Eduovisual
Skin & Subcutaneous Tissue
Lice and scabies: diagnosis and treatment
— Pediculus humanus capitis (head lice): scalp, school-aged children 3–11 yrs, transmitted by direct head-to-head contact; fomite spread is overstated.
— Pediculus humanus corporis (body lice): lives in clothing seams, not on skin; associated with homelessness, crowding, poor hygiene; vector for Bartonella quintana, Rickettsia prowazekii (epidemic typhus), Borrelia recurrentis.
— Pthirus pubis (crab/pubic lice): pubic/axillary/eyelash hair; counts as a sexually transmitted infection — screen for concurrent STIs.
— Classical scabies: 10–15 mites total; intensely pruritic, worse at night; transmitted by prolonged skin-to-skin contact (>10 min) or shared bedding.
— Crusted (Norwegian) scabies: thousands to millions of mites; immunocompromised (HIV, HTLV-1, steroids, dementia, elderly in LTC); minimally pruritic, hyperkeratotic — extremely contagious, including via fomites.
— Outbreaks in schools, nursing homes, prisons, shelters, sports teams (wrestling).
— Generalized nocturnal pruritus, especially when household contacts also itch.
— Failure of "eczema" or "dermatitis" to respond to topical steroids.
— Sexually active patient with pubic itching → look for pubic lice and coexisting STIs.
Board pearl: Pruritus that wakes the patient from sleep and affects multiple household members is scabies until proven otherwise — even before you see a burrow.
— Scalp itching, especially occipital and retroauricular areas; cervical/occipital lymphadenopathy from scratching.
— Many children are asymptomatic; diagnosis triggered by school screening or parent finding nits.
— Ask about classroom outbreaks, recent sleepovers, shared hats/brushes (low-yield but commonly tested).
— Generalized pruritus, truncal excoriations along clothing seams (waistband, shoulders, axillae).
— History of homelessness, refugee camp, war zone, or no laundry access.
— Ask about fever, headache, splenomegaly → consider louse-borne typhus, relapsing fever, trench fever.
— Itching of pubic, perianal, thigh, axillary hair; eyelash involvement in children raises concern for sexual abuse.
— Sexual history: new partners, condom use, prior STIs; offer full STI panel (HIV, syphilis, GC/CT, hepatitis).
— Onset of itch 3–6 weeks after first infestation (sensitization to mite antigens); 1–3 days on reinfestation.
— Worse at night and after hot showers.
— Distribution: finger webs, flexor wrists, axillae, areolae, periumbilical, waistline, buttocks, genitals; spares head/neck in adults.
— In infants and elderly: head, neck, palms, soles are involved.
— Multiple household contacts itching is a near-pathognomonic clue.
— Thick, scaly, fissured plaques on hands, feet, scalp; nail dystrophy; often misdiagnosed as psoriasis or eczema.
— Minimal pruritus due to impaired immune response.
Key distinction: Scabies pruritus precedes visible findings and is out of proportion to exam; pediculosis itch is proportional to lice burden and localized to the infested area.
Step 3 management: Always document the sexual history in pubic lice and screen for HIV/syphilis/GC/CT — pubic lice is an STI marker, and missing co-infection is a frequent test trap.
— Live lice (2–3 mm, tan-gray, fast-moving) confirm active infestation — most sensitive single finding.
— Nits (oval, 0.8 mm, firmly cemented to hair shaft) within 6 mm of scalp suggest active infestation; nits >1 cm from scalp are usually nonviable (hair grows ~1 cm/month).
— Use a fine-toothed louse comb on wet, conditioned hair — the diagnostic gold standard in practice.
— Posterior cervical and occipital lymphadenopathy; impetiginized excoriations from scratching.
— Skin often appears normal between excoriations; examine clothing seams for lice and eggs.
— "Vagabond's skin": hyperpigmented, lichenified, excoriated trunk from chronic infestation.
— Crab-shaped lice grasping hair bases; macula cerulea — slate-blue 0.5–1 cm macules at bite sites (hemosiderin).
— Inspect eyelashes (phthiriasis palpebrarum) — especially in children.
— Burrow: thin, gray, serpiginous 2–10 mm line, often in finger webs or wrist flexor — pathognomonic.
