D3.258 - Not just a rash: a delayed diagnosis of allopurinol-induced dress syndrome

Background 

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) is a severe, potentially life-threatening drug-induced hypersensitivity reaction characterized by extensive cutaneous involvement, hematologic abnormalities and internal organ dysfunction. Allopurinol is one of the most frequently implicated drugs.

Case Presentation

We report the case of a 71-year-old female with chronic kidney disease, hypertension and anaemia, admitted to the Internal Medicine ward with a progressively worsening pruritic generalized rash lasting three week. During this time, she presented four times to the Emergency Department prior to hospitalization. Initial diagnoses included non-specific rash treated with topical corticosteroids and antihistamines and suspected scabies, despite lack of epidemiological context or clinical response. Only at the fourth presentation was she admitted for further investigation and an Allergy and Clinical Immunology consultation was requested. She had started treatment with allopurinol approximately two months before symptom onset and was the only recently introduced medication. On admission, the patient was febrile with diffuse erythematous and desquamative skin lesions with fissuring and loss of skin integrity, affecting the limbs, trunk and hands. Laboratory evaluation showed renal function deterioration with unremarkable urinary sediment, elevated inflammatory markers, marked eosinophilia (>1500/µL) and thrombocytosis. Based on clinical presentation, laboratory abnormalities and drug exposure, DRESS syndrome was suspected. The RegiSCAR score was 4, consistent with a probable diagnosis. Allopurinol was promptly discontinued. Infectious, autoimmune and hematologic causes were excluded. Systemic corticosteroid therapy was initiated, leading to progressive clinical and laboratory improvement, including normalization of eosinophil count and recovery of renal function. Skin biopsy later confirmed features compatible with drug-induced toxidermia. Allopurinol was permanently contraindicated.

Discussion/Conclusion

This case highlights the diagnostic challenges of DRESS syndrome and the risk of delayed diagnosis due to nonspecific presentation, often leading to repeated emergency visits. Early recognition and prompt withdrawal of the culprit drug are crucial to prevent severe organ involvement, particularly in patients with renal impairment. This case underscores the importance of clinical awareness, multidisciplinary management and long-term drug avoidance.