Classification of Pediatric Myeloid Malignancies RARS is rare in
children. RA and RAEB are more common. The WHO classification
schema has a subgroup that includes JMML (formerly juvenile
chronic myeloid leukemia), CMML, and Ph chromosome-negative CML.
This group can show mixed myeloproliferative and sometimes
myelodysplastic features. JMML shares some characteristics with
adult CMML [124,125,126] but is a distinct syndrome (see below).
A subgroup of children younger than 4 years at diagnosis with
myelodysplasia have monosomy 7. For this subset of children,
their disease is best classified as a subtype of JMML. The
International Prognostic Scoring System (IPSS) is used to
determine the risk of progression to AML and the outcome in
adult patients with MDS. When this system was applied to
children with MDS or JMML, only a blast count of less than 5%
and a platelet count of more than 100 x 109 /L were associated
with a better survival in MDS, and a platelet count of more than
40 x 109 /L predicted a better outcom