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derm.drug-eruption.core.v1PRODUCTION
derm.drug-eruption.core.v1

Cutaneous drug eruption — morbilliform vs SCAR (dermatology lens)

dermatologyacutesubacuteadultpediatric
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12/12 authored

Canonical 12-phase frame with authored status for this dossier.

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Frame

Detailed

Frame the cutaneous drug-eruption SPECTRUM and the central triage question: benign simple morbilliform/exanthematous (~90%) vs life-threatening SCAR. STOP/identify the culprit drug is the universal cornerstone across every branch. SJS/TEN is recognised here and ROUTED to derm.sjs-ten.core.v1 (managed there, not re-authored). Anaphylactic/urticarial drug reactions route to allergy.anaphylaxis.v1 / derm.urticaria.core.v1.

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spectrum + triage frame set; SJS/TEN + anaphylaxis routing-out scope declared

Patient inputs (17)

Complete drug list with start/stop dates is the spine of causality — latency window (4–14 d morbilliform/SJS-TEN, 2–8 wk DRESS, <4 d AGEP) plus ALDEN scoring identifies the single most-probable culprit (Sassolas ALDEN PMID 20375998; Kardaun RegiSCAR PMID 23855313)

High fever (≥38.5 °C) on an exanthem raises the SCAR prior — a RegiSCAR/AGEP/SJS-TEN systemic-severity variable; afebrile isolated morbilliform favours benign (Kardaun RegiSCAR PMID 23855313; Halevy PMID 19458527)

Pediatric drug rash overlaps Mycoplasma/viral exanthem & MIRM; weight-band dosing; geriatric polypharmacy makes culprit attribution harder (Wei/Nelson JAAD 2023 Part I PMID 37516359)

≥2 mucosal sites with erosion is a SJS/TEN-defining feature and a hard escalation trigger off a morbilliform background — mucositis pivots benign → SCAR (Wei/Nelson JAAD 2023 Part II PMID 37516356; Parvathaneni PMID 40541663)

Skin pain/tenderness, dusky/targetoid colour, blisters, or a positive Nikolsky sign signal epidermal necrosis (SJS/TEN) — never simple morbilliform (Parvathaneni Ocul Surf 2025 PMID 40541663)

Facial/periorbital edema + lymphadenopathy on a 2–8 wk-latency exanthem is a cardinal DRESS feature (RegiSCAR score) (Kardaun RegiSCAR PMID 23855313)

Hypotension/airway compromise → anaphylactic/urticarial drug reaction or septic SCAR — route anaphylaxis / sepsis pathway (Balakirski PMID 28412864)

Transient (<24 h/lesion) wheals ± angio-oedema/throat tightness/wheeze indicate an urticarial/anaphylactic drug reaction — a different mechanism + pathway than morbilliform/SCAR (Balakirski PMID 28412864)

Dozens of sterile non-follicular pinhead pustules on edematous erythema, rapid onset, flexural accentuation → AGEP (EuroSCAR validation) (Halevy PMID 19458527)

Prior SCAR or prior reaction to the culprit class mandates never-re-expose and informs ALDEN/causality (Sassolas ALDEN PMID 20375998)

HLA-B*15:02 (carbamazepine/aromatic AED SJS-TEN), HLA-B*58:01 (allopurinol SCAR), HLA-A*31:01 (carbamazepine MPE/DRESS/SJS-TEN) — pre-prescription screening + lifelong avoidance (Hung PMID 15743917; McCormack PMID 21428769; CPIC PMID 29392710)

HIV raises sulfonamide/antiretroviral drug-eruption + SCAR risk markedly; alters culprit prior and threshold (Balakirski PMID 28412864)

Peripheral eosinophilia (>0.7×10⁹/L, hallmark >1.5×10⁹/L) is a core DRESS RegiSCAR variable and a morbilliform→SCAR escalation flag (Kardaun RegiSCAR PMID 23855313)

