12-phase flow (12)

1. 1FRAME
   Frame as a CHRONIC immune-mediated (IL-23/Th17) systemic plaque disease managed treat-to-target (NPF: ≤1% BSA or PASI ≤1 at ~3 mo, reassess q6 mo) on a stepwise ladder — NOT a one-off rash. EVERY patient is screened for psoriatic arthritis + the cardiometabolic/MASLD/IBD/mood comorbidity cluster. The dermatologic emergencies (erythrodermic, generalized pustular) and the not-to-miss (CTCL/mycosis fungoides in resistant atypical disease) are recognised here.
   advance: chronic treat-to-target framing set; PsA + comorbidity + emergency + CTCL escape routes noted
2. 2ENTRY
   Recognise chronic sharply demarcated scaly plaque disease (extensor/scalp/gluteal-cleft) with the nail-pitting and chronic-relapsing entries vs the erythroderma/generalized-pustular emergency entry; capture plaque morphology + distribution up front.
   inputs: plaque_morphology_and_distribution
   actions: workup.chronic_pruritus
   advance: entry trigger present; plaque morphology + distribution recorded
3. 3CONTEXT
   Build the diagnosis + treatment context: psoriatic-arthritis screen (inflammatory joint/entheseal/back pain, dactylitis — at every visit), the cardiometabolic / metabolic-syndrome / MASLD / IBD / depression comorbidity inventory (psoriasis is a systemic disease, AAD-NPF 2019 comorbidities), trigger inventory (β-blocker, lithium, antimalarial, infection, stress, smoking, alcohol), and a rigorous prior-therapy-adequacy assessment (under-treatment is the commonest "failure").
   inputs: psoriatic_arthritis_screen, cardiometabolic_masld_ibd_mood_comorbidity, prior_topical_systemic_adequacy
   actions: workup.chronic_pruritus
   advance: clinical diagnosis supported; PsA screened; comorbidity + true-adequacy context established
4. 4RED_FLAGS
   Erythrodermic psoriasis (>90% BSA confluent erythema — thermoregulatory/fluid emergency, admission threshold). Generalized pustular psoriasis / von Zumbusch (widespread sterile pustules + fever + leukocytosis — emergency; spesolimab IL-36R for flares). Acute polyarticular psoriatic arthritis/dactylitis → urgent rheumatology to prevent irreversible joint damage. Serious active infection / untreated latent TB before any biologic.
   inputs: erythroderma_extent, generalized_pustulation_with_systemic_signs
   actions: panel.cbc, panel.inflammation
   advance: erythroderma / GPP / acute PsA / pre-biologic infection screened and escalated/routed if present
5. 5INITIAL_WORKUP
   Psoriasis 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 any biologic or methotrexate/cyclosporine) and (b) the differential (KOH/scraping for tinea, skin biopsy if CTCL/atypia or to separate from a confident mimic). Severity (PASI/BSA/PGA/DLQI) is scored clinically — not registry calculators — and captured narratively in RISK_STRATIFICATION.
   inputs: cbc_with_differential, lft, latent_tb_or_serious_infection
   actions: panel.cbc, panel.lft, panel.renal
   advance: differential tests sent as indicated; pre-systemic safety labs + latent-TB drawn if escalation likely
6. 6BRANCHING_WORKUP
   Papulosquamous-differential decision tree: sharp salmon plaque + silver scale + nail pits + extensor/scalp → psoriasis; ill-defined weeping flexural + atopy → atopic/nummular eczema (route derm.atopic-dermatitis.core.v1); KOH-positive annular advancing scale → tinea; greasy scale + scalp/nasolabial → seborrheic dermatitis; fixed poikilodermatous patches / treatment-resistant atypical adult → SKIN BIOPSY for mycosis fungoides/CTCL before chronic immunosuppression; cephalo-caudal salmon erythroderma + islands of sparing + keratoderma → pityriasis rubra pilaris; palmoplantar + mucosal + serology → secondary syphilis; new/worsening after β-blocker/lithium/antimalarial/TNF-paradoxical → drug-induced psoriasis (route derm.drug-eruption.core.v1); photodistributed annular/discoid + ANA → cutaneous lupus.
   inputs: drug_trigger_betablocker_lithium_antimalarial_tnf, adult_atypical_treatment_resistant_disease
   actions: workup.chronic_pruritus
   advance: psoriasis confirmed clinically OR an alternative papulosquamous diagnosis assigned + routed; CTCL excluded/biopsied in atypical resistant disease
7. 7DIFFERENTIAL
   Terminal papulosquamous differential with named pivots: plaque psoriasis (sharp salmon plaque + silvery scale + Auspitz + nail pits + extensor/scalp/gluteal-cleft pivot) vs atopic/nummular eczema (ill-defined, weeping, flexural, itch-dominant, atopy pivot — route derm.atopic-dermatitis.core.v1) vs tinea corporis (KOH+ annular advancing scale pivot) vs seborrheic dermatitis (greasy scale + scalp/nasolabial pivot) vs mycosis fungoides/CTCL (fixed poikilodermatous + biopsy pivot) vs pityriasis rubra pilaris (cephalo-caudal + islands of sparing + orange keratoderma pivot) vs secondary syphilis (palmoplantar + mucous patches + RPR/TPPA pivot) vs drug-induced/paradoxical psoriasis (β-blocker/lithium/antimalarial/TNF temporal link pivot — route derm.drug-eruption.core.v1) vs cutaneous lupus (photodistribution + ANA + interface biopsy pivot).
