12-phase flow (12)

1. 1FRAME
   Frame as a CHRONIC T-cell-mediated lichenoid mucocutaneous disease whose management is VARIANT-STRATIFIED: classic cutaneous is often self-limited (symptom control) whereas oral/genital erosive is premalignant (surveillance) and lichen planopilaris/FFA + nail are scarring (irreversible — treat early). Lichenoid drug eruption is the key mimic recognised here and routed by engine_id. HCV has a reciprocal association and is screened.
   advance: variant-stratified framing set; premalignant + scarring + lichenoid-drug-eruption + HCV escape routes noted
2. 2ENTRY
   Recognise the LP variant at presentation: classic pruritic violaceous polygonal papules with Wickham striae vs reticular/erosive oral vs erosive genital/vulvovaginal-gingival vs scarring alopecia/nail vs the new-drug-then-lichenoid-eruption entry; capture variant + pruritus/pain severity up front.
   inputs: lesion_morphology_and_variant, pruritus_and_pain_severity
   actions: workup.chronic_pruritus
   advance: entry trigger present; variant + symptom severity recorded
3. 3CONTEXT
   Build the diagnosis + treatment context: Wickham striae / dermoscopy confirmation, tobacco + alcohol use (independent OLP malignant-transformation risk factors), HCV risk/status (reciprocal LP–HCV association), age/polypharmacy (lichenoid-drug-eruption prior), and a rigorous prior-therapy adequacy assessment (under-treatment is the commonest "failure", especially for oral topicals).
   inputs: wickham_striae_dermoscopy, tobacco_alcohol_use, hcv_risk_or_status, age
   actions: workup.chronic_pruritus
   advance: clinical diagnosis supported; tobacco/alcohol + HCV + drug-timeline context established
4. 4RED_FLAGS
   Oral/genital erosive LP with a NON-HEALING, indurated, ulcerated, or leukoplakic area → urgent biopsy for squamous cell carcinoma (premalignant disease). Rapidly progressive lichen planopilaris/FFA or nail pterygium → IRREVERSIBLE scarring, escalate aggressively to halt activity. Severe erosive disease impairing oral intake / function. Lichenoid drug eruption suspected → reconcile + withdraw culprit (route derm.drug-eruption.core.v1). HCV-positive → hepatology.
   inputs: non_healing_indurated_oral_lesion, scarring_variant_activity
   actions: panel.cbc, panel.lft
   advance: SCC-suspect lesion / scarring-variant activity / functional impairment / lichenoid-drug / HCV screened and escalated or routed if present
5. 5INITIAL_WORKUP
   LP is a clinico-pathologic diagnosis. Targeted workup: skin/mucosal biopsy (band-like subepidermal lymphocytic infiltrate, sawtooth rete, Civatte bodies) + DIF for the oral/genital erosive differential (separate from pemphigus/MMP/discoid lupus); anti-HCV serology (reciprocal association); pre-systemic safety labs (CBC, LFT, creatinine) when a systemic step is likely. Biopsy any non-healing/indurated oral lesion for SCC.
   inputs: hcv_serology, cbc_with_differential, lft
   actions: panel.cbc, panel.lft, panel.renal
   advance: biopsy ± DIF sent as indicated; HCV serology + pre-systemic safety labs drawn if escalation likely
6. 6BRANCHING_WORKUP
   Lichenoid-differential decision tree: classic Wickham-striae papules + biopsy interface dermatitis → LP; new/changed drug + photodistribution + later onset → lichenoid drug eruption (route derm.drug-eruption.core.v1); sharp salmon plaque + silver scale + nail pits → psoriasis (route derm.psoriasis.core.v1); ill-defined itchy flexural + atopy → atopic/lichen-simplex (route derm.atopic-dermatitis.core.v1); photodistributed annular/discoid scalp/oral + ANA + interface biopsy with deep infiltrate / DIF lupus band → discoid/cutaneous lupus (route rheum.sle.core.v1); oral erosive with DIF intercellular/linear-BMZ → pemphigus/mucous-membrane pemphigoid (biopsy + DIF); genital white atrophic plaques → lichen sclerosus; lichenoid GVHD in a transplant host; palmoplantar/mucosal + serology → secondary syphilis.
   inputs: medication_timeline_for_lichenoid_eruption
   actions: workup.chronic_pruritus
   advance: LP confirmed clinico-pathologically OR an alternative lichenoid/erosive diagnosis assigned + routed; lichenoid drug eruption excluded/withdrawn
7. 7DIFFERENTIAL
   Terminal lichenoid differential with named pivots: lichen planus (Wickham striae + violaceous polygonal papules + band-like lymphocytic interface biopsy pivot) vs lichenoid drug eruption (drug timeline + photodistribution + eosinophils/parakeratosis on biopsy pivot — route derm.drug-eruption.core.v1) vs psoriasis (sharp salmon plaque + silver scale + Auspitz + nail pits pivot — route derm.psoriasis.core.v1) vs discoid/cutaneous lupus (photodistribution + ANA + DIF lupus band + follicular plugging pivot — route rheum.sle.core.v1) vs lichen simplex chronicus (lichenified solitary pruritus plaque pivot) vs lichenoid GVHD (allogeneic-transplant context pivot) vs secondary syphilis (palmoplantar + mucous patches + RPR/TPPA pivot) vs oral leukoplakia / candidiasis / pemphigus / mucous-membrane pemphigoid (oral erosive — biopsy + DIF pivot) vs lichen sclerosus (genital white atrophic plaque pivot) vs pityriasis rosea (herald patch + Christmas-tree pivot).
