Severe cutaneous adverse reaction (SCAR) pathway

Recognizes DRESS, SJS/TEN, AGEP, and fixed drug eruption; documents drug causality with Naranjo; confirms DRESS with RegiSCAR; and applies SCORTEN/ABCD-10 for SJS/TEN mortality risk. Per the 2022 AAAAI Drug Allergy Practice Parameter.

Evidence tier: Guideline-derived.

Decision points

  • Classify the SCAR pattern

Do-not-miss pitfalls

  • Do not delay drug withdrawal, every hour the causative drug continues in DRESS or SJS/TEN worsens outcome.
  • Do not use systemic corticosteroids in SJS/TEN, most evidence shows harm (increased mortality, infection, delayed healing).
  • Do not label a DRESS as a "drug rash", DRESS has ~10% mortality and months-long organ sequelae.
  • Do not use silver sulfadiazine on SJS/TEN wounds, sulfadiazine is itself a SCAR-triggering sulfonamide.
  • Do not overlook cross-reactive aromatic anticonvulsants, carbamazepine, phenytoin, phenobarbital, and oxcarbazepine share the arene oxide metabolite and cross-react ≥40-80%.
  • DRESS with normal eosinophil count occurs, particularly vancomycin-associated DRESS. Do not exclude on eosinophil count alone.
  • Long-term DRESS sequelae: hypothyroidism (up to 20%), type 1 diabetes, end-organ fibrosis, follow for at least 6-12 months.
  • Generalized bullous FDE (GBFDE) can mimic SJS/TEN, distinguish by site-fidelity (same anatomical location with each exposure) and Nikolsky-negative uninvolved skin.

Evidence & citations

  1. Khan DA, Banerji A, Blumenthal KG, et al. Drug allergy: A 2022 practice parameter update. J Allergy Clin Immunol. 2022;150(6):1333-1393. PMID 36122788
  2. Bastuji-Garin S, Fouchard N, Bertocchi M, et al. SCORTEN: a severity-of-illness score for toxic epidermal necrolysis. J Invest Dermatol. 2000;115(2):149-153. PMID 10951229
  3. Kardaun SH, Sekula P, Valeyrie-Allanore L, et al. Drug reaction with eosinophilia and systemic symptoms (DRESS): an original multisystem adverse drug reaction. Results from the prospective RegiSCAR study. Br J Dermatol. 2013;169(5):1071-1080. PMID 23855313
  4. Duong TA, Valeyrie-Allanore L, Wolkenstein P, Chosidow O. Severe cutaneous adverse reactions to drugs. Lancet. 2017;390(10106):1996-2011. PMID 28476287

Clinician decision support. Verify against the cited source. Not a substitute for clinical judgment. 100% on-device; no patient data is stored or transmitted.