Signs and Symptoms of Scabies
The predominant symptom of scabies is intense pruritus (itching), characteristically worse at night, often appearing out of proportion to visible skin findings. 1
Classic Presentation
Primary Symptom
- Intense nocturnal pruritus is the hallmark feature, typically affecting all body regions except the head in adults 1, 2
- Itching may take several weeks to develop with first infestation, but can occur within 24 hours after subsequent reinfestations due to sensitization to Sarcoptes scabiei 1
Skin Lesions
Pathognomonic findings:
- Burrows (serpiginous tracks, usually up to 1 cm in length) are the diagnostic hallmark when present 3, 2, 4
- These represent the mite tunneling through the stratum corneum 3
Non-specific findings:
- Erythematous papules and macules with excoriation 3, 2, 4
- Vesicles may be present 3, 4
- Inflammatory changes in intertriginous areas 1
Distribution Pattern
Typical sites of involvement include: 3, 4
- Finger webs and lateral aspects of fingers
- Volar wrists
- Extensor surfaces of elbows and knees
- Axillary folds
- Abdomen, waist, and navel
- Buttocks and groins
- Inframammary folds in women
- Genitalia in men
Important caveat: The scalp is rarely infested in adults, but the hairline, neck, temple, and forehead may be affected in infants and geriatric patients 5
Atypical Presentations
Debilitated or Elderly Patients
The clinical presentation can be highly atypical in nursing home residents and debilitated patients: 1
- Burrows may be absent
- Inflammatory changes may be minimal or absent
- Pruritus may be absent
- May present only with hyperkeratosis, papules, or vesicles
Clinical pearl: Diagnosis is often made retrospectively when the typical rash occurs in healthcare workers or visitors who had contact with the patient 1
Crusted (Norwegian) Scabies
This severe variant occurs primarily in immunocompromised hosts: 1, 6, 4
- Characterized by dry, scaly, hyperkeratotic, and crusted skin, particularly on extremities
- Pruritus may be reduced or completely absent 2, 6
- Patients are heavily infested with mites
- Highly contagious due to large mite burden
Diagnostic Clues from History
Key historical features that should raise suspicion: 2
- Intense itch worse at night
- Itch appearing out of proportion to physical findings
- Close contacts (household members, sexual partners) also experiencing itching 2
- Symptoms in multiple family members or institutional contacts 1
Transmission Context
- Scabies in adults is frequently sexually acquired 1, 6
- In children, transmission is usually non-sexual 1
- Spread occurs through prolonged skin-to-skin contact or contaminated fomites 1, 4
Common Pitfalls in Recognition
Be aware that: 1
- An incorrect diagnosis can lead to pseudo-outbreaks with widespread "psychogenic" scabies (itching without skin lesions)
- Diagnosis may need to be made on clinical findings alone when microscopy is unavailable
- Persistent pruritus after treatment (up to 2 weeks) does not indicate treatment failure 7, 8, 5