   advance: single best diagnosis selected; lichenoid drug eruption actively excluded; erosive-oral DIF differential resolved
8. 8RISK_STRATIFICATION
   Stratify by VARIANT + severity (no validated registry calculator — ODSS/OHIP/LPPAI captured narratively). Classic cutaneous limited → topical-only (often self-limited). Extensive/refractory cutaneous → systemic/phototherapy. Oral/genital ATROPHIC-EROSIVE (red) subtype → highest malignant-transformation risk (erosive RR 4.09; tongue RR 1.82) → topical/systemic + lifelong surveillance. Lichen planopilaris/FFA + nail pterygium → SCARRING — irreversible, upgrade urgency independent of extent. HCV+ / smoker / drinker upgrades surveillance intensity.
   inputs: erosive_atrophic_change_at_mucosa
   actions: calc.ckd_epi_2021
   advance: variant + severity tier + surveillance intensity + scarring-urgency + escalation decision assigned
9. 9TREATMENT
   VARIANT-STRATIFIED ladder. Cutaneous limited: high-potency topical corticosteroid (clobetasol) / topical calcineurin (tacrolimus) / intralesional triamcinolone (hypertrophic) + antihistamine for itch. Extensive/refractory cutaneous: oral corticosteroid short course → acitretin (first-line systemic, Cribier) / phototherapy (nbUVB/PUVA) / methotrexate / mycophenolate / metronidazole / sulfasalazine (selected). Oral erosive: topical corticosteroid gel/rinse (clobetasol/dexamethasone/fluocinonide; Cochrane RR 1.91) → topical tacrolimus → intralesional/systemic steroid → acitretin (+TAC ODSS-75 88% vs 47%) for refractory; + candidiasis prophylaxis (nystatin) + analgesia + SCC surveillance. Genital/erosive vulvovaginal: ultrapotent topical steroid + maintenance + dilator/specialist. Lichen planopilaris/FFA (scarring — urgency): topical/intralesional steroid + hydroxychloroquine ± oral retinoid/doxycycline/PPARγ; 5α-reductase inhibitor (finasteride/dutasteride) for FFA. Non-pharm: HCV referral, withdraw lichenoid-culprit drug, tobacco/alcohol cessation, dental/irritant control. Gate on pregnancy (avoid retinoid/MTX/MMF) + HCQ retinopathy screen + steroid taper.
   inputs: pregnancy_lactation, creatinine, hydroxychloroquine_retinopathy_risk
   advance: variant-appropriate ladder step started; surveillance + non-pharm anchors set; agent gated on pregnancy / HCQ-screen / steroid-taper
10. 10DISPOSITION
    Entirely outpatient/derm-clinic. No admission pathway — escalate via specialty referral: oral medicine/OMFS + biopsy for SCC-suspect oral lesions, hepatology for HCV+, gynaecology/urology for erosive genital disease with scarring, multidisciplinary scarring-alopecia clinic for progressive LPP/FFA. Lichenoid drug eruption → route derm.drug-eruption.core.v1 and reconcile the culprit. Systemic-agent initiation/monitoring via dermatology.
    inputs: non_healing_indurated_oral_lesion
    advance: disposition documented; outpatient continuity + variant-specific referrals arranged; SCC-suspect lesion expedited
11. 11MONITORING
    Disease: cutaneous lesion/itch at 4–12 wk; oral erosive ODSS/pain at 4–12 wk per step; scarring-variant (LPP/FFA) activity index + hairline/photography q3–6 mo (irreversible — judge halt of progression, not regrowth). SURVEILLANCE: oral/genital erosive LP periodic mucosal exam with biopsy of any change for SCC (lifelong; transformation ~1% overall, ~0.2–0.5%/yr, higher with erosive/tongue/HCV/tobacco). Drug safety: hydroxychloroquine baseline + periodic ophthalmology; acitretin LFT/triglycerides + pregnancy avoidance; methotrexate CBC/LFT + folic acid; systemic-steroid taper + glucose/BP/bone. Reassess for lichenoid-drug-eruption if course atypical.
    inputs: cbc_with_differential, lft, creatinine
    actions: panel.cbc, panel.lft, panel.renal
    advance: variant-appropriate response/surveillance reassessed; drug-class safety on schedule; SCC surveillance documented for erosive disease
12. 12FOLLOWUP
    Chronic-disease maintenance: lifelong oral/genital erosive-LP malignant-transformation surveillance with tobacco/alcohol-cessation counselling and dental/irritant control, scarring-variant (LPP/FFA/nail) early-treatment + activity surveillance to prevent irreversible loss, HCV-status follow-through with hepatology, drug-reconciliation review for any recurrent lichenoid eruption (elderly polypharmacy), proactive topical maintenance for relapse-prone erosive sites, and step-down/step-up criteria. Dermatology continuity for any systemic agent; reassess the lichenoid differential if the course remains atypical.
    inputs: tobacco_alcohol_use, hcv_risk_or_status
    actions: workup.chronic_pruritus
    advance: surveillance + cessation + scarring-early-treatment + HCV follow-through + drug-reconciliation + education documented