Model Answer
0 min readIntroduction
Scabies is a contagious skin infestation caused by the microscopic mite *Sarcoptes scabiei var. hominis*. It’s characterized by intense pruritus (itching) and a distinctive skin rash. The mites burrow into the upper layer of the skin where they live and lay their eggs, leading to an inflammatory response. While often associated with poor hygiene, scabies can affect people of all socioeconomic backgrounds. Understanding the clinical presentation and potential complications is crucial for prompt diagnosis and effective treatment, preventing further spread and minimizing morbidity. This answer will detail the primary manifestations, lesion distribution, and complications of scabies in adults.
Primary Manifestations of Scabies
The hallmark symptom of scabies is intense, generalized pruritus, which is often worse at night. This is due to the allergic reaction to the mites, their feces, and eggs. The primary skin manifestations include:
- Burrows: These are slightly raised, serpiginous (snake-like) tracks on the skin, representing the tunnels created by the female mites. They are typically 2-10 mm long and grayish-white in color.
- Papules: Small, red bumps that represent inflammatory reactions to the mites.
- Vesicles: Small, fluid-filled blisters, often found at the ends of burrows.
- Excoriations: Scratch marks resulting from intense itching.
- Nodules: Firm, itchy bumps, particularly common in scabies norvegica (crusted scabies).
Pattern of Distribution of Lesions on the Body
The distribution of lesions in scabies is characteristic, although it can vary slightly based on age, sex, and immune status. In adults, the most common sites of involvement include:
- Interdigital spaces: Between the fingers and toes. This is a highly characteristic location.
- Wrists: Especially the volar (palm-side) surface.
- Axillae: Armpits.
- Periareolar region: Around the nipples.
- Umbilicus: Navel.
- Genitalia: Particularly the penis in males.
- Buttocks:
- Belt line:
In immunocompromised individuals, the distribution may be more widespread and atypical.
Complications of Scabies
Untreated or complicated scabies can lead to several complications:
Secondary Bacterial Infections
Intense scratching can break the skin, allowing bacteria (typically *Staphylococcus aureus* or *Streptococcus pyogenes*) to enter, leading to impetigo, cellulitis, or even more serious infections like sepsis. This is a common complication, especially in children.
Crusted Scabies (Scabies Norvegica)
This is a severe form of scabies that occurs in immunocompromised individuals (e.g., HIV/AIDS, organ transplant recipients, those on immunosuppressive medications) or in elderly or debilitated patients. It is characterized by thick, crusted lesions containing a massive number of mites. Crusted scabies is highly contagious and often presents with minimal itching initially, delaying diagnosis.
Post-Scabetic Itch
Even after successful treatment, some individuals may experience persistent itching for weeks or months. This is thought to be due to a hypersensitivity reaction to dead mites or their products.
Glomerulonephritis
Rarely, scabies can be associated with post-streptococcal glomerulonephritis, an inflammation of the kidney’s filtering units.
Rheumatic Fever-like Syndrome
In some cases, scabies has been linked to a rheumatic fever-like syndrome, characterized by joint pain, fever, and inflammation.
Eczematization
Chronic scratching can lead to lichenification (thickening of the skin) and eczema-like changes.
| Complication | Description | Risk Factors |
|---|---|---|
| Secondary Bacterial Infection | Impetigo, cellulitis, sepsis due to skin breakdown from scratching. | Intense itching, poor hygiene, compromised skin barrier. |
| Crusted Scabies | Severe form with thick, crusted lesions and a high mite load. | Immunocompromise, elderly, debilitated patients. |
| Post-Scabetic Itch | Persistent itching after successful treatment. | Hypersensitivity to mite antigens. |
Conclusion
In conclusion, scabies presents with characteristic clinical features – intense pruritus and a specific rash distribution – and can lead to significant complications if left untreated. Recognizing the primary manifestations, understanding the typical lesion patterns, and being aware of potential sequelae like secondary infections and crusted scabies are essential for timely diagnosis and appropriate management. Public health measures focusing on prompt treatment of affected individuals and their close contacts are crucial to control the spread of this highly contagious condition.
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.