Model Answer
0 min readIntroduction
A lichenoid tissue reaction is a specific pattern of inflammation seen under microscopic examination of skin biopsies. It’s characterized by damage to the basal keratinocytes (the cells at the bottom of the epidermis) along with a dense band of lymphocytes (a type of white blood cell) at the dermo-epidermal junction. This pattern is not specific to a single disease but is seen in a variety of inflammatory skin conditions. Identifying the disease that best exemplifies this reaction pattern is crucial for understanding and diagnosing these conditions.
The Prototype: Lichen Planus
The disease that is considered the prototype of a lichenoid reaction is Lichen Planus (LP). It’s the classic example used to define and understand this histological pattern.
Histopathological Features of Lichen Planus
The hallmark histological features of Lichen Planus, which define the lichenoid reaction pattern, include:
- Basal Cell Vacuolization: Damage and swelling of the basal keratinocytes.
- Liquefactive Degeneration of Basal Cells: Breakdown of the basal keratinocytes.
- Dense Band-like Lymphocytic Infiltrate: A thick band of lymphocytes hugging the dermo-epidermal junction.
- Saw-toothing of the Dermo-Epidermal Junction: An irregular, jagged appearance of the junction between the dermis and epidermis.
- Melanin Incontinence: Melanin pigment accumulating in the dermal papillae.
Clinical Presentation of Lichen Planus
Lichen Planus typically presents as:
- Pruritic, Flat-topped Papules: Itchy, flat-topped bumps.
- Polygonal Shape: The papules often have a polygonal shape.
- Wickham's Striae: Fine, white lines on the surface of the papules, visible upon close inspection.
- Common Sites: Flexural areas (wrists, ankles), oral mucosa, and genitalia.
Variants of Lichen Planus
While classic Lichen Planus is the prototype, several variants exist, all demonstrating the underlying lichenoid reaction pattern:
- Erosive Lichen Planus: Affects the oral mucosa, causing painful erosions.
- Linear Lichen Planus: Presents as linear streaks, often following scratches or trauma.
- Annular Lichen Planus: Forms ring-shaped lesions.
- Pigmentary Lichen Planus: Results in post-inflammatory hyperpigmentation.
Differential Diagnosis
Other conditions that can exhibit a lichenoid reaction pattern include:
- Drug eruptions
- Graft-versus-host disease
- Lupus erythematosus
- Certain eczematous dermatitides
However, Lichen Planus remains the gold standard and prototypical example for recognizing and understanding this histological pattern.
Conclusion
In conclusion, Lichen Planus is unequivocally the disease that serves as the prototype for a lichenoid tissue reaction. Its characteristic histopathological features – basal cell vacuolization, a dense lymphocytic infiltrate, and saw-toothing of the dermo-epidermal junction – define this reaction pattern. Recognizing this pattern is crucial for dermatologists in diagnosing a range of inflammatory skin conditions, with Lichen Planus serving as the foundational example.
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.