{'fraction_non_alphanumeric': 0.03235515425131678, 'fraction_numerical': 0.009405568096313018, 'mean_word_length': 4.975280898876404, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
ABO incompatibility and bone marrow transplantation in children with thalassemia major

To the Editor, We read with interest the article on ABO mismatch in children with thalassemia major (1). There is paucity of data on impact of ABO incompatibility in pediatric thalassemia transplants, and we will like to share our experience. During the last one year, 12 children (seven males and five females) with transfusiondependent beta thalassemia major underwent a peripheral blood stem cell transplant (PBSCT) at our center. Median age was seven yr (range 2–16 yr). All children had a fully HLA identical sibling donor and received myeloablative conditioning with busulfan, cyclophosphamide, and antithymocyte globulin (2). ABO incompatibility was defined as discussed previously (1). Five patients were ABO incompatible (3 major and 2 minor). One child each developed veno-occlusive disease (VOD) of liver and grade 2 skin graft versus host disease (GVHD) (Table 1). Median follow-up was seven months (6– 9.5 months). There was no 100-day mortality. There was no chronic GVHD in our short follow-up. All patients are surviving without thalassemia at last follow-up. Table 1 summarizes the clinical data. It is apparent that two groups received identical peripheral blood stem cell doses. There was no difference in neutrophil engraftment between ABO compatible and incompatible groups. There was a trend toward delayed erythroid engraftment and thereby increased transfusion requirement in ABO incompatible group. This did not reach statistical significance. There are a few distinguishing points about our small data. First, all children received peripheral blood stem cell transplantation (PBSCT). We did not find any significant difference in erythroid engraftment rates and packed red blood cell (PRBC) transfusions between two subgroups. We had small incidence of VOD and acute GVHD to draw any meaningful conclusions. Booth et al. in their review have shown lack of importance of ABO incompatibility in overall bone marrow transplantation (BMT) survival (3). Data on pediatrics, however, are scarce (4). Atay et al. in their detailed analysis found lack of significance of ABO incompatibility in incidence of VOD, GVHD, and general outcome of BMT (1). Due to smaller numbers and shorter follow-up, it is difficult to comment on the incidence of chronic GVHD. It is possible that during longer follow-up, some of the variables like chronic GVHD may change. We surprisingly have all the children surviving without thalassemia and without 100-day mortality. It is possible that the use of PBSCT instead of bone marrow as stem cell source helped our patients