What condition involves a small round flat dark-red spot on the skin?

The condition characterized by a small round flat dark-red spot on the skin is indeed associated with petechiae. Petechiae are tiny punctate hemorrhages that can appear anywhere on the body, including the skin. They result from bleeding under the skin and present as small, flat, red or purple spots that do not blanch when pressed. This can occur due to various reasons, such as trauma, certain medical conditions that affect platelet function, or infections.

In contrast to petechiae, purpura typically refers to larger purple spots that can also indicate bleeding under the skin, but these are generally more extensive and can be the result of more serious conditions. Subconjunctival hemorrhage, on the other hand, is bleeding in the conjunctival membrane of the eye and does not relate to skin spots. Papilledema describes swelling of the optic disc due to increased intracranial pressure and is not associated with skin lesions at all. Thus, petechiae are the most accurate description for small round flat dark-red spots on the skin.