Overview
Definition
An intensely pruritic skin infestation caused by the microscopic mite Sarcoptes scabiei var. hominis.
Epidemiology
Very common worldwide, especially in crowded environments (nursing homes, prisons, schools) and developing countries.
Etiology & Risk Factors
- Infestation by the female Sarcoptes scabiei mite, which burrows into the stratum corneum to lay eggs
Clinical Symptoms
- Intense pruritus (itching), characteristically worse at night (allergic reaction to mite feces/saliva)
- Small, erythematous papules and linear 'burrows' (gray-white threadlike lines)
- Distribution: Web spaces of fingers, flexor wrists, axillae, beltline, and genitalia
- Crusted Scabies (Norwegian Scabies): Hyperkeratotic crusted plaques containing millions of mites, occurring in immunocompromised hosts, highly contagious but often non-itchy
Clinical Approach
Diagnosis
- Clinical presentation and distribution of lesions
- Skin scraping of a burrow showing mites, eggs, or scybala (feces) under microscopy
Management
- Topical Permethrin 5% cream (applied neck-to-toe, left on for 8-14 hours, repeated in 1 week)
- Oral Ivermectin (indicated for crusted scabies, mass outbreaks, or permethrin failure)
- Treat all close contacts and wash all clothing/bedding in hot water
Complications
- Secondary bacterial infection (Streptococcal/Staphylococcal impetigo, which can lead to post-streptococcal glomerulonephritis)
- Crusted scabies outbreaks