Severe Toxicodermia due to Apalutamide: A Case Report of DRESS in an Elderly Adult.

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) is a severe toxicoderma characterized by a hypersensitivity reaction to medications, accompanied by eosinophilia and systemic manifestations. Apalutamide, a selective androgen receptor inhibitor approved for the treatment of prostate cancer, has been associated with various dermatological complications. This study documents the clinical case of an 81-year-old geriatric patient with stage IV acinar adenocarcinoma of the prostate who developed toxicoderma four weeks after initiating apalutamide. The patient presented with a 15-day history of generalized papular lesions and malaise that did not improve with oral antihistamines. Physical examination revealed facial edema and erythema, along with desquamative erythematous-edematous plaques covering more than 50% of the body surface area. Laboratory findings showed eosinophilia (3040 cells/µL) and a rise in baseline creatinine from 1.76 mg/dL to 2.4 mg/dL. The RegiSCAR score was 3 points, classifying this as a possible case of DRESS. A skin biopsy demonstrated a dermoepidermal hypersensitivity reaction with eosinophilic infiltration. The patient improved with oral and topical corticosteroids and discontinuation of apalutamide, confirming the diagnosis of DRESS. He remains under follow-up by the Oncology service. Given that numerous medications have been implicated in DRESS syndrome, early recognition is critical. Prompt identification allows for the suspension of the causative agent, reducing morbidity and mortality. Furthermore, it facilitates timely modification of oncological therapy in advanced-stage patients, ensuring that cancer management is not compromised.