Apple jelly nodule on diascopy, is a feature of: March 2011
**Core Concept**
Apple jelly nodule on diascopy is a clinical sign used to diagnose a specific skin condition. It is characterized by the appearance of a yellowish or reddish-brown nodule on the skin when pressure is applied. This sign is associated with a particular type of skin lesion that contains a high number of blood vessels.
**Why the Correct Answer is Right**
The apple jelly nodule is a classic sign of xanthoma or xanthelasma when diascopy is performed. When diascopy is applied to the affected area, the nodule turns into a yellowish or reddish-brown color resembling apple jelly. This is due to the high concentration of lipid-laden macrophages (foam cells) and the presence of numerous blood vessels in the affected skin. The foam cells and blood vessels give the skin its characteristic yellowish or reddish hue.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the apple jelly nodule is not a feature of melanoma. Melanoma is a type of skin cancer that does not typically exhibit this sign.
**Option B:** This option is incorrect because the apple jelly nodule is not a feature of basal cell carcinoma. Basal cell carcinoma is a type of skin cancer that may present with different clinical signs, but not typically with an apple jelly nodule.
**Option C:** This option is incorrect because the apple jelly nodule is not a feature of psoriasis. Psoriasis is a chronic skin condition that may present with different clinical signs, but not typically with an apple jelly nodule.
**Clinical Pearl / High-Yield Fact**
When performing diascopy on a skin lesion, it is essential to note the color change and texture of the lesion. The apple jelly nodule is a classic sign of xanthoma or xanthelasma, and recognizing this sign can help diagnose the condition accurately.
**Correct Answer:** D.