Okay, maybe defect wouldn't be the right word. Anomaly, perhaps?
On a similar note, I'm also curious about what boon or drawback this things give these people. For example, extra fingers can allow for better dexterity and grip
I also found a Tumblr post that looked at various deformities and brought up a certain fictional race, and explored how those same deformities, while detrimental humans, would be useful to this other race.
I wish I could find it again