For a journal that is Q1/Q2 specifically about this topic... there are a few for adults but not so much for pediatric... There are also some which do not specify adult or pediatric.
There are also some in Q3/Q4...
Would you consider those...?
The only one I have found so far is a journal called "Pediatric Blood and Cancer".
My other suggestions would be journals in pediatrics that takes case reports or in hematology.
Case Reports & Case Series. Reports of special cases that contribute to a better understanding of hematological diseases or to patient care will be considered for publication. These reports need to be conclusive and must include pathogenetic insights in addition to the description of the clinical case(s). Only few Case Reports can be published and a strict selection is in place. Case Reports have no abstract, no headings, and a maximum of 1,500 words in the text (excluding tables, figure legends and references), a maximum of three tables and/or figures, and 15 references. Supplementary data can't be used.