DRESS Syndrome — SCE Dermatology MCQ

Correct answer: C — DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms)

The correct answer is C, DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms). The picture, a diffuse eruption 8 days after starting a new drug, facial oedema, fever above 38.5C, lymphadenopathy, marked eosinophilia, and hepatitis (ALT 340), maps onto the RegiSCAR scoring system, which awards points for fever, lymphadenopathy at two or more sites, eosinophilia, atypical lymphocytes, skin extent and facial oedema, internal organ involvement, and onset 2 to 8 weeks after drug exposure. Allopurinol is a classic high risk trigger for DRESS, particularly with renal impairment or the HLA-B*58:01 allele, and typically causes onset 2 to 6 weeks after starting treatment. Scoring this vignette against RegiSCAR yields a total in the definite or probable DRESS range, confirming the diagnosis over the other listed patterns. Why the other options are wrong: A. Viral exanthem: does not explain the temporal drug relationship, nor does it typically cause eosinophilia, facial oedema, or marked transaminitis. B. AGEP: presents within 1 to 2 days with sterile pustules on erythema and neutrophilia, not eosinophilia, lymphadenopathy, or hepatic involvement. E. Morbilliform drug eruption: is a simple exanthem without fever, facial oedema, eosinophilia, lymphadenopathy, or organ involvement; it is diagnosed by exclusion of systemic features. D. SJS/TEN: features mucosal erosions and epidermal detachment (positive Nikolsky sign) rather than facial oedema and eosinophilia, without this systemic organ pattern. Key point: Delayed onset (2 to 8 weeks), fever, facial oedema, lymphadenopathy, eosinophilia, and hepatic involvement after a high-risk drug like allopurinol scores as definite or probable DRESS on RegiSCAR, distinguishing it from AGEP, SJS/TEN, and simple exanthematous reactions.

Reference: DermNet NZ, Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), 2023, https://dermnetnz.org/topics/drug-reaction-with-eosinophilia-and-systemic-symptoms