Mystery injury on cat leg

I just got a couple new older kittens from a rescue organization I foster for. They've been with another foster for a while, but her cats were picking on the kittens, so she had to confine them to the bathroom when the family was at work during the day and it just wasn't working out, and they asked me to take them. I noticed a bald patch on the foreleg of the tabby, the previous foster mom didn't have any idea what it was, but so far the cat has been sneezing, and also appears to have ear mites, so I don't think she was paying a lot of attention to them. It's about the size of a nickel, is red and and a little crusty, but doesn't appear to be infected. I won't be taking him to the vet unless the organization asks me to, but I was wondering if anyone had seen something similar. It almost looks like a burn.

Whatever it is, you should get them to the vet ASAP to have it checked out.  It could be almost anything and you don't want it to get worse.

To clarify, I have already starting treating him with antibiotics for a URI, and I will be receiving medication for the ear mites and some ointment for the leg in the mail today, so it's not a matter of the cat not receiving any care. It is not a life-threatening injury. My inquiry here is merely to see if anyone else had experienced something similar to it.

looks like a trauma, possibly done by himself if not anything else- especially if he was in a stressful environment. I could be wrong though.

Did you ask the previous foster if any of her cats have something similar? Is the other kitten okay? My first thought was ringworm, but it doesn't look quite right for that. Some cats will overgroom when they're stressed. That can lead to bald spots and sores because their little tongues are so rough.

I hope the antibiotics and ointment help. If you don't see improvement within a day or two I would ask the organization if you can take him to the vet. Antibiotics won't help if it's a fungal infection (ringworm or something related).

They're older kittens, about six months old now. The previous foster didn't notice the bald spot, or the ear mites or the sneezing, so she wasn't a lot of help. He was at the home with his brother, who doesn't have any similar symptoms, but they were being picked on by the foster's older cats, so it could be stress related. I haven't seen him licking or bothering with it since he's been with me. It really looks like it's in the stages of healing, but it will probably take a while for the fur to grow back.

After he's over his URI, I'll be taking them to the Humane Society to get their rabies shots. They provide the spay/neuter services and reduced vaccination costs for the rescue organization. Even though they don't provide full service veterinary services, I can probably ask the vet about it then if it doesn't seem to be improving.

Maybe he was sticking his paw under the bathroom door at the other fosters house and rubbed it on the bottom of the door. I have a younger cat who does that when a doors closed.