A 32-year-old woman presents with severe pruritus, worse at night, affecting her wrists, interdigital spaces, and axillae for 3 weeks. Examination reveals linear burrows and erythematous papules. Her 6-year-old daughter and husband have identical lesions. KOH mount of burrow scrapings shows mites, eggs, and fecal pellets. What is the most appropriate next step in management?

Explanation

## Scabies Management: Principles and Next Steps ### Diagnosis Already Confirmed **Key Point:** The clinical presentation (burrows, night pruritus, interdigital involvement) combined with positive microscopy (mites, eggs, fecal pellets on KOH mount) establishes definitive diagnosis. No further diagnostic testing is needed. ### Why Simultaneous Household Treatment is Mandatory **High-Yield:** Scabies is highly contagious; the incubation period is 2–6 weeks. All household members with or without symptoms must be treated simultaneously to prevent reinfection cycles. Treating only the index patient guarantees treatment failure. **Clinical Pearl:** The presence of identical lesions in the daughter and husband confirms household transmission and mandates contact treatment. ### Treatment Protocol | Step | Action | Rationale | |------|--------|----------| | **1. Topical agent** | Permethrin 5% cream (first-line in non-pregnant, non-immunocompromised) | Safe, effective, low systemic absorption | | **2. Application** | Apply to entire body surface (neck to toes); repeat after 7 days | Ensures complete mite coverage; second application kills newly hatched mites | | **3. Household contacts** | Treat simultaneously (all family members, close contacts) | Prevents reinfection | | **4. Environmental measures** | Wash clothes, bedding, towels at ≥50°C; seal non-washables for 72 hours | Mites cannot survive >72 hours off skin | | **5. Pruritus management** | Continue antihistamines/topical steroids for 2–4 weeks post-treatment | Post-scabetic pruritus persists due to mite antigen residue | **Mnemonic:** **SCABIES management = Simultaneous treatment, Contacts included, Apply permethrin, Bedding/clothes wash, Inspect in 2 weeks, Environmental isolation, Second application at 7 days** ### Why Other Options Are Suboptimal **Option 0 (Patient alone):** Treating only the index patient while household contacts remain untreated guarantees reinfection within 2–6 weeks. This is a common exam trap. **Option 2 (Dermoscopy before treatment):** Diagnosis is already confirmed by microscopy. Dermoscopy is useful when microscopy is unavailable or inconclusive, not after positive KOH mount. **Option 3 (Ivermectin first-line):** Oral ivermectin is reserved for crusted scabies, immunocompromised patients, or when topical agents are contraindicated (pregnancy, extensive disease). In an immunocompetent, non-pregnant patient with uncomplicated scabies, permethrin is first-line. [cite:Irvine 26e Ch 7; Park 26e Ch 6]