12-phase flow (12)

1. 1FRAME
   Frame as a SITE-DEFINED superficial dermatophyte infection where body site selects both the confirmatory test and the treatment-ladder step. Tinea capitis is ALWAYS systemic. Diagnosis is confirmed mycologically, never assumed — especially before any oral course. The two trap states framed here: tinea incognito (steroid-modified, the commonest mimic trap) and terbinafine-resistant T. indotineae (the emerging-resistance trap).
   advance: site-framed scope set; confirm-before-oral + incognito + T. indotineae traps noted
2. 2ENTRY
   Recognise the site-specific presentation (annular glabrous plaque / interdigital-moccasin foot / scaly scalp + broken hairs / dystrophic nail) vs the steroid-modified-or-resistant atypical entry; capture body site up front because it drives everything downstream.
   inputs: body_site_of_lesions
   actions: workup.chronic_pruritus
   advance: entry trigger present; body site recorded
3. 3CONTEXT
   Build the context that bends the prior and the ladder: lesion morphology/border/scale (advancing border + central clearing vs steroid-flattened incognito), prior corticosteroid exposure (incognito), prior antifungal + travel + treatment-failure (T. indotineae), immunocompromise (extensive/Majocchi), diabetes/PVD (tinea pedis as the cellulitis portal — route derm.cellulitis.core.v1).
   inputs: lesion_morphology_border_scale, prior_topical_or_systemic_corticosteroid, prior_antifungal_use_or_treatment_failure, immunocompromise, diabetes_or_peripheral_vascular_disease
   actions: workup.chronic_pruritus
   advance: morphology + steroid-exposure + resistance-risk + portal context established
4. 4RED_FLAGS
   Tinea capitis KERION (boggy, tender, inflammatory scalp mass ± lymphadenopathy) → systemic antifungal urgently (± short adjunctive steroid for inflammation) to limit scarring alopecia. Tinea incognito recognised here = STOP the corticosteroid and confirm mycologically before any further treatment. Suspected T. indotineae outbreak / extensive treatment-resistant disease → culture + susceptibility + stewardship. Tinea pedis as a cellulitis portal in diabetes → route derm.cellulitis.core.v1.
   inputs: extent_and_follicular_involvement, prior_topical_or_systemic_corticosteroid
   actions: panel.cbc
   advance: kerion / incognito / resistance / portal red flags screened and escalated/routed if present
5. 5INITIAL_WORKUP
   CONFIRM BEFORE TREATING — KOH microscopy is first-line, rapid, ~90% sensitive in nail series. Fungal culture or dermatophyte PCR (PCR sens ~93% vs culture; turnaround hours) for nail, scalp (species: Trichophyton vs Microsporum changes the capitis drug), and any resistance-suspect case. PAS/nail-plate histology when KOH-negative but clinically compelling. Baseline LFT/CBC if a prolonged oral course is anticipated. Onychomycosis and tinea capitis must be lab-confirmed before committing to months of oral therapy.
   inputs: koh_microscopy, fungal_culture_or_dermatophyte_pcr, lft, cbc_with_differential
   actions: panel.cbc, panel.lft, panel.renal
   advance: mycologic confirmation obtained (KOH ± culture/PCR ± PAS); species sought for scalp/nail/resistance; pre-oral safety labs drawn if needed
6. 6BRANCHING_WORKUP
   Site-and-mimic decision tree. Glabrous: KOH+ advancing annular scale → tinea corporis/cruris vs nummular eczema/AD (route derm.atopic-dermatitis.core.v1 if KOH−, no advancing border) vs psoriasis (route derm.psoriasis.core.v1) vs pityriasis rosea / granuloma annulare (no scale, KOH−) / erythema migrans / candidal intertrigo / seborrheic dermatitis. Scalp: tinea capitis vs alopecia areata (no scale, exclamation hairs) / seborrheic / psoriasis. Nail: onychomycosis vs psoriatic nail (pitting, oil-drop — route derm.psoriasis.core.v1) / lichen planus (dorsal pterygium) / trauma. Steroid-modified or KOH−-but-compelling → repeat sampling off steroid, culture/PCR; resistance-suspect → susceptibility testing / molecular ID for T. indotineae.
   inputs: prior_antifungal_use_or_treatment_failure
   actions: workup.chronic_pruritus
   advance: dermatophytosis confirmed by site OR a mimic assigned + routed by engine_id; resistance-suspect cases flagged for susceptibility/molecular ID
7. 7DIFFERENTIAL
   Terminal differential with named pivots: tinea corporis vs nummular eczema/AD (KOH+ + advancing scaly annular border with central clearing pivot; route derm.atopic-dermatitis.core.v1) vs psoriasis (sharp salmon plaque + silver scale + nail pits pivot; route derm.psoriasis.core.v1) vs pityriasis rosea (herald patch + collarette + Christmas-tree, KOH− pivot) vs granuloma annulare (no scale, dermal, KOH− pivot) vs erythema migrans (expanding non-scaly, tick exposure pivot) vs candidal intertrigo (satellite pustules, moist, KOH yeast/pseudohyphae pivot) vs seborrheic dermatitis (greasy scale, central-face/scalp pivot); tinea capitis vs alopecia areata (smooth, exclamation hairs, KOH− pivot) / seborrheic / psoriasis; onychomycosis vs psoriatic nail (pitting + oil-drop + skin psoriasis pivot) vs lichen planus (pterygium + longitudinal ridging pivot) vs traumatic dystrophy (single great-toe, history pivot). Steroid-response-worsens favours occult tinea (incognito).
