Final answer:
Pityriasis (tinea) versicolor is caused by the yeast genus Malassezia, leading to discolored macules on the skin, typically exacerbated by warm, humid conditions. Treatment usually consists of topical antifungal agents or systemic medication for more severe cases.
Step-by-step explanation:
Pityriasis (tinea) versicolor, a superficial skin yeast infection that leads to hypo/hyperpigmented or red macules on the skin and is often more visible after tanning, is primarily caused by the yeast of the genus Malassezia. This yeast is part of the normal skin flora but can overgrow under certain conditions, such as warm and humid environments, leading to the skin condition. This fungus affects the epidermis and generally does not spread to the underlying tissues. Treatment often involves topical antifungal creams or shampoos containing selenium sulfide, ketoconazole, or other active ingredients. In cases where the infection is more widespread or difficult to treat, systemic antifungal medication may be prescribed.