Characteristics of Scabies Rash
Scabies presents as a pruritic papular eruption with pathognomonic burrows in characteristic body locations, accompanied by intense nocturnal itching that is often out of proportion to visible skin findings. 1, 2
Primary Clinical Features
Distribution Pattern
- Classic scabies affects specific body regions while characteristically sparing the head in adults: finger webs, volar wrists, lateral aspects of fingers, extensor surfaces of elbows and knees, axillary folds, waist, navel, abdomen, buttocks, inframammary folds, and male genitalia 1, 3, 4
- In infants and geriatric patients, the scalp, hairline, neck, temple, and forehead may be infested, unlike in typical adults 1, 5
Morphology of Lesions
- The pathognomonic sign is the presence of burrows—serpiginous linear tracks typically up to 1 cm in length where the mite has burrowed into the epidermis 1, 2, 4
- Nonspecific lesions include erythematous papules, vesicles, plaques, and excoriations distributed in the characteristic locations 3, 6, 4
- Bedbug bites present as linear pruritic papules (a key distinguishing feature), while scabies shows a more generalized distribution 6
Characteristic Symptoms
- Intense nocturnal pruritus is the hallmark symptom, typically worse at night and often appearing out of proportion to the physical findings 1, 2, 4
- The itch affects all body regions except the head in adults 2
- A close contact also experiencing itching strongly supports the diagnosis 2
Atypical Presentations
Crusted (Norwegian) Scabies
- Characterized by dry, scaly, hyperkeratotic and crusted skin, particularly on the extremities, rather than the typical papular rash 2, 4
- May not be itchy, which is a critical distinguishing feature from classic scabies 2
- Occurs in immunodeficient, debilitated, or malnourished persons and harbors thousands to millions of mites (versus 10-15 in classic scabies) 7
Other Variants
- Nodular scabies presents with persistent pruritic nodules 4
- Bullous scabies may occur, particularly in certain populations 4
- In debilitated or elderly patients, burrows and pruritus may be absent, with only hyperkeratosis, papules, or vesicles present 1
Post-Treatment Considerations
- Rash and pruritus commonly persist for up to 2 weeks after successful treatment—this is NOT treatment failure and does NOT indicate need for retreatment 1, 8, 5
- Approximately 75% of patients who continued to manifest pruritus at 2 weeks had cessation by 4 weeks 5
- Demonstrable living mites after 14 days indicate that retreatment is necessary 1, 5
Diagnostic Approach
- Diagnosis is primarily clinical, based on the characteristic triad of burrows, pruritic rash in typical locations, and nocturnal itching 1
- Confirmation requires microscopic or dermatoscopic identification of mites, eggs, or fecal pellets from skin scrapings 1, 4
- A history of intense itch worse at night, affecting all body regions except the head, with a close contact also itching, should prompt serious consideration of scabies 2