The 2008 World Health Organization classification proposed a new entity in childhood
myelodysplastic syndrome, refractory
cytopenia of childhood. However, it is unclear whether this morphological classification reflects clinical outcomes. We retrospectively reviewed bone marrow morphology in 186 children (median age 8 years; range 1-16 years) who were enrolled in the prospective study and received horse
antithymocyte globulin and
cyclosporine between July 1999 and November 2008. The median follow-up period was 87 months (range 1-146 months). Out of 186 patients, 62 (33%) were classified with
aplastic anemia, 94 (49%) with refractory
cytopenia of childhood, and 34 (18%) with refractory
cytopenia with multilineage dysplasia.
Aplastic anemia patients received
granulocyte colony-stimulating factor more frequently and for longer durations than other patients (P<0.01). After six months, response rates to immunosuppressive therapy were not significantly different among the 3 groups. Acquisition of
chromosomal abnormalities was observed in 5 patients with
aplastic anemia, 4 patients with refractory
cytopenia of childhood, and 3 patients with refractory
cytopenia with multilineage dysplasia. Although the cumulative incidence of total clonal evolution at ten years was not significantly different among the 3 groups, the cumulative incidence of
monosomy 7 development was significantly higher in
aplastic anemia than in the other groups (P=0.02). Multivariate analysis revealed that only
granulocyte colony-stimulating factor administration duration of 40 days or more was a significant risk factor for
monosomy 7 development (P=0.02). These findings suggest that even the introduction of a strict morphological distinction from hypoplastic
myelodysplastic syndrome cannot eradicate clonal evolution in children with
aplastic anemia.