   advance: single best diagnosis selected; CTCL actively excluded in resistant atypical disease; drug trigger reconciled
8. 8RISK_STRATIFICATION
   Severity = BSA × PGA × special-site × QoL (PASI/BSA/PGA/DLQI scored clinically — schema-blocked as registry calculators, captured narratively). Mild (<3% BSA, no special site) → topical-only; moderate (3-10% BSA) → optimised topicals ± phototherapy ± step to systemic if special-site/QoL burden or PsA; severe (>10% BSA, or special-site/PsA/high QoL impact) → systemic (biologic or oral) first-line. Treat-to-target: NPF ≤1% BSA / PASI ≤1 at ~3 mo, reassess q6 mo. PsA presence upgrades to a PsA-active agent regardless of skin BSA.
   inputs: body_surface_area_involved, special_site_involvement
   advance: mild/moderate/severe tier + treat-to-target goal + escalation decision assigned
9. 9TREATMENT
   STEPWISE ladder. Step 1 topical (mild–moderate or adjunct any severity): high/mid-potency TCS + vitamin-D analog (calcipotriene), combination calcipotriene-betamethasone, tazarotene, TCI for face/folds, tapinarof, roflumilast cream, coal tar; proactive/weekend maintenance. Step 2 phototherapy: nbUVB (moderate, topical-refractory, systemic-deferred). Step 3 systemic non-biologic: methotrexate + folic acid / apremilast (PDE4) / acitretin (teratogenic — pregnancy-contraindicated) / cyclosporine (short-term bridge) / deucravacitinib (oral TYK2). Step 4 biologic by target: TNF-α (adalimumab/etanercept/infliximab/certolizumab pegol), IL-17 (secukinumab/ixekizumab/brodalumab/bimekizumab), IL-23 (guselkumab/risankizumab/tildrakizumab), IL-12/23 (ustekinumab). Comorbidity gating: IL-17 caution/avoid in active IBD (IL-23/TNF preferred); TNF/IL-17 require latent-TB screen; IL-23/IL-17 generally highest skin clearance; PsA present → TNF/IL-17/IL-23 (or oral) with joint activity. Pregnancy → certolizumab pegol preferred, acitretin/MTX absolutely avoided.
   inputs: pregnancy_lactation, age, creatinine
   advance: appropriate ladder step started; treat-to-target goal set; agent gated on PsA / comorbidity / pregnancy / infection / age
10. 10DISPOSITION
    Almost entirely outpatient/derm-clinic. Admission only for: erythrodermic psoriasis with thermoregulatory/fluid/haemodynamic compromise, generalized pustular psoriasis with systemic illness, or severe disease with serious superimposed infection. Systemic-therapy initiation/monitoring via dermatology; acute PsA → rheumatology; route emergencies/complications OUT by engine_id.
    inputs: erythroderma_extent, generalized_pustulation_with_systemic_signs
    advance: disposition documented; admission only for emergency criteria; derm follow-up + PsA/comorbidity referrals arranged
11. 11MONITORING
    Disease: BSA/PGA/PASI + QoL at ~3 mo to judge treat-to-target attainment (≤1% BSA / PASI ≤1), reassess q6 mo and at each step change (biologic effect by 12-16 wk). Drug safety: methotrexate → CBC/LFT periodically + folic acid co-prescribed; cyclosporine → BP + creatinine (via calc.ckd_epi_2021) ~q2wk during titration; acitretin → LFT/triglycerides; biologics → TB/infection surveillance, IL-17 candida/IBD-flare vigilance. Track under-treatment and adherence; cardiometabolic + mood surveillance ongoing.
    inputs: lipid_panel, creatinine
    actions: panel.cbc, panel.lft
    advance: treat-to-target reassessed at the agent-appropriate interval; drug-class safety labs on schedule
12. 12FOLLOWUP
    Chronic-disease maintenance: treat-to-target reassessment q6 mo, proactive topical maintenance to recurrence-prone sites, lifelong PsA surveillance (early referral prevents irreversible joint damage), cardiometabolic / metabolic-syndrome / MASLD / IBD / depression screening and risk-factor modification (smoking, alcohol, weight — AAD-NPF 2019 comorbidities), trigger counselling (avoid systemic-steroid pulse — rebound/pustular flare risk), and step-down/step-up criteria. Dermatology continuity for any systemic agent; reassess CTCL if course remains atypical.
    inputs: psoriatic_arthritis_screen, cardiometabolic_masld_ibd_mood_comorbidity
    actions: workup.chronic_pruritus
    advance: treat-to-target + proactive maintenance + PsA + comorbidity surveillance + trigger education documented