Like adults, a child's OCD symptoms will differ from person to person, but they all generally have the same idea. I've had OCD for as long as I can remember, and it's always been health related. I'm a full blown hypochondriac and even when I was tiny, I would freak out over small things relating to my body and my health.
When I was about 5 years old, I was eating and some food got caught in my throat. It eventually went down and I was okay. I didn't choke or lose air or anything, but it definitely freaked me out. It scared me so badly that I didn't eat for months. I lost so much weight. I got incredibly skinny. I only ate noodles, because they could be swallowed easily and with little worry. My mom was pretty concerned about this and took me to my first therapist. The doctor didn't know what the hell she was doing or talking about, and said that I had ADHD. I didn't even express symptoms of that. I just don't think she understood anxiety and OCD.
Anyway, it's only gotten worse since then, and I've been properly diagnosed with OCD for roughly five years. I'm not sure what my point is, but I guess I'm just trying to say that children can definitely show signs of obsessive-compulsive disorder. Maybe if a child is constantly organizing, washing, counting, worrying, ect., those may be signals that something could be wrong?