Transaminitis (ALT >2× ULN) or cholestasis = DRESS visceral organ involvement (RegiSCAR) and gates steroid duration/taper (Kardaun RegiSCAR PMID 23855313; Wei/Nelson JAAD 2023 Part II PMID 37516356)

AKI is DRESS renal organ involvement and a SCAR severity marker; gates cyclosporine and informs CKD-EPI 2021 dosing (Wei/Nelson JAAD 2023 Part II PMID 37516356)

Neutrophilia favours AGEP; atypical lymphocytes + eosinophilia favour DRESS; baseline for infection surveillance (Halevy PMID 19458527; Kardaun RegiSCAR PMID 23855313)

Gates SCAR therapy — cyclosporine acceptable in DRESS; systemic-steroid risk/benefit; antihistamine selection in pregnancy (Wei/Nelson JAAD 2023 Part II PMID 37516356)

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (8)

8 need judgement
  • informationallife_threateningsjs_ten_features_route_out
    Skin pain/tenderness, dusky/targetoid lesions, blisters, positive Nikolsky, or ≥2-site mucosal erosion on a drug-linked eruption (Parvathaneni Ocul Surf 2025 PMID 40541663)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningdress_facial_edema_eosinophilia_organ
    Facial/periorbital edema + eosinophilia (>1.5×10⁹/L) + 2–8 wk latency + lymphadenopathy + hepatitis/AKI on a morbilliform background — RegiSCAR probable/definite DRESS (Kardaun RegiSCAR PMID 23855313)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateninganaphylactic_or_urticarial_drug_reaction
    Drug-linked transient wheals/angio-oedema with throat tightness, wheeze, or hypotension (Balakirski PMID 28412864)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseveremorbilliform_that_may_be_early_scar
    A morbilliform eruption PLUS any single SCAR red flag — mucosal involvement, facial edema, fever ≥38.5 °C, skin pain, eosinophilia, or organ derangement (Wei/Nelson JAAD 2023 Part II PMID 37516356)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverehigh_risk_culprit_or_hla_match
    Culprit is allopurinol / aromatic anticonvulsant / sulfonamide / vancomycin / NSAID / immune-checkpoint inhibitor, OR HLA-B*15:02 / HLA-B*58:01 / HLA-A*31:01 positive (Hung PMID 15743917; McCormack PMID 21428769; CPIC PMID 29392710)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalmoderateagep_sterile_pustules_neutrophilia
    Dozens of small sterile non-follicular pustules on edematous erythema, flexural accentuation, fever, neutrophilia, rapid onset (<2 wk, often <4 d) (Halevy PMID 19458527)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalmoderatepediatric_drug_rash_vs_mycoplasma_or_viral
    Child with an exanthem ± mucositis where a clear drug timeline is absent — Mycoplasma-induced rash and mucositis (MIRM) or viral exanthem can mimic a drug eruption (Wei/Nelson JAAD 2023 Part I PMID 37516359)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalmildrecurrent_same_site_fixed_drug_eruption
    Solitary/few well-demarcated round dusky/violaceous plaques recurring at the IDENTICAL site within hours–2 d of re-exposure to the same drug (Balakirski PMID 28412864)
    Trigger could not be auto-evaluated — needs clinician judgement.

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Recommended regimen

Cutaneous drug eruption — STOP-culprit-first + phenotype-stratified ladder (RegiSCAR / JAAD 2023 / ALDEN)
axis: drug_eruption_culprit_first_ladderstep 1 - Step 1 — STOP / identify the culprit drug (universal, every phenotype)
Selected step "Step 1 — STOP / identify the culprit drug (universal, every phenotype)" — EVERY drug eruption, day 0 — the single highest-impact intervention across benign morbilliform AND every SCAR
  • discontinue probable culprit + all non-essential cross-reactors
    first line
    culprit_withdrawal
    n/a
    Sassolas ALDEN (PMID 20375998) + Wei/Nelson JAAD 2023 Part II (PMID 37516356) — identify the single most-probable culprit by latency window + ALDEN logic and stop it (plus cross-reactors); withdrawal is the universal cornerstone and, for SCAR, the dominant survival lever.
  • allergy-record + lifelong culprit/cross-reactor avoidance documentation
    first line
    decision_gate
    n/a
    Wei/Nelson JAAD 2023 Part II (PMID 37516356) — document the suspected culprit class + cross-reactors in the allergy record before disposition; never re-challenge a SCAR culprit (Sassolas ALDEN PMID 20375998).
  • defined-scenario treat-through decision gate (benign morbilliform only)
    rescue
    decision_gate
    triggers: essential_non_substitutable_drug, mild_isolated_morbilliform, no_scar_features, close_monitoring_available
    Wei/Nelson JAAD 2023 Part I (PMID 37516359) — "treat-through" is acceptable ONLY for a mild isolated morbilliform eruption to an essential non-substitutable drug with NO SCAR features and close surveillance; any SCAR feature voids this gate.

