12-phase flow (12)

1. 1FRAME
   Frame as a CHRONIC RELAPSING Malassezia-associated inflammatory dermatosis of sebaceous-rich skin managed by site/severity/age — induction THEN intermittent maintenance, NOT a one-off rash. Dandruff = the mild scalp variant; infantile cradle cap = a self-limited variant managed conservatively. Severe/explosive/extensive/erythrodermic or treatment-resistant SD is a flag for HIV / immunosuppression / Parkinson-neurologic disease; recalcitrant petechial infantile "SD" = the Langerhans-cell-histiocytosis / Leiner not-to-miss — both recognised here as escape routes.
   advance: chronic relapsing SD framing set; dandruff + infantile variants + HIV/neuro + LCH/Leiner escape routes noted
2. 2ENTRY
   Recognise greasy-scale erythema in a seborrheic distribution (or fine dandruff flaking, or infantile cradle cap) vs the explosive/erythrodermic-SD underlying-disease entry; capture distribution + scale quality + age up front (age splits infantile vs adult arcs).
   inputs: lesion_distribution_and_scale_quality, age
   actions: workup.chronic_pruritus
   advance: entry trigger present; distribution/scale quality + age recorded
3. 3CONTEXT
   Build the diagnosis + treatment context: inflammatory flare vs pure scaling, the relapse pattern + true prior-topical adequacy (under-treatment / wrong vehicle / poor adherence is the commonest "failure"), and a rigorous HIV / immunosuppression / Parkinson-neurologic risk assessment (severe/explosive/extensive/resistant SD is a recognised marker of these). Counsel the relapsing nature + need for maintenance from the outset.
   inputs: inflammation_vs_pure_scaling, prior_topical_adequacy_and_relapse_pattern, hiv_immunosuppression_neurologic_risk
   actions: workup.chronic_pruritus
   advance: inflammatory-vs-scaling + relapse/adequacy + HIV/immunosuppression/neuro context established
4. 4RED_FLAGS
   Erythrodermic / extensive severe SD (>90% BSA — thermoregulatory/fluid risk AND a strong HIV/immunosuppression flag → urgent screen + systemic therapy). Explosive sudden-onset severe SD in an at-risk adult → HIV test. Infantile recalcitrant SD-like erythroderma with petechiae/purpura/erosions/failure-to-thrive/diarrhoea → exclude Langerhans-cell histiocytosis / Leiner's disease (biopsy + immunodeficiency workup — not-to-miss). Severe scalp SD with hair shedding / secondary bacterial infection.
   inputs: erythroderma_or_extensive_severe_extent, infantile_recalcitrant_petechial_failure_to_thrive
   actions: panel.cbc
   advance: erythroderma/explosive-SD/HIV-flag + infantile LCH-Leiner not-to-miss screened and escalated/routed if present
5. 5INITIAL_WORKUP
   SD is a CLINICAL diagnosis — no test confirms it. Targeted workup is for (a) the underlying-disease screen when SD is severe/explosive/extensive/erythrodermic or treatment-resistant (HIV test; immunosuppression review; Parkinson/neuro assessment; CBC) and (b) the differential — KOH/fungal exam for tinea, skin biopsy for the recalcitrant atypical adult or the petechial recalcitrant infant (LCH). Oral-antifungal pre-treatment LFT if the severe branch is likely.
   inputs: cbc_with_differential
   actions: panel.cbc, panel.lft
   advance: differential + underlying-disease tests sent as indicated; pre-oral-antifungal LFT drawn if escalation likely
6. 6BRANCHING_WORKUP
   Papulosquamous/facial-differential decision tree: greasy scale + seborrheic distribution + Malassezia-responsiveness → SD; sharper thicker silver-scaled plaques / scalp beyond hairline / nail pits / extensor disease → sebopsoriasis/psoriasis (route derm.psoriasis.core.v1); ill-defined itchy flexural eczema + atopy → atopic dermatitis (route derm.atopic-dermatitis.core.v1); centrofacial erythema/papulopustules with flushing + NO scale → rosacea (route derm.rosacea.core.v1); annular advancing scale + alopecia/broken hairs + KOH+ → tinea capitis/faciei (route derm.tinea-dermatophytosis.core.v1); geometric margin + exposure → contact dermatitis (route derm.contact-dermatitis.core.v1); photodistributed scarring scaly plaques → DLE/SCLE (biopsy + ANA/ENA serology); palmoplantar + mucosal + RPR → secondary syphilis; pityriasis amiantacea (thick asbestos-like adherent scalp scale binding hairs — a reaction pattern, search SD/psoriasis/tinea cause).
   inputs: sebopsoriasis_overlap_features, koh_indicated_features, hiv_test
   actions: workup.chronic_pruritus
   advance: SD confirmed clinically OR an alternative diagnosis assigned + routed; HIV offered in explosive/resistant adult; LCH biopsied in petechial recalcitrant infant
7. 7DIFFERENTIAL
   Terminal differential with named pivots: SD (greasy yellow scale + seborrheic distribution + Malassezia-responsive pivot) vs scalp/facial psoriasis & sebopsoriasis (sharper border + thicker silvery scale + nail pits + Auspitz + scalp beyond hairline pivot — route derm.psoriasis.core.v1) vs atopic dermatitis (ill-defined itchy flexural + atopy pivot — route derm.atopic-dermatitis.core.v1) vs rosacea (centrofacial flushing/papulopustules, NO scale pivot — route derm.rosacea.core.v1) vs tinea capitis/faciei (KOH+ annular advancing border + alopecia pivot — route derm.tinea-dermatophytosis.core.v1) vs contact dermatitis (geometric margin + exposure pivot — route derm.contact-dermatitis.core.v1) vs DLE/SCLE (photodistributed, scarring, follicular plugging + serology/biopsy pivot) vs Langerhans-cell histiocytosis (infantile recalcitrant petechial/erosive + biopsy pivot — not-to-miss) vs pityriasis amiantacea (asbestos-like hair-binding scale — reaction-pattern pivot) vs secondary syphilis (palmoplantar + mucous patches + RPR/TPPA pivot).
