What condition is characterized by red patches on the skin that may be round or oval?

Pityriasis rosea is a skin condition often recognized by the appearance of red, oval, or round patches on the skin. These patches can be slightly scaly and are typically accompanied by a herald patch, which is larger and may precede the smaller patches that appear in a Christmas tree pattern on the back. The condition is usually benign and self-limiting, often resolving within several weeks to a couple of months without the need for treatment.

The other options do not fit the description as accurately. Scleroderma primarily affects deeper layers of the skin and typically results in thickening and hardening of the skin rather than the distinct red patches seen in pityriasis rosea. Plasma, while commonly referenced in medical contexts, does not describe a specific skin condition characterized by such patches. Telangiectasia refers to small, visible blood vessels on the skin, which do not form the round or oval skin patches described in the question. Therefore, pityriasis rosea is the most fitting answer.