outpatient playbook — drug actions (3)

  1. 1. STOP probable culprit + non-essential cross-reactors
    n/a • n/a • immediate
    trigger: Any drug-linked eruption (Sassolas ALDEN PMID 20375998)
    Universal cornerstone; for SCAR the dominant survival lever
  2. 2. triamcinolone 0.1% topical (symptomatic)
    rxcui 10759
    0.1% • topical • BID until settled
    trigger: Pruritic benign morbilliform eruption (Balakirski PMID 28412864)
    Symptomatic relief while culprit washes out; self-limited disease
  3. 3. cetirizine (daytime) ± hydroxyzine (night)
    rxcui 20610
    10 mg / 25 mg • PO • daily / nocte PRN
    trigger: Drug-eruption pruritus (Balakirski PMID 28412864)
    Symptomatic antihistamine adjunct; not disease-modifying

Auto-drafted A&P note

outpatient

Subjective

- Possible entry pathways: Symmetric, blanching, morbilliform/maculopapular eruption 4–14 d after a new drug — the common (~90%) benign exanthematous drug eruption (Wei/Nelson JAAD 2023 Part I PMID 37516359; Balakirski PMID 28412864); New high-risk culprit started in the SCAR window (β-lactam/sulfonamide 4–14 d morbilliform; allopurinol/aromatic anticonvulsant/sulfonamide/vancomycin 2–8 wk DRESS; aminopenicillin/macrolide <4 d AGEP) (Sassolas ALDEN PMID 20375998; Kardaun RegiSCAR PMID 23855313); Morbilliform eruption PLUS any SCAR red flag — mucosal involvement, facial edema, fever, skin pain/tenderness, blistering/Nikolsky, eosinophilia, organ derangement ("morbilliform that may be early SCAR") (Wei/Nelson JAAD 2023 Part II PMID 37516356).

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**Cutaneous drug eruption — morbilliform vs SCAR (dermatology lens)** (derm.drug-eruption.core.v1).
Phenotype framing: Terminal differential with named pivots: simple morbilliform/exanthematous (symmetric blanching, afebrile, no mucosa/organ — supportive) vs DRESS (facial edema + eosinophilia + 2–8 wk latency + organ — RegiSCAR pivot) vs SJS/TEN (mucositis + skin pain + detachment + Nikolsky pivot — route) vs AGEP (sterile non-follicular pustules + neutrophilia + rapid pivot) vs fixed drug eruption (recurrent same-site dusky round plaque pivot) vs urticarial/anaphylactic drug reaction (transient wheals + angio-oedema pivot — route) vs viral exanthem (no clear culprit, prodrome, pediatric — drug-timeline pivot) vs acute GVHD/Mycoplasma-induced rash-and-mucositis (pediatric, no drug-timeline pivot).
Scope: Frame the cutaneous drug-eruption SPECTRUM and the central triage question: benign simple morbilliform/exanthematous (~90%) vs life-threatening SCAR. STOP/identify the culprit drug is the universal cornerstone across every branch. SJS/TEN is recognised here and ROUTED to derm.sjs-ten.core.v1 (managed there, not re-authored). Anaphylactic/urticarial drug reactions route to allergy.anaphylaxis.v1 / derm.urticaria.core.v1.

