Scabies

Diagnosis: Scabies

Scabies

Clinical Presentation

Scabies

Clinical History

Intense generalized pruritus (worse at night), with characteristic distribution: web spaces, wrists, axillae, waistline, genitalia. Close contacts with similar symptoms.

Treatment

Permethrin 5% cream (apply neck down, wash off after 8-14 hours, repeat in 1 week). Oral ivermectin 200 mcg/kg (days 1 and 8). Crusted scabies: combination permethrin + oral ivermectin + keratolytics. Wash bedding/clothing in hot water. Treat all contacts.

Differential Diagnosis

• Atopic dermatitis • Contact dermatitis • Insect bites • Dermatitis herpetiformis • Prurigo nodularis • Bullous pemphigoid • Drug eruption

Key Learnings

• Caused by Sarcoptes scabiei var. hominis — obligate human parasite • Pruritus is an allergic reaction to mite proteins — may take 2-6 weeks to develop in first infection • Pathognomonic finding: burrow (S-shaped or linear tunnel) in web spaces, wrists, elbows • Crusted (Norwegian) scabies: massive mite burden in immunocompromised — highly contagious • Treat all household contacts simultaneously even if asymptomatic • Post-treatment pruritus may persist for 2-4 weeks — does not indicate treatment failure • Dermoscopy: "delta wing" or "hang glider" sign (triangular, brown structure = mite head) • Nodular scabies: persistent pruritic nodules (hypersensitivity reaction) may persist for months after treatment

Tags: dermatologist, dermatology, kodachrome, Scabies