— Erythematous papules, vesicles, excoriations in classic distribution.
— Scrotal/penile nodules in men, areolar nodules in women — highly suggestive.
— Acropustulosis on palms/soles in infants.
— Crusted scabies: hyperkeratotic plaques, especially subungual debris (mite reservoir).
Board pearl: Scabies in adults spares the head and back (above scapulae) but in infants under 2 and immunocompromised elders, head/neck/palm/sole involvement is the rule — a classic age-based exam pivot on Step 3 vignettes.
— Wet combing with a fine-toothed nit comb on conditioned hair, wiped on white paper, is more sensitive than dry visual inspection (sensitivity ~90% vs ~30%).
— Distinguish nits from hair casts, dandruff, hair product residue (these slide easily; nits are cemented).
— Wood's lamp: live nits fluoresce pale blue/white — useful in screening but not required.
— Confirmed: mites, eggs, or feces on microscopy or high-quality dermoscopy.
— Clinical: typical lesions in typical distribution + history of itch/contact.
— Suspected: atypical features but compatible history.
— Place mineral oil on an unexcoriated burrow or papule (KOH dissolves mite parts — avoid).
— Scrape with #15 blade until pinpoint bleeding; transfer to slide; look for mites, eggs, or scybala (feces) under low power.
— Sensitivity only ~50% in classical scabies because of low mite burden — a negative scrape does not rule out scabies.
— In crusted scabies, scrapings are teeming with mites — diagnosis is easy.
Step 3 management: When clinical suspicion is high but scraping is negative, treat empirically — empirical therapy is both diagnostic and therapeutic, especially in outbreak settings (school, nursing home, household with multiple itchy contacts). Do not delay treatment waiting for confirmatory studies.
— Delta-wing jet with contrail: dark triangle (mite anterior) trailing a linear burrow — pathognomonic for scabies, ~83–96% sensitive.
— Visible eggs and feces inside burrows.
— For lice: confirms live insects vs nits, helps avoid "no-nit policy" overdiagnosis.
— Apply fountain pen or surgical marker ink to suspected lesion, wipe with alcohol — ink tracks into the burrow and remains, highlighting it.
— In institutional outbreaks (LTC, prison, shelter): contact local public health, perform contact tracing, screen all residents and staff.
— Document onset timeline to identify index case.
Key distinction: Microscopy positive = confirmed scabies; clinical features alone with high pretest probability = clinical scabies — both warrant treatment. Don't let a negative scrape paralyze management.
Board pearl: Eyelash pubic lice (phthiriasis palpebrarum) in a prepubertal child mandates evaluation for sexual abuse and reporting to child protective services.
— Eradicate live parasites and eggs.
— Relieve symptoms (pruritus may persist 2–4 weeks post-treatment due to ongoing hypersensitivity — post-scabetic itch).
— Treat close contacts and decontaminate environment to prevent reinfestation.
— Identify and treat secondary infections (impetigo, cellulitis, post-strep glomerulonephritis after scabies-associated S. pyogenes).
— First-line: topical pediculicide + wet combing.
— Step up to oral ivermectin if topical treatments fail or resistance suspected.
— Cornerstone is hygiene and clothing decontamination (hot wash >50°C/130°F or discard); pediculicide rarely needed if clothing is treated.
— Topical permethrin or pyrethrin; treat sexual partners from prior 30 days; STI testing.
— Topical permethrin 5% OR oral ivermectin — both first-line.
— Treat all household members and close skin-to-skin contacts simultaneously, even if asymptomatic.
— Decontaminate bedding, clothing, towels used in past 3 days (hot wash + hot dryer, or bag in plastic ≥72 hours).
— Combination therapy: oral ivermectin (multiple doses) PLUS topical permethrin or benzyl benzoate.
— Isolation, contact precautions; involve infection control if institutional.
Step 3 management: For scabies, schedule a second dose at day 7–14 whether using permethrin or ivermectin — single-dose therapy does not kill newly hatched mites, and missing the repeat dose is the most common reason for "treatment failure" on Step 3 vignettes.
— Permethrin 1% cream rinse (OTC): apply to damp hair for 10 min, rinse; repeat day 9. Safe ≥2 months.
