12-phase flow (12)

1. 1FRAME
   Frame as a CHRONIC relapsing type-2 barrier disease managed on a barrier-first + stepwise anti-inflammatory ladder, NOT a one-off rash. Acute complications (eczema herpeticum, impetiginised eczema, erythroderma) are recognised here and routed/escalated. The not-to-miss is adult treatment-resistant "eczema" = CTCL until biopsy says otherwise.
   advance: chronic AD framing set; complication + CTCL escape routes noted
2. 2ENTRY
   Recognise chronic/relapsing intensely pruritic eczematous disease with atopic diathesis vs the acute eczema-herpeticum / topical-refractory entries; capture itch severity up front (the primary PRO driving escalation).
   inputs: pruritus_severity
   actions: workup.chronic_pruritus
   advance: entry trigger present; itch severity recorded
3. 3CONTEXT
   Build the diagnosis + treatment context: age-typical distribution/morphology, atopic comorbidities (asthma/AR/food allergy/EoE — the atopic march and shared IL-4/13 axis), trigger inventory (irritants, aeroallergens, sweat, S. aureus, stress), and a rigorous prior-topical-adequacy assessment (potency × quantity × duration × adherence — under-treatment is the commonest "failure").
   inputs: lesion_distribution_morphology, atopic_comorbidities, prior_topical_adequacy
   actions: workup.chronic_pruritus
   advance: clinical diagnosis supported; trigger + true-adequacy context established
4. 4RED_FLAGS
   Eczema herpeticum (acute monomorphic punched-out vesicles/erosions, fever, pain, malaise on eczematous skin) → urgent systemic aciclovir + ophthalmology if periocular, route to ID/derm-emergency. Impetiginised eczema (honey-crust, pustules, weeping) → anti-staphylococcal therapy. Erythrodermic flare (>90% BSA) → thermoregulatory/fluid risk + admission threshold + Sézary consideration. Eczema herpeticum is the dermatologic emergency of AD.
   inputs: secondary_infection_signs, erythroderma_extent
   actions: panel.cbc, panel.inflammation
   advance: eczema-herpeticum / impetiginisation / erythroderma screened and escalated/routed if present
5. 5INITIAL_WORKUP
   AD is a clinical diagnosis — no test confirms it. Targeted workup is for (a) systemic-ladder readiness (CBC, LFT, creatinine, lipids, latent-TB + HBV/HCV before JAK/immunosuppressant) and (b) the differential (KOH/scraping for tinea/scabies, patch testing if superimposed ACD suspected, skin biopsy if CTCL/atypia). Total-IgE/allergy testing is NOT required to diagnose AD (AAD 2023).
   inputs: cbc_with_differential, lft, infection_screen_tb_hbv_hcv
   actions: panel.cbc, panel.lft, panel.renal
   advance: differential tests sent as indicated; pre-systemic safety labs drawn if escalation likely
6. 6BRANCHING_WORKUP
   Eczematous-differential decision tree: KOH-negative + flexural + atopy → AD; geometric/linear margin + exposure → allergic/irritant contact dermatitis (route derm.contact-dermatitis.core.v1, patch test); burrows + web-space/genital + household itch → scabies (route derm.scabies.core.v1); well-demarcated salmon plaques + silvery scale + nail pits → psoriasis (route derm.psoriasis.core.v1); adult-onset, fixed, poikilodermatous, treatment-resistant, atypical → SKIN BIOPSY for mycosis fungoides/CTCL before chronic immunosuppression. Concomitant ACD frequently coexists with AD — low patch-test threshold in recalcitrant disease.
   inputs: adult_new_onset_treatment_resistant
   actions: workup.chronic_pruritus
   advance: AD confirmed clinically OR an alternative dermatosis assigned + routed; CTCL excluded/biopsied in atypical adult disease
7. 7DIFFERENTIAL
   Terminal eczematous differential with named pivots: AD vs allergic contact dermatitis (geometric margin + patch-test pivot) vs irritant contact dermatitis (exposure + burning>itch pivot) vs seborrheic dermatitis (greasy scale + scalp/nasolabial pivot) vs psoriasis (sharp salmon plaque + silver scale + Auspitz pivot) vs scabies (burrow + web-space + contact itch pivot) vs nummular eczema (coin lesions pivot) vs tinea corporis (KOH+ annular advancing scale pivot) vs CTCL/mycosis fungoides (fixed poikilodermatous patches + biopsy pivot) vs drug eruption (temporal drug link pivot — route derm.drug-eruption.core.v1).
