Which type of alopecia presents with a round patch of hair loss without inflammation?

Alopecia areata is characterized by the sudden loss of hair in well-defined, round patches, and it occurs without signs of inflammation. This autoimmune condition leads to the body's immune system mistakenly attacking hair follicles, resulting in hair falling out. The distinct pattern of round spots is a hallmark of this condition, setting it apart from other forms of hair loss.

In contrast, androgenetic alopecia involves gradual thinning of hair often related to genetics and hormonal influences, typically presenting as a diffused pattern rather than distinct patches. Telogen effluvium is a condition where hair falls out more diffusely due to stress or other factors but also does not present as isolated round patches. Traction alopecia occurs due to tension on the hair shafts, often resulting from certain hairstyles, and is characterized by hair loss along the hairlines rather than discrete patches.

The specific presentation of alopecia areata, with its round, patchy hair loss and absence of inflammation, clearly distinguishes it as the correct answer in this scenario.