— Pyrethrins + piperonyl butoxide (OTC): avoid in chrysanthemum/ragweed allergy.
— Topical ivermectin 0.5% lotion (Sklice): single 10-min application; FDA-approved ≥6 months; no nit combing required.
— Spinosad 0.9% suspension: single 10-min application; ≥6 months.
— Benzyl alcohol 5%: ≥6 months; suffocates lice.
— Malathion 0.5% (Rx, ≥6 yrs): ovicidal, flammable, malodorous; reserved for resistance.
— Ivermectin 200–400 µg/kg PO, repeat day 7–10; for resistant cases or widespread outbreaks; ≥15 kg.
— Permethrin 1% or pyrethrins to affected areas × 10 min; repeat in 9–10 days.
— Eyelash involvement: petrolatum (Vaseline) ointment BID × 8–10 days; avoid neurotoxic agents near eyes.
— Permethrin 5% cream: apply neck-down (in adults), entire body in infants/elderly/immunocompromised; leave 8–14 hours, then wash off. Repeat in 7 days.
— Oral ivermectin 200 µg/kg: two doses, day 1 and day 8 (or day 14). Take with food (increases absorption). Equally effective; preferred in outbreaks and crusted scabies.
Board pearl: Post-scabetic pruritus can persist 2–4 weeks after successful eradication — do not retreat reflexively. Reserve retreatment for new burrows, new lesions, or contacts that were missed.
— Oral ivermectin 200 µg/kg on days 1, 2, 8, 9, 15 — and for severe cases days 22 and 29.
— PLUS topical permethrin 5% daily × 7 days, then 2×/week until clear, OR benzyl benzoate.
— Keratolytics (salicylic acid, lactic acid) to debride hyperkeratotic crusts → improves drug penetration.
— Trim and brush nails (subungual mite reservoir).
— Contact isolation until two consecutive negative skin scrapings.
— Declare outbreak with ≥2 epidemiologically linked cases; notify public health.
— Mass treatment of all residents, staff, and visitors with recent contact — symptomatic and asymptomatic alike — on the same day; repeat in 7–14 days.
— Environmental cleaning: launder linens hot wash + dryer; bag non-washables ×72 h; vacuum upholstery.
— Mites survive only ~24–36 hours off the host (longer in crusted scabies environments).
— Avoid in children <15 kg and pregnancy (limited safety data; alternative permethrin).
— Loa loa endemic regions: risk of encephalopathy with high microfilarial loads — not typically a US concern but tested.
— Drug interactions: minimal; CYP3A4 substrate.
— Local irritation, transient burning; rarely systemic.
— Safe in pregnancy (Category B) and infants ≥2 months.
— Permethrin-resistant head lice ("super lice") increasingly reported — switch to spinosad, topical ivermectin, or oral ivermectin.
— Suspected ivermectin-resistant scabies in crusted cases — escalate to combination therapy and longer courses.
CCS pearl: In a nursing home scabies outbreak CCS case, the orders flow is: isolate index → notify infection control and public health → mass treat all residents/staff with permethrin or ivermectin → environmental decontamination → repeat treatment day 7–14 → re-examine all at week 4. Skipping mass contact treatment is the most common scoring error.
— Higher risk for crusted scabies due to immunosenescence, dementia (impaired scratching), institutionalization.
— Atypical distribution — head, neck, scalp involvement is common; do not omit these areas during permethrin application.
— Pruritus may be absent or attributed to "senile xerosis" → diagnostic delay; consider scabies in any LTC resident with new rash or unexplained itch.
— Polypharmacy: ivermectin has minimal interactions but verify with warfarin (rare INR shifts reported).
— Permethrin: minimal systemic absorption (<2%), no dose adjustment needed in renal disease — preferred topical.
— Ivermectin: metabolized hepatically, <1% renal excretion — no dose adjustment for renal impairment, including dialysis.
— Ivermectin: limited data in severe hepatic dysfunction; use cautiously, but no specific dose adjustment recommended for mild–moderate disease.
— Permethrin preferred in advanced cirrhosis due to negligible systemic absorption.
