteroids are not warranted. In this instance, the patient tolerated ongoing oxaliplatin treatment, leading to a multidisciplinary consensus to persist with close observation.