   advance: single best diagnosis selected; coexisting ACD flagged; CTCL actively excluded in resistant adult disease
8. 8RISK_STRATIFICATION
   Severity = BSA × intensity × itch × QoL/sleep (EASI/SCORAD/POEM/IGA where available — schema-blocked as TS calculators, captured narratively). Mild → topical-only; moderate → optimised topicals ± phototherapy ± step to systemic if refractory/QoL burden; severe / topical-refractory / high QoL impact → systemic (biologic or oral JAK) first-line. Type-2 comorbidity burden (asthma/EoE) and itch dominance steer agent choice.
   inputs: body_surface_area_involved, pruritus_severity
   advance: mild/moderate/severe tier + escalation decision assigned
9. 9TREATMENT
   BARRIER-FIRST always (emollient ≥250 g/wk, bathing + immediate emollient, trigger mitigation) + the stepwise anti-inflammatory ladder. Acute flare: short higher-potency TCS burst → step down; maintenance: PROACTIVE twice-weekly TCS/TCI to recurrence-prone sites (halves relapse). TCI / topical-PDE4 / topical-JAK / tapinarof / roflumilast are steroid-sparing for face/folds/long-term. Topical failure (adequate trial) → phototherapy or systemic: first-line biologic (dupilumab / tralokinumab / lebrikizumab / nemolizumab+TCS) or oral JAK (upadacitinib / abrocitinib / baricitinib); cyclosporine as a rapid short bridge; methotrexate / azathioprine / MMF conditional. Chronic systemic corticosteroids are recommended AGAINST (rebound, harm). Comorbidity gating: pregnancy → avoid JAK/MTX/MMF (dupilumab preferred); thrombotic/age≥65 → prefer biologic over JAK; concomitant asthma/EoE → dupilumab dual-indication.
   inputs: pregnancy_lactation, age, thrombotic_cardiovascular_risk, creatinine
   advance: barrier plan + appropriate ladder step started; proactive maintenance defined; agent gated on comorbidity/pregnancy/age
10. 10DISPOSITION
    Almost entirely outpatient/derm-clinic. Admission only for: eczema herpeticum with systemic illness/periocular involvement, severe erythrodermic flare with thermoregulatory/fluid compromise, or severe superinfection failing oral therapy. Systemic-therapy initiation/monitoring via dermatology; route complications OUT by engine.
    inputs: erythroderma_extent, secondary_infection_signs
    advance: disposition documented; admission only for complication criteria; derm follow-up arranged
11. 11MONITORING
    Disease: itch NRS + BSA/IGA + QoL/sleep at 4-16 wk to judge step response (biologic effect by 12-16 wk; oral JAK faster, days-weeks). Drug safety: JAK → CBC, LFT, lipids at ~4-12 wk then periodic, VTE/MACE/zoster vigilance; cyclosporine → BP + creatinine q2wk during titration; methotrexate → CBC/LFT; biologics → conjunctivitis (dupilumab), injection-site, rare facial erythema. Watch tachyphylaxis/under-dosing and proactive-maintenance adherence.
    inputs: lipid_panel, creatinine
    actions: panel.cbc, panel.lft
    advance: objective response assessed at the agent-appropriate interval; drug-class safety labs on schedule
12. 12FOLLOWUP
    Chronic-disease maintenance: lifelong emollient/barrier habit + written eczema action plan (green/yellow/red flare steps), proactive twice-weekly anti-inflammatory to recurrence-prone sites, trigger control, atopic-march + mental-health + sleep + comorbidity surveillance (AAD 2022), education on quantity (fingertip unit) and TCS-phobia counselling, and step-down/step-up criteria. Dermatology continuity for any systemic agent; reassess CTCL if course remains atypical.
    inputs: atopic_comorbidities, prior_topical_adequacy
    actions: workup.chronic_pruritus
    advance: action plan + proactive maintenance + comorbidity surveillance + education documented