— Application of topicals often requires caregiver assistance; ensure full body coverage including behind ears, umbilicus, gluteal cleft, genitals, subungual areas.
— Oral ivermectin may be preferred for adherence — single observed dose.
— Increased risk of secondary bacterial infection (impetigo, cellulitis, bacteremia) → lower threshold for antibiotics.
— Pressure injuries can be confused with scabies plaques and vice versa in bedbound patients.
— Treat empirically when exposed, even if asymptomatic, especially for crusted scabies index patient — staff transmission to other residents is the primary outbreak driver.
Step 3 management: In a demented LTC resident with refractory "eczema" or treatment-resistant pruritus, scrape early and treat empirically for scabies with oral ivermectin while awaiting results — empiric therapy is both diagnostic and preventive against ward-wide outbreak.
— First-line: permethrin 5% cream (Category B) — safe throughout pregnancy and breastfeeding; minimal systemic absorption.
— Sulfur 6–10% in petrolatum — oldest, safest, malodorous; alternative when permethrin unavailable.
— Avoid oral ivermectin in pregnancy when possible (limited human data, though emerging safety data are reassuring); avoid lindane absolutely.
— Breastfeeding: hold breastfeeding briefly after permethrin application to chest; resume after wash-off.
— Infants <2 months: sulfur ointment or permethrin 5% (off-label <2 mo but widely used and considered safe per AAP).
— Apply permethrin head-to-toe including scalp, face (avoiding eyes/mouth), ears in infants — distribution is different from adults.
— Ivermectin contraindicated in children <15 kg (~5 yrs) — blood-brain barrier concerns.
— Head lice: topical permethrin ≥2 months; spinosad and topical ivermectin ≥6 months; oral ivermectin ≥15 kg.
— No-nit school policies are no longer endorsed by AAP — children may return to school after first treatment.
— Pubic lice or scabies in a prepubertal child — particularly eyelash phthiriasis — warrants evaluation for sexual abuse and mandatory reporting to child protective services in all US states.
— Document findings carefully; involve child abuse pediatrics or social work.
— Treat as STI: partner notification, full STI panel, contraceptive counseling, HPV vaccination status review.
Board pearl: A pregnant patient with classical scabies → permethrin 5% × 2 applications 7 days apart, neck-down (or whole body), plus treat household contacts and partner simultaneously. Avoid ivermectin and lindane.
— Impetigo, ecthyma, cellulitis from scratching; usually Staphylococcus aureus or Streptococcus pyogenes.
— Treat with topical mupirocin (limited) or oral cephalexin/dicloxacillin; cover MRSA (TMP-SMX, clindamycin, doxycycline) in high-prevalence areas.
— Post-streptococcal glomerulonephritis (PSGN): scabies-associated S. pyogenes skin infection is a leading cause of PSGN globally, especially in Indigenous and tropical populations — check urinalysis if hematuria, edema, or HTN develops 1–3 weeks after impetiginized scabies.
— Rheumatic heart disease: emerging association via repeated streptococcal skin infections in endemic regions.
— Invasive infections: bacteremia, sepsis, endocarditis, osteomyelitis from chronic crusted scabies.
— Persists 2–4 weeks after eradication due to ongoing immune response to mite antigens.
— Manage with emollients, low–mid-potency topical steroids, oral antihistamines.
— Do not assume treatment failure unless new burrows or new lesions appear after 4 weeks.
— Persistent erythematous nodules on scrotum, penis, axillae, groin that can last months; immune granulomatous response, not active infection.
— Intralesional triamcinolone if symptomatic.
— Cervical and occipital lymphadenopathy; secondary pyoderma; rarely iron deficiency anemia from heavy body lice infestation.
— Vector-borne diseases from body lice: epidemic typhus (R. prowazekii), trench fever (B. quintana — also causes culture-negative endocarditis and bacillary angiomatosis), relapsing fever (B. recurrentis).
— Septicemia from bacterial superinfection — leading cause of mortality.
— Mortality 4× higher in untreated institutional outbreaks.
Key distinction: Persistent itch + new burrows = treatment failure or reinfestation → retreat. Persistent itch + no new lesions = post-scabetic pruritus → symptomatic management only.
— Diagnostic uncertainty after empiric treatment fails.
