The candle spot phenomenon refers to the appearance of scales falling off like candle wax when a skin lesion, typically associated with psoriasis, is gently scraped. This is a visual sign indicative of hyperkeratosis and parakeratosis of the epidermis.
Understanding the Candle Spot Phenomenon
The candle spot sign, also known as the wax-spot sign, is a diagnostic feature observed when examining certain skin conditions, most notably psoriasis. Here’s a breakdown:
- Appearance: The lesions are generally covered with silvery-white scales.
- Observation: When these scales are gently scraped, they detach in a manner reminiscent of candle wax flaking off.
- Underlying Cause: This specific scaling pattern results from abnormalities in the skin's outer layer (epidermis). These abnormalities include:
- Hyperkeratosis: An abnormal thickening of the stratum corneum (outermost layer of the epidermis).
- Parakeratosis: Retention of nuclei in the stratum corneum cells, indicating incomplete keratinization.
Clinical Significance
The candle spot phenomenon is a valuable clinical sign that helps dermatologists in the diagnosis of psoriasis. When combined with other clinical features (e.g., Auspitz sign, distribution of lesions) and, if necessary, histopathological examination, it aids in confirming the diagnosis. While not exclusive to psoriasis, its presence strongly suggests the condition.
Differential Diagnosis
While the candle spot phenomenon is most strongly associated with psoriasis, it is important to consider other conditions in the differential diagnosis. These might include:
- Seborrheic dermatitis
- Tinea corporis (ringworm)
- Eczema
Conclusion
The candle spot phenomenon, characterized by the candle wax-like scaling upon gentle scraping of psoriatic lesions, is a key clinical indicator of hyperkeratosis and parakeratosis in the epidermis. It serves as a helpful diagnostic sign for psoriasis, alongside other clinical findings.