No severity triggers fired against current inputs.

Plan

Regimen axis: **Cutaneous drug eruption — STOP-culprit-first + phenotype-stratified ladder (RegiSCAR / JAAD 2023 / ALDEN)** — step "Step 1 — STOP / identify the culprit drug (universal, every phenotype)".
1. discontinue probable culprit + all non-essential cross-reactors n/a (culprit_withdrawal, first line) — Sassolas ALDEN (PMID 20375998) + Wei/Nelson JAAD 2023 Part II (PMID 37516356) — identify the single most-probable culprit by latency window + ALDEN logic and stop it (plus cross-reactors); withdrawal is the universal cornerstone and, for SCAR, the dominant survival lever.
2. allergy-record + lifelong culprit/cross-reactor avoidance documentation n/a (decision_gate, first line) — Wei/Nelson JAAD 2023 Part II (PMID 37516356) — document the suspected culprit class + cross-reactors in the allergy record before disposition; never re-challenge a SCAR culprit (Sassolas ALDEN PMID 20375998).
3. defined-scenario treat-through decision gate (benign morbilliform only) (decision_gate, rescue) — Wei/Nelson JAAD 2023 Part I (PMID 37516359) — "treat-through" is acceptable ONLY for a mild isolated morbilliform eruption to an essential non-substitutable drug with NO SCAR features and close surveillance; any SCAR feature voids this gate.

Setting playbook (outpatient) — Identify and STOP the culprit, confirm a benign simple morbilliform eruption (no SCAR features), give supportive symptomatic care, and arm the patient with explicit SCAR return-precautions + an allergy-record entry (Wei/Nelson JAAD 2023 Part I PMID 37516359 + Part II PMID 37516356; Sassolas ALDEN PMID 20375998)
4. STOP probable culprit + non-essential cross-reactors n/a n/a immediate — Any drug-linked eruption (Sassolas ALDEN PMID 20375998) (Universal cornerstone; for SCAR the dominant survival lever)
5. triamcinolone 0.1% topical (symptomatic) 0.1% topical BID until settled — Pruritic benign morbilliform eruption (Balakirski PMID 28412864) (Symptomatic relief while culprit washes out; self-limited disease)
6. cetirizine (daytime) ± hydroxyzine (night) 10 mg / 25 mg PO daily / nocte PRN — Drug-eruption pruritus (Balakirski PMID 28412864) (Symptomatic antihistamine adjunct; not disease-modifying)

Non-pharmacologic actions:
- Written SCAR return-precautions: mucosal sores, facial swelling, fever, skin pain, blistering, malaise → return immediately (Wei/Nelson JAAD 2023 Part II PMID 37516356)
- Allergy-record entry: suspected culprit class + cross-reactors + safe alternatives before discharge (Sassolas ALDEN PMID 20375998)
- Scheduled 24–72 h re-check for delayed SCAR transition (Wei/Nelson JAAD 2023 Part II PMID 37516356)

AVOID / contraindication checks:
- Never re expose culprit or cross reacting class (Sassolas ALDEN PMID 20375998; Wei/Nelson JAAD 2023 Part II PMID 37516356 — re challenge of a SCAR culprit can be fatal)
- Dress requires long 6 12wk steroid taper rapid wean causes relapse (Kardaun RegiSCAR PMID 23855313; Wei/Nelson JAAD 2023 Part II PMID 37516356)
- Sjs ten spectrum not managed here route to derm.sjs ten.core.v1 (Parvathaneni Ocul Surf 2025 PMID 40541663 — recognise + route, do not re author)
- Cyclosporine avoid if severe renal impairment or active serious infection (Zita JMIR Dermatol 2023 PMID 37632913)
- Treat through only for mild isolated morbilliform no scar features essential drug (Wei/Nelson JAAD 2023 Part I PMID 37516359)
- Hla b 1502 screen before carbamazepine aromatic aeds and hla b 5801 before allopurinol (CPIC PMID 29392710; Hung PMID 15743917; McCormack HLA A 3101 PMID 21428769)
- Pregnancy cyclosporine acceptable weigh systemic steroid risk benefit (Wei/Nelson JAAD 2023 Part II PMID 37516356)