— Suspected crusted scabies, atypical distribution, or treatment-resistant cases.
— Recurrent infestations despite proper treatment and contact management — consider host immunodeficiency.
— Persistent scabies nodules requiring intralesional steroid.
— Crusted scabies in immunocompromised hosts (HIV, HTLV-1, transplant, hematologic malignancy).
— Institutional outbreak requiring coordinated mass treatment.
— Suspected louse-borne systemic infection (typhus, trench fever, relapsing fever).
— Outbreaks in schools, daycare, LTC, shelters, prisons, refugee camps — reportable in many jurisdictions.
— Crusted scabies in any congregate setting.
— Crusted scabies with sepsis, extensive secondary cellulitis, or systemic illness.
— Severe PSGN with renal failure or hypertensive emergency.
— Body lice with suspected epidemic typhus or relapsing fever — admit for IV doxycycline and supportive care; watch for Jarisch-Herxheimer reaction during relapsing fever treatment.
— Suspected child sexual abuse based on phthiriasis palpebrarum or pubic lice in a young child → involve child abuse pediatrics, social work, CPS report.
— Delusional parasitosis (formication without findings) — refer to psychiatry; treat with second-generation antipsychotics; resist the urge to repeat scabicide treatments.
CCS pearl: A bedbound nursing home patient with thick scaly plaques and fever — admit, draw blood cultures, start empiric anti-staphylococcal antibiotics (vancomycin), begin oral ivermectin + topical permethrin, place on contact isolation, and notify infection control and public health. The diagnosis is crusted scabies with bacteremia until proven otherwise.
— Chronic, relapsing, flexural distribution (antecubital/popliteal), personal/family atopy history.
— Responds to topical corticosteroids — scabies does not.
— Key distinction: eczema spares finger webs and genitals; scabies favors them.
— Sharp geometric borders matching exposure (jewelry, plant, cosmetic).
— Patch testing confirms; resolves with allergen avoidance.
— Tense vesicles on lateral fingers, palms, soles; can mimic scabies in adults.
— No burrows; no household contacts itching.
— Bedbug bites: linear "breakfast-lunch-dinner" clusters on exposed skin (face, arms, ankles); spare covered areas.
— Flea bites: ankles, lower legs.
— Mosquito/chigger: outdoor exposure history.
— Symmetric pruritic vesicles on extensor surfaces (elbows, knees, buttocks, scalp); associated with celiac disease; positive tissue transglutaminase IgA; direct immunofluorescence shows granular IgA at dermal papillae.
— Follicular pustules; trunk, thighs; Staphylococcus, Pseudomonas (hot tub), Malassezia.
— Seborrhea: greasy yellow scale, scalp itch, responds to ketoconazole.
— Hair casts and dandruff: easily slide off hair shafts.
— Annular plaque with scaly active border; KOH positive for hyphae.
— Polygonal violaceous papules, Wickham striae, oral involvement.
Board pearl: Any "treatment-resistant eczema" with nocturnal itch and itchy household contacts should be re-evaluated as scabies — repeating high-potency topical steroids on undiagnosed scabies worsens crusted disease and is a classic Step 3 distractor.
— Cholestatic liver disease (PBC, PSC, drug-induced): elevated ALP/GGT, bile acids; itch worse on palms/soles.
— Chronic kidney disease: uremic pruritus, especially in dialysis patients.
— Thyroid disease: hyperthyroidism causes generalized pruritus.
— Hematologic malignancies: Hodgkin lymphoma (aquagenic pruritus), polycythemia vera (post-bath itch), cutaneous T-cell lymphoma.
— Iron deficiency, diabetes, HIV (eosinophilic folliculitis).
— Medications: opioids, statins, ACEi, hydroxyethyl starch.
— CBC, CMP, TSH, LDH, HIV, hepatitis panel, ESR, age-appropriate cancer screening, chest X-ray if Hodgkin suspected.
— Delusional parasitosis: fixed false belief of infestation; "matchbox sign" (patient brings skin debris). Treat with risperidone/olanzapine; avoid validation by repeat scabicide.
— Notalgia paresthetica: localized upper-back itch, T2–T6 dermatome; neuropathic.
