Model Answer
0 min readIntroduction
Scabies is a contagious skin infestation caused by the mite *Sarcoptes scabiei*. Typically, it presents with intense pruritus (itching), particularly at night, and a characteristic rash involving interdigital spaces, wrists, and genitalia. However, scabies can manifest atypically, leading to diagnostic delays and inappropriate treatment. These atypical presentations are particularly common in infants, the elderly, immunocompromised individuals, and those with altered hygiene practices. Recognizing these variations is crucial for prompt diagnosis and effective public health control.
Atypical Presentations of Scabies
The classic presentation of scabies isn't always observed. Several factors can alter the clinical picture, leading to atypical manifestations.
1. Scabies in Infants and Young Children
- Burrowing on Palms and Soles: Unlike adults, infants and young children often present with burrows on the palms and soles.
- Vesiculobullous Lesions: The rash can be predominantly vesicular or bullous, mimicking other blistering dermatoses.
- Crusted Scabies Mimicking Other Conditions: Severe infestations can resemble eczema or impetigo.
2. Scabies in the Elderly and Immunocompromised Individuals
- Crusted (Norwegian) Scabies: This is a hyperinfestation occurring in individuals with impaired cell-mediated immunity (e.g., HIV/AIDS, leukemia, organ transplant recipients, elderly). It’s characterized by thick, crusted scales containing a massive number of mites. Pruritus may be absent or minimal.
- Atypical Distribution: The rash may be more widespread and less localized to typical sites.
- Diagnostic Difficulty: The crusted nature can make it difficult to identify burrows or mites microscopically.
3. Scabies with Atypical Morphology
- Erythematous Papules without Burrows: Some individuals may present with generalized erythematous papules without visible burrows, resembling drug eruptions or other papular dermatoses.
- Urticarial Scabies: An allergic reaction to the mites can cause urticaria (hives) as the primary manifestation.
- Pustular Scabies: Secondary bacterial infection can lead to pustules, mimicking bacterial folliculitis.
4. Scabies in Specific Locations
- Head Scabies: Common in infants and immunocompromised individuals, presenting with scalp involvement.
- Genital Scabies: Can present as isolated lesions on the genitalia, leading to misdiagnosis as sexually transmitted infections.
- Nail Scabies: Rare, but can occur, presenting as subungual hyperkeratosis and onycholysis.
5. Incognito Scabies
This refers to scabies that has been modified by topical corticosteroids, often used for presumed eczema. This can mask the typical clinical features, making diagnosis challenging. The rash may become less itchy and more diffuse, with atypical morphology.
Diagnostic Considerations
Diagnosis of atypical scabies relies on a high index of suspicion. Skin scraping for microscopic examination remains the gold standard, but may be negative in crusted scabies or incognito scabies. Multiple scrapings from different sites are recommended. PCR testing for *Sarcoptes scabiei* DNA is increasingly available and offers higher sensitivity. Clinical context and epidemiological factors are crucial in guiding diagnosis.
Conclusion
Atypical presentations of scabies pose a significant diagnostic challenge. Recognizing these variations, particularly in vulnerable populations like infants, the elderly, and immunocompromised individuals, is essential for timely and accurate diagnosis. A thorough clinical examination, coupled with appropriate diagnostic testing, is crucial to avoid misdiagnosis and ensure effective treatment, preventing further spread of this highly contagious infestation. Public health awareness and education regarding atypical presentations are also vital.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.