   advance: single best diagnosis selected; sebopsoriasis overlap flagged; HIV/immunosuppression actively considered in severe/resistant disease; LCH excluded in petechial recalcitrant infant
8. 8RISK_STRATIFICATION
   Severity = site × extent × inflammation × relapse-burden, age-stratified. Mild (dandruff / limited mild SD) → antifungal/keratolytic topical/shampoo only. Moderate (inflammatory facial/body/scalp SD) → topical antifungal + short topical corticosteroid/CNI or roflumilast foam, then maintenance. Severe / extensive / erythrodermic / recalcitrant → oral antifungal pulse PLUS an HIV / immunosuppression / neurologic investigation. Infant → conservative regardless of nuisance extent unless red-flag petechial/failure-to-thrive features (then LCH/Leiner pathway). Schema-blocked clinical severity scales (SDASI / IGA) captured narratively.
   inputs: body_site_and_extent
   advance: mild/moderate/severe tier + age branch + escalation/underlying-disease decision assigned
9. 9TREATMENT
   SITE/SEVERITY/AGE-stratified ladder + relapse-prevention maintenance. Scalp/dandruff: antifungal/keratolytic medicated shampoo (ketoconazole 2%, ciclopirox, selenium sulfide, zinc pyrithione, coal tar) ± short topical-corticosteroid solution for an inflammatory flare; salicylic-acid for thick adherent scale. Face/body: topical antifungal (ketoconazole/ciclopirox cream), topical calcineurin inhibitor (steroid-sparing for face + maintenance), low-potency topical corticosteroid SHORT course for flare, topical roflumilast 0.3% foam (non-steroidal, FDA-approved for SD). Severe/extensive/recalcitrant: oral antifungal pulse (itraconazole/fluconazole) + investigate underlying HIV/immunosuppression/neuro. Infantile cradle cap: emollient/oil + soft brushing + gentle non-medicated or low-strength antifungal shampoo; usually self-limited (reassure) — avoid potent agents. ALL: intermittent maintenance prophylaxis (relapsing disease — counsel). Gating: prolonged facial potent steroid AGAINST (atrophy/steroid-rosacea — prefer CNI/antifungal/roflumilast); oral azole hepatotoxicity + CYP3A4 DDI; infant — avoid potent steroids/oral antifungals; pregnancy — topical-first, avoid oral azoles.
   inputs: pregnancy_lactation, facial_corticosteroid_exposure, concomitant_medications_cyp3a4, lft
   advance: site/severity/age-appropriate step started; maintenance-prophylaxis plan defined; agent gated on facial-steroid/pregnancy/infant/DDI status
10. 10DISPOSITION
    Almost entirely outpatient. No admission for ordinary SD. The exceptions route OUT, not in: erythrodermic/extensive severe SD → urgent HIV/immunosuppression screen + dermatology (admission only if thermoregulatory/fluid compromise); explosive adult SD → HIV testing pathway; recalcitrant petechial/failure-to-thrive infant → urgent paediatric dermatology/heme-onc for LCH/Leiner workup. Routine SD → primary-care/derm continuity with a written induction + maintenance plan.
    inputs: erythroderma_or_extensive_severe_extent
    advance: disposition documented; underlying-disease/LCH referrals arranged for red-flag presentations; maintenance plan + follow-up set for routine SD
11. 11MONITORING
    Disease: reassess response at 2–4 weeks (most topical SD responds in 2–4 wk); if no response, re-examine the diagnosis (KOH, biopsy) and re-screen for underlying HIV/immunosuppression/neurologic disease. Drug safety: oral azole antifungal → baseline + on-treatment LFT (panel.lft) and CYP3A4 DDI surveillance; facial corticosteroid → atrophy/telangiectasia/perioral-dermatitis/rebound vigilance and early step-down to a steroid-sparing agent. Counsel that relapse is expected and reinforce maintenance adherence.
    inputs: lft
    actions: panel.lft
    advance: response reassessed at 2–4 wk; oral-antifungal LFT on schedule; dx/underlying-disease re-evaluated if treatment-resistant
12. 12FOLLOWUP
    Chronic relapsing-disease maintenance: intermittent prophylactic antifungal shampoo/topical to recurrence-prone sites (the core of relapse control — counsel explicitly), facial steroid-sparing maintenance (CNI / antifungal / roflumilast), trigger counselling (stress, cold/dry season, infrequent washing), and education that SD is controllable but not curable. For the infant: reassure (self-limited, typically resolves by ~8–12 months) with return precautions for petechial/erosive/failure-to-thrive change. Re-evaluate for HIV/neurologic disease at follow-up if the course remains atypically severe or treatment-resistant.
    inputs: prior_topical_adequacy_and_relapse_pattern
    actions: workup.chronic_pruritus
    advance: maintenance-prophylaxis + trigger counselling + relapse education documented; infant reassured with return precautions; underlying-disease re-screen if course atypical