— Brachioradial pruritus: forearm itch worsened by sun, relieved by ice.
— Elderly with intense pruritus and urticarial plaques before bullae appear; direct immunofluorescence shows linear IgG/C3 at basement membrane.
— Eosinophilic folliculitis, papular pruritic eruption, scabies (often crusted) are all common in advanced HIV — always check HIV status in atypical or severe presentations.
— Fever + rash + homeless patient → consider epidemic typhus, trench fever, relapsing fever — treat with doxycycline.
Step 3 management: When generalized itch persists despite clear ectoparasite eradication and no primary lesions, pivot to systemic workup: CBC with differential, CMP, TSH, LDH, HIV, hepatitis, age-appropriate cancer screening — itch can precede lymphoma diagnosis by months.
— Treat all household members and close contacts simultaneously, even if asymptomatic (scabies and head lice).
— For scabies: launder all clothing, bedding, towels used in past 3 days in hot water (≥50°C/122°F) and high-heat dryer; non-washables sealed in plastic bag ≥72 hours (≥7 days for crusted scabies).
— Vacuum upholstery, mattresses, car seats; no need for fumigation sprays (low yield, toxic).
— Mites do not survive >36–72 hours off the host; lice <48 hours.
— Avoid head-to-head contact; don't share combs, hats, helmets, headphones.
— Routine school screening of asymptomatic children is not recommended by AAP.
— Wet combing every 2–3 days for 2 weeks can serve as both treatment and prevention.
— Treat all sexual partners from the past 30 days.
— Abstain from sexual contact until both partners completed treatment and asymptomatic.
— Complete STI testing and revaccinate (HPV, hepatitis B) as indicated.
— Discuss risk reduction: barrier protection, partner reduction, PrEP if appropriate.
— Regular bathing and clothing changes; access to laundry facilities.
— Connect to social services for housing-insecure patients — recurrence is inevitable without addressing root cause.
— Evaluate for underlying immunodeficiency (HIV, HTLV-1, lymphoma, iatrogenic immunosuppression).
— Ongoing surveillance — recurrence common; some patients require maintenance topical therapy.
— Children may return to school the day after first scabies treatment and after first lice treatment per AAP.
Step 3 management: The single most effective relapse-prevention intervention is simultaneous treatment of all close contacts plus environmental decontamination on the same day. Sequential or staggered treatment guarantees ping-pong reinfestation — a high-yield Step 3 management vignette pitfall.
— Scabies: clinic visit or telehealth check at 2 weeks and 4 weeks post-initial treatment.
— Reassess for new burrows or new lesions; do not retreat for residual itch alone.
— Head lice: parental wet-combing checks every 2–3 days for 2 weeks; clinician follow-up if persistent live lice.
— Pubic lice: STI test results review; reassess at 1–2 weeks.
— New burrows or new papules after 2 weeks.
— Persistent live mites on scraping.
— Failure to treat contacts — biggest cause.
— Inadequate application (missed scalp in infants, subungual area in crusted scabies, behind ears).
— Untreated contacts → reinfestation.
— Missed second dose at day 7–14.
— True resistance (rare; consider alternative agent — oral ivermectin if topical failed, or vice versa).
— Itch may persist 2–4 weeks even after successful treatment — emphasize this to prevent unnecessary retreatment.
— Provide written instructions with body-area diagram for permethrin application.
— Avoid hot showers immediately before applying permethrin (increases systemic absorption).
— For head lice: emphasize that lice do not jump or fly — only direct contact transmits.
— Destigmatize: head lice and scabies are not signs of poor hygiene.
— Urinalysis at 1–3 weeks if impetiginized scabies (screen for PSGN).
— Skin reassessment for secondary bacterial infection.
— In LTC outbreaks: surveillance scrapings for 6 weeks; staff symptom monitoring.
— Avoid unnecessary lab testing; both diagnoses are clinical.
— Avoid prolonged "no-nit" school exclusion — costs families work/school days without infection-control benefit.
Board pearl: A patient returns 3 weeks after permethrin saying "I still itch" but has no new lesions and contacts were treated — prescribe topical steroid and antihistamine, reassure, do not retreat. Reflex retreatment is the wrong answer.
