How is juvenile cml treated?

With targeted agents. It is rare in children, however in adults we have a new group of oral pills that can control this disease for most patients for many, many years. It is worth a discussion with the child's treating doctor concerning any data that may be available in children with these newer agents. At some point, a marrow or stem cell transplant may still be needed.
May need chemo. This now called jmml, and, unless I don't understand you correctly, you specifically excluded cml. Jmml is very rare and it affects young children. Although chemotherapy maybe used, the only curative treatment is stem cell or allogenic transplant from a compatible donor. CML is more common and affects mostly adults, but some younger patients are affected too. We treat it with drugs like gleevec (imatinib).