Pitryiasis versicolor is caused by:
## **Core Concept**
Pityriasis versicolor, also known as tinea versicolor, is a common skin condition characterized by patches of discoloration on the skin. It is caused by a yeast infection. The condition is superficial and affects the outermost layer of the skin.
## **Why the Correct Answer is Right**
The correct answer, *Malassezia*, is a type of yeast that naturally resides on human skin. Under certain conditions, such as warm and humid environments, *Malassezia* can overgrow and cause pityriasis versicolor. This yeast feeds on lipids and is lipophilic, requiring lipids for growth. The condition presents with hypo- or hyperpigmented patches, primarily on the chest and back.
## **Why Each Wrong Option is Incorrect**
- **Option A:** While certain bacteria can cause skin infections, *Staphylococcus* and *Streptococcus* are not associated with pityriasis versicolor.
- **Option B:** *Trichophyton* is a genus of fungi that causes dermatophyte infections, such as ringworm, but not pityriasis versicolor.
- **Option D:** *Candida* is a type of yeast that can cause various infections, including skin infections, but it is not the causative agent of pityriasis versicolor.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the diagnosis of pityriasis versicolor can often be made clinically, but it can be confirmed by scraping the skin and examining under a microscope, where the characteristic "spaghetti and meatballs" appearance of the yeast and hyphae can be seen. A useful clinical test is the "scotch tape test."
## **Correct Answer:** C. *Malassezia*.