Program: Oral and Poster Abstracts
Session: 508. Bone Marrow Failure: Poster I
The Japanese Society of Pediatric Hematology and Oncology has established a central review system of morphology. Peripheral blood (PB) and BM smears were reviewed by two pediatric hematologists, and BM trephine biopsies were reviewed by a hematopathologist. In addition, the telomere length of lymphocytes and paroxysmal nocturnal hemoglobinuria (PNH) clones in PB were measured by flowcytometry. RCC is defined as persistent cytopenia with <2% and <5% blasts in PB and BM, respectively. BM aspirate smears show dysplastic changes in >2 cell lineages or >10% within one cell lineage. On the other hand, the criteria of RCMD is defined as persistent cytopenia with <1% and <5% blasts in PB and BM, respectively. BM smears show >10% dysplastic changes in >2 cell lineages. We classified childhood BMF into AA, RCC, and RCMD in our central review.
From February 2009 to February 2015, 1,300 cases were prospectively reviewed. Of the 1,300 cases, 582 were classified as BMF. Among them, 99 were classified as AA, 230 as RCC, 128 as RCMD, 50 as hepatitis-related BMF, 4 as PNH, and 71 as inherited BMF. Of the 71 cases with inherited BMF, 35 were diagnosed as Fanconi anemia, 14 as Shwachman–Diamond syndrome, and 12 as dyskeratosis congenita. To determine the clinical differences among AA, RCC, and RCMD, we compared laboratory and clinical findings for 457 patients classified with AA, RCC, and RCMD. Median ages in the AA, RCC, and RCMD groups were 10, 9, and 7 years, respectively (p<0.01). The male/female ratio in AA, RCC, and RCMD groups was 1.3, 1.4, and 1.1. The median of leukocyte, neutrophil, reticulocyte, and platelet count, and mean corpuscular volume were significantly lower in AA than in RCC and RCMD groups (p<0.01). Chromosomal abnormalities were detected in 1 patient with AA (trisomy 8), 6 patients with RCC (trisomy 8, n=4; monosomy 7, n=1; other, n=1), and 18 patients with RCMD (trisomy 8, n=5; monosomy 7, n=4; other, n=9) (p<0.01). Out of the 457 patients, 69 (AA, n=29; RCC, n=34; RCMD, n=6) were treated with immunosuppressive therapy (IST) with rabbit antithymocyte globulin and cyclosporine. Six months after the IST, the response rate to the IST was not significantly different between AA (38%) and RCC (47%) (p=0.47). Although the number of patients was limited, the response rate to the IST was 100% in patients with RCMD. One patient with RCC developed PNH at 26 months after the IST. Stem cell transplantation was performed in 15 patients with AA, 16 with RCC, and 3 with RCMD. Two patients with AA and 1 patient with RCC died of transplant-related toxicities.
In conclusion, the entity of RCMD should be adopted to childhood MDS classification because children with RCMD exhibited a distinct characteristic of morphology and laboratory findings. Further efforts to clarify molecular events and clinical outcomes are necessary to establish the classification system for childhood BMF.
Disclosures: No relevant conflicts of interest to declare.
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