Abstract • 28

Within EWOG-MDS we have collected data on 177 children with JMML. Median age at diagnosis was 2.0 years, median white blood count (WBC) 33. 3×109 /L (range 3.1-259.4). Forty-five children were known to have a monosomy 7, 15 had other chromosomal aberrations. Children with monosomy 7 had a significantly lower WBC than children with normal karyotype (20.4×10109/L versus 39.1×10109/L). In addition, JMML with monosomy 7 was characterized by presence of eosinophilia in the bone marrow and macrocytic anemia with normal or only slightly elevated hemoglobin F. In the past some investigators had classified young children with monosomy 7 and any FAB type as monosomy 7 syndrome. The monosomy 7 syndrome was regarded as myeloproliferative disease while JMML with normal karyotype is often considered a myelodysplastic disease, although JMML with monosomy 7 generally displays less myeloproliferative features than JMML with normal karyotype. We will describe the clinical and hematological characteristics of patients with JMML and primarily dysplastic or proliferative features.