— Pubic lice or scabies in a prepubertal child, especially phthiriasis palpebrarum (eyelash lice), mandates evaluation for sexual abuse and mandatory report to child protective services in all 50 US states.
— Document carefully, involve child abuse pediatrician, social work, and law enforcement per institutional protocol.
— Mandated reporters are legally protected when reporting in good faith.
— Institutional outbreaks (LTC, schools, prisons, shelters) are reportable in many states; check local jurisdiction.
— Notification triggers infection-control coordination, mass treatment, and resource allocation.
— Avoid stigmatizing language ("dirty," "infested") — both conditions occur across all socioeconomic strata.
— Maintain confidentiality of pubic lice/STI diagnoses, particularly for adolescents — most states permit minors to consent to STI evaluation and treatment without parental notification.
— Most US states allow minors ≥12–14 to consent to STI testing and treatment confidentially; know your state's age of consent.
— Document confidential discussions appropriately; insurance EOBs to parents may inadvertently disclose — discuss with patient.
— Mass treatment in nursing homes/prisons: residents who can consent should be informed; for those who cannot, follow surrogate decision-maker process. Public health authority may override individual refusal during outbreaks in some jurisdictions.
— Discharging a crusted scabies patient back to LTC without notifying receiving facility is a major patient-safety failure — risks ward-wide outbreak. Communicate diagnosis in handoff and on transfer paperwork.
— Failure to treat household contacts at discharge = guaranteed readmission/recurrence.
— Healthcare workers exposed to crusted scabies → empiric prophylactic treatment (permethrin or single-dose ivermectin) per OSHA/CDC guidance.
— AAP and CDC oppose "no-nit" policies — keeping children out of school harms education without preventing transmission.
Step 3 management: When transferring a patient with crusted scabies to a SNF, explicitly document the diagnosis, isolation requirements, and treatment plan on the transfer summary and call the receiving facility — failure to do so is both a patient safety event and a potential liability issue.
Board pearl: When the vignette mentions "homeless patient with fever, headache, and rash" — think body lice + typhus → treat with doxycycline, not just permethrin.
— Vignette: 35-yo with 3 weeks of severe night itch in finger webs and waistline; spouse and children also itching. Answer: scabies — permethrin 5% to all household members + repeat in 7 days + decontaminate linens.
— Elderly LTC resident with months of "eczema" unresponsive to triamcinolone; thick scaly plaques on hands. Answer: crusted scabies — oral ivermectin days 1, 2, 8, 9, 15 + topical permethrin + contact isolation + infection-control notification.
— Wet combing reveals 2-mm tan insect. Answer: head lice — permethrin 1% topical, repeat day 9; child may return to school after first treatment.
— Answer: pubic lice + full STI panel (HIV, RPR, GC/CT, hepatitis); treat partners ≥30 days; permethrin 1%.
— Answer: epidemic typhus (R. prowazekii) — doxycycline 100 mg PO BID; address lice via clothing decontamination.
— Answer: post-scabetic pruritus — antihistamines, topical steroids, reassurance; do not retreat.
— Answer: petrolatum to eyelashes BID × 8 days + evaluate for sexual abuse + report to CPS.
— Answer: permethrin 5%, repeat in 7 days; avoid ivermectin and lindane.
— Answer: mass treatment of all residents/staff with permethrin or oral ivermectin on same day, repeat day 7–14, environmental decontamination, notify public health, contact precautions for crusted index case.
— Answer: PSGN — check BP, UA, complement, ASO; supportive management.
Key distinction: Watch for the answer trap "retreat scabies" in vignettes describing residual itch without new lesions — the correct answer is symptomatic management, not re-application of scabicide.
The Bottom Line: Lice and scabies are clinical diagnoses requiring simultaneous treatment of the patient, all close contacts, and the environment — permethrin or ivermectin remain first-line, post-scabetic itch is expected and not a treatment failure, and atypical presentations should trigger consideration of crusted scabies, immunodeficiency, or sexual abuse.
Board pearl: The single most testable management principle across this entire topic is simultaneous same-day treatment of patient + all close contacts + environment + scheduled repeat dose at 7–14 days — answer choices that omit any of these four pillars are wrong on Step 3 vignettes.