   advance: single best site-specific diagnosis selected; incognito actively excluded if steroid history; mimic routed if assigned
8. 8RISK_STRATIFICATION
   Stratify by what mandates oral vs topical: localized glabrous limited BSA, immunocompetent, no follicular/nail/scalp involvement → topical adequate (Step 1). Extensive, follicular/Majocchi, immunocompromised, tinea incognito, any scalp (Step 3 always systemic), any nail (Step 4) → oral. Resistance modifiers: prior antifungal failure + extensive + travel → treat as possible terbinafine-resistant T. indotineae and adjust the ladder.
   inputs: extent_and_follicular_involvement, body_site_of_lesions
   advance: topical-adequate vs oral-required tier assigned; resistance modifier applied
9. 9TREATMENT
   SITE-STEPWISE ladder. Step 1 localized glabrous (corporis/cruris/pedis): topical allylamine (terbinafine — highest cure, Cochrane RR 4.51 vs placebo) or azole (clotrimazole/ketoconazole/miconazole) / naftifine / ciclopirox; duration by site (2 wk corporis/cruris, up to 4 wk + interdigital pedis, longer moccasin). Step 2 extensive/follicular/Majocchi/incognito/immunocompromised: oral terbinafine or itraconazole/fluconazole; in tinea incognito STOP the corticosteroid first. Step 3 tinea capitis ALWAYS systemic — oral terbinafine for Trichophyton (better for T. tonsurans, RR 1.47), griseofulvin for Microsporum (better for M. canis, RR 0.68), weight-based pediatric dosing + sporicidal selenium-sulfide/ketoconazole shampoo + treat household/fomites. Step 4 onychomycosis (confirm first): oral terbinafine continuous/pulse (~70-79% mycologic cure) or itraconazole pulse (~80-88%) or fluconazole; topical efinaconazole/tavaborole/ciclopirox for limited disease; eradicate the tinea-pedis reservoir; counsel slow nail outgrowth. Emerging-resistance branch: suspected/confirmed T. indotineae or terbinafine failure → higher-dose longer-course itraconazole, culture + susceptibility, stewardship. Gate on pregnancy (topical only), hepatic disease, CYP3A4 DDIs, age (weight-based peds), renal (fluconazole).
   inputs: age, pregnancy_lactation, hepatic_disease, cyp3a4_interacting_comedications, creatinine
   advance: site-appropriate ladder step started; oral course confirmed mycologically; agent gated on pregnancy/hepatic/DDI/age/renal; resistance branch applied if indicated
10. 10DISPOSITION
    Entirely outpatient/derm-clinic. No admission pathway: kerion, tinea incognito, and T. indotineae are managed in clinic with systemic therapy + dermatology continuity. Public-health notification/awareness for confirmed T. indotineae; treat household contacts and fomites for tinea capitis. Route the cellulitis-portal diabetic and the psoriatic/eczematous mimics OUT by engine_id.
    inputs: body_site_of_lesions
    advance: outpatient disposition documented; contacts/fomites + stewardship/notification addressed; mimics routed
11. 11MONITORING
    Disease: clinical + mycologic cure (repeat KOH/culture) at end of course — onychomycosis cure lags clinical outgrowth by months (slow nail growth is EXPECTED, not early failure; toenail clear-out ~9-12 mo). Tinea capitis: clinical + mycologic clearance at ~4-8 wk, treat to mycologic cure. Drug safety: LFT for prolonged oral terbinafine/azole/griseofulvin per duration/symptoms; itraconazole CYP3A4 DDIs ongoing. Non-response or relapse → reconfirm diagnosis, reassess adherence/reservoir, and consider terbinafine-resistant T. indotineae with susceptibility testing.
    inputs: lft
    actions: panel.lft
    advance: clinical + mycologic response assessed at the site-appropriate interval; nail-outgrowth expectation set; resistance reconsidered if failing
12. 12FOLLOWUP
    Recurrence prevention + reservoir control: footwear/hosiery hygiene, antifungal foot powder, treat tinea pedis as the onychomycosis + cellulitis reservoir, household/fomite treatment and screening for tinea capitis (combs, hats, pets for M. canis), athlete/communal-shower precautions, occupational counselling. Onychomycosis relapse-prevention with intermittent topical maintenance and pedis eradication. Confirmed T. indotineae → antifungal stewardship counselling (no empiric terbinafine monotherapy, avoid OTC combination steroid-antifungal creams that breed incognito) and dermatology continuity.
    inputs: diabetes_or_peripheral_vascular_disease, prior_antifungal_use_or_treatment_failure
    actions: workup.chronic_pruritus
    advance: reservoir + fomite + recurrence-prevention plan documented; stewardship counselling given; derm continuity arranged