Model Answer
0 min readIntroduction
Pruritic papular eruptions are common dermatological presentations, requiring a thorough examination to establish an accurate diagnosis. The described clinical picture – itchy, discrete, flat-topped, skin-coloured to violaceous papules on the ankles, wrists, and forearms – strongly suggests a diagnosis within the spectrum of papulosquamous dermatoses. While lichen planus is a leading consideration, other conditions like pityriasis rosea, secondary syphilis, and drug eruptions must be ruled out. A comprehensive examination beyond the initially affected areas is essential to identify subtle clues that will lead to a definitive diagnosis.
Systematic Examination Plan
To arrive at a clinical diagnosis, a thorough examination beyond the initially described areas is crucial. The following areas should be examined systematically:
1. Skin Examination – Beyond Initial Sites
- Flexural Areas: Examine the flexural surfaces of elbows, knees, and groin. Lichen planus frequently involves these areas.
- Trunk & Scalp: Inspect the trunk for any similar lesions or evidence of preceding lesions (e.g., a herald patch in pityriasis rosea). The scalp should be examined for scaling or inflammation.
- Palms & Soles: Lichen planus can affect the palms and soles, presenting as hyperkeratotic papules.
- Nail Changes: Examine all nails for longitudinal ridging, pitting, subungual hyperkeratosis, or onycholysis, which are common in lichen planus.
- Oral Mucosa: This is critical. Lichen planus frequently presents with white, lacy lesions (Wickham’s striae) on the buccal mucosa.
- Genital Mucosa: Examine the genital mucosa for erosions or white plaques, as lichen planus can also affect this area.
- Previous Scar Sites: Koebner phenomenon (lesions developing at sites of trauma) can be observed in lichen planus.
2. Lymph Node Examination
Palpate regional lymph nodes (axillary, epitrochlear, inguinal) for any enlargement or tenderness. Lymphadenopathy is not typical of lichen planus but may be present in other conditions.
3. Systemic Examination (Brief)
A brief systemic examination, including vital signs, is important to rule out systemic causes of skin eruptions. This includes checking for fever, which might suggest a secondary infection or systemic illness.
4. Differential Diagnosis Considerations
- Lichen Planus: The most likely diagnosis given the presentation. Look for Wickham’s striae in the mouth.
- Pityriasis Rosea: Look for a herald patch – a larger, solitary lesion that precedes the widespread eruption.
- Secondary Syphilis: Consider this, especially if there is a history of unprotected sexual activity. Look for lesions on palms and soles, which are characteristic.
- Drug Eruption: A detailed medication history is crucial.
- Atopic Dermatitis: While less likely with this presentation, consider if there is a personal or family history of atopy.
5. Diagnostic Aids (If Available)
While a clinical diagnosis is often possible, consider these if the diagnosis remains uncertain:
- Skin Biopsy: Histopathology can confirm the diagnosis of lichen planus, showing characteristic band-like lymphocytic infiltrate at the dermoepidermal junction.
- Serological Tests: If syphilis is suspected, perform a VDRL or RPR test.
| Feature | Lichen Planus | Pityriasis Rosea | Secondary Syphilis |
|---|---|---|---|
| Morphology | Flat-topped, polygonal, violaceous papules | Oval, scaly plaques with central clearing | Maculopapular rash, often on palms/soles |
| Distribution | Flexural areas, wrists, ankles | Trunk, “Christmas tree” pattern | Generalized, including palms/soles |
| Oral Involvement | Common (Wickham’s striae) | Rare | Rare |
| Nail Changes | Common | Rare | Alopecia, nail changes |
Conclusion
In conclusion, a 30-year-old female presenting with itchy, flat-topped papules requires a comprehensive dermatological examination extending beyond the initial sites of involvement. Systematic assessment of flexural areas, mucous membranes, nails, and scalp, coupled with consideration of differential diagnoses like lichen planus, pityriasis rosea, and secondary syphilis, is crucial. A skin biopsy may be necessary to confirm the diagnosis and guide appropriate management. Early and accurate diagnosis is essential for effective treatment and prevention of potential complications.
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.