Monitoring

Regimen monitoring:
- benign morbilliform: clinical re-check 24-72h for SCAR transition (eosinophilia/organ can lag the rash) (Wei/Nelson JAAD 2023 Part II PMID 37516356)
- DRESS: serial CBC(eosinophils) + LFT + creatinine through the prolonged taper; relapse common on wean (Kardaun RegiSCAR PMID 23855313)
- DRESS: HHV-6/CMV reactivation + late autoimmune sequelae (thyroid, glucose) surveillance ≥1-2y (Wei/Nelson JAAD 2023 Part II PMID 37516356)
- AGEP: pustule resolution + post-pustular desquamation over days (Halevy PMID 19458527)
- cyclosporine: trough + renal function + BP during therapy (Zita JMIR Dermatol 2023 PMID 37632913)
- all: allergy-record + culprit/cross-reactor avoidance-card completion before disposition (Sassolas ALDEN PMID 20375998)

Setting (outpatient) monitoring:
- Re-check 24–72 h — emergence of fever/mucosa/facial edema/eosinophilia/organ = early SCAR (Wei/Nelson JAAD 2023 Part II PMID 37516356)
- Expect benign morbilliform to fade + desquamate over 1–2 wk after withdrawal (Wei/Nelson JAAD 2023 Part I PMID 37516359)

Follow-up plan: Lifelong culprit + cross-reactor avoidance card and allergy-record entry (highest-yield recurrence-prevention action). Pharmacogenomic counselling/HLA documentation where applicable (B*15:02/B*58:01/A*31:01). DRESS: structured long-term autoimmune-sequelae surveillance (thyroid, glucose) for ≥1–2 years and complete steroid taper. Patient/family education on never re-challenging the culprit class. Allergy/immunology referral for delabelling vs confirmed avoidance and for safe alternative selection.
- Close-out criterion: avoidance card + allergy record + (DRESS) sequelae-surveillance plan + pharmacogenomic counselling documented

Monitoring phase: Simple morbilliform: clinical re-check 24–72 h for SCAR-transition emergence (delayed eosinophilia/organ involvement can lag the rash). DRESS: serial CBC (eosinophils), LFT, creatinine through the taper; relapse common on steroid wean; HHV-6/CMV reactivation surveillance; watch for late autoimmune sequelae (thyroiditis, type-1 DM) months–years later. AGEP: pustule resolution + desquamation over days. Renal function via calc.ckd_epi_2021 where DRESS-AKI.

Disposition

Current setting: outpatient — Identify and STOP the culprit, confirm a benign simple morbilliform eruption (no SCAR features), give supportive symptomatic care, and arm the patient with explicit SCAR return-precautions + an allergy-record entry (Wei/Nelson JAAD 2023 Part I PMID 37516359 + Part II PMID 37516356; Sassolas ALDEN PMID 20375998)

Disposition criteria:
- Discharge with supportive plan + SCAR return-precautions if benign morbilliform, no SCAR features (Wei/Nelson JAAD 2023 Part I PMID 37516359)
- Admit / route OUT if any SCAR phenotype identified (Wei/Nelson JAAD 2023 Part II PMID 37516356)

Escalation triggers (move to higher acuity):
- Mucositis + skin pain + dusky/Nikolsky → route derm.sjs-ten.core.v1 (workup.sjs_ten) — SJS/TEN emergency (Parvathaneni PMID 40541663)
- Facial edema + eosinophilia + 2–8 wk latency + hepatitis/AKI → admit DRESS (workup.dress) (Kardaun RegiSCAR PMID 23855313)
- Urticaria + angio-oedema + airway/hypotension → route allergy.anaphylaxis.v1 (workup.anaphylaxis) (Balakirski PMID 28412864)

