A 24 year old male came with hypopigmented skin lesions over his trunk with fine, powdery scales which becomes prominent on scratching the skin. KOH mount of the lesions shows
**Core Concept**
**Pityriasis versicolor is a superficial fungal infection caused by Malassezia species.** This condition is characterized by hypopigmented skin lesions with fine scales, often exacerbated by scratching. The KOH mount is a diagnostic tool used to identify the causative organism.
**Why the Correct Answer is Right**
The correct answer is based on the presence of **Malassezia yeast** in the KOH mount. Malassezia species are naturally occurring lipophilic yeasts that colonize the skin, particularly in areas rich in sebaceous glands. In individuals with impaired immune function or altered skin pH, these yeasts can proliferate and cause pityriasis versicolor. The fine, powdery scales are a result of the yeast's ability to break down keratin and sebum.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the causative organism, and the presence of other fungal species would not explain the characteristic fine scales and hypopigmentation.
**Option B:** This option is incorrect because it refers to a different condition altogether, which is characterized by erythematous plaques and not fine scales.
**Option C:** This option is incorrect because it mentions a bacterial infection, which is not consistent with the KOH mount findings.
**Clinical Pearl / High-Yield Fact**
**Malassezia species are lipophilic yeasts that thrive in areas rich in sebaceous glands, making them more likely to cause pityriasis versicolor in individuals with oily skin or acne.**
**Correct Answer:** D. **Malassezia**