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Skin pain/tenderness, dusky/targetoid lesions, blisters, positive Nikolsky, or ≥2-site mucosal erosion on a drug-linked eruption (Parvathaneni Ocul Surf 2025 PMID 40541663)
- [LIFE_THREATENING] Facial/periorbital edema + eosinophilia (>1.5×10⁹/L) + 2–8 wk latency + lymphadenopathy + hepatitis/AKI on a morbilliform background — RegiSCAR probable/definite DRESS (Kardaun RegiSCAR PMID 23855313)
- [LIFE_THREATENING] Drug-linked transient wheals/angio-oedema with throat tightness, wheeze, or hypotension (Balakirski PMID 28412864)

Citations

- Wei/Nelson et al, JAAD 2023 DiHS/DRESS Part I (PMID 37516359) + Part II diagnosis & management (PMID 37516356) + Kardaun et al prospective RegiSCAR DRESS case definition/score (Br J Dermatol 2013, PMID 23855313) + Sassolas et al ALDEN drug-causality algorithm (Clin Pharmacol Ther 2010, PMID 20375998) + Parvathaneni et al SJS/TEN causality review (Ocul Surf 2025, PMID 40541663) + Halevy AGEP/EuroSCAR validation (Curr Opin Allergy Clin Immunol 2009, PMID 19458527) + CPIC HLA-B/HLA-A pharmacogenomic guideline (Clin Pharmacol Ther 2018, PMID 29392710) with Hung HLA-B*58:01 allopurinol (PNAS 2005, PMID 15743917) and McCormack HLA-A*31:01 carbamazepine (NEJM 2011, PMID 21428769); cyclosporine-in-DRESS evidence (Zita JMIR Dermatol 2023 PMID 37632913; Kirchhof JAMA Dermatol 2016 PMID 27438540); Balakirski cutaneous allergic drug-reaction review (Cutan Ocul Toxicol 2017, PMID 28412864) [PMID:37516359](https://pubmed.ncbi.nlm.nih.gov/37516359/)
- Cited evidence (PMID 37516356) [PMID:37516356](https://pubmed.ncbi.nlm.nih.gov/37516356/)
- Cited evidence (PMID 23855313) [PMID:23855313](https://pubmed.ncbi.nlm.nih.gov/23855313/)
- Cited evidence (PMID 20375998) [PMID:20375998](https://pubmed.ncbi.nlm.nih.gov/20375998/)
- Cited evidence (PMID 40541663) [PMID:40541663](https://pubmed.ncbi.nlm.nih.gov/40541663/)

Last reconciled with current guidelines: 2026-05-22.
References
  • Wei/Nelson et al, JAAD 2023 DiHS/DRESS Part I (PMID 37516359) + Part II diagnosis & management (PMID 37516356) + Kardaun et al prospective RegiSCAR DRESS case definition/score (Br J Dermatol 2013, PMID 23855313) + Sassolas et al ALDEN drug-causality algorithm (Clin Pharmacol Ther 2010, PMID 20375998) + Parvathaneni et al SJS/TEN causality review (Ocul Surf 2025, PMID 40541663) + Halevy AGEP/EuroSCAR validation (Curr Opin Allergy Clin Immunol 2009, PMID 19458527) + CPIC HLA-B/HLA-A pharmacogenomic guideline (Clin Pharmacol Ther 2018, PMID 29392710) with Hung HLA-B*58:01 allopurinol (PNAS 2005, PMID 15743917) and McCormack HLA-A*31:01 carbamazepine (NEJM 2011, PMID 21428769); cyclosporine-in-DRESS evidence (Zita JMIR Dermatol 2023 PMID 37632913; Kirchhof JAMA Dermatol 2016 PMID 27438540); Balakirski cutaneous allergic drug-reaction review (Cutan Ocul Toxicol 2017, PMID 28412864) — PMID:37516359
  • Cited evidence (PMID 37516356) — PMID:37516356
  • Cited evidence (PMID 23855313) — PMID:23855313
  • Cited evidence (PMID 20375998) — PMID:20375998
  • Cited evidence (PMID 40541663) — PMID:40541663