Reduced-intensity conditioning (RIC) for pediatric patients is expected to reduce both acute and late treatment-related complications after hematopoietic transplant. In our study, the RIC group developed fewer late effects than the MAC group, although the follow-up period was short. For pediatric patients for whom long-term survival is expected, RIC may be a feasible and useful option to reduce late effects. Long-term follow-up is important to detect late effects and perform appropriate interventions. It is important to inform patients and their families about late complications, and organ functions should be preserved as much as possible.

 We describe the case of a 2-year-old girl with a primary left upper mediastinal neuroblastoma with bone metastasis. She underwent autologous peripheral blood stem cell transplantation following chemotherapy with high-dose busulfan-melphalan. On day 61, she developed pulmonary hypertension with generalized fatigue and hypoxemia. On day 91, she was diagnosed with transplant-associated thrombotic microangiopathy (TA-TMA) secondary to anemia, red cell fragmentation, thrombocytopenia, and elevated serum creatinine levels, and her pulmonary hypertension worsened. She underwent cardiac catheterization and was diagnosed with pulmonary arterial hypertension (PAH). Management of fluid balance led to improvement in TA-TMA, and oxygen therapy was initiated for PAH. On day 131, she developed cardiac arrest secondary to pulmonary hypertensive crisis. Although she was successfully treated with multidisciplinary therapy, she had neurological sequelae. PAH improved following treatment with sildenafil and bosentan. PAH and TA-TMA are serious complications that may occur owing to vascular endothelial damage after hematopoietic stem cell transplantation. Clinicians must be vigilant for TA-TMA in patients who develop PAH after hematopoietic stem cell transplantation.

 Acute myelogenous leukemia (AML) with t (16;21) (p11;q22) is a rare leukemia subtype with a relatively high incidence in young individuals and a poor prognosis. This chromosomal rearrangement results in FUS-ERG fusion transcripts. We describe a patient with AML with t (16;21) (p11;q22) who underwent successful monitoring for FUS-ERG fusion transcripts by real-time quantitative polymerase chain reaction (RT-qPCR). We designed DNA primers based on the leukemic cells of this patient and monitored minimal residual disease by RT-qPCR. Standard multiagent chemotherapy for AML could not reduce FUS-ERG expression level to 10³, whereas hematopoietic stem cell transplantation (HSCT) knocked down the expression level to 10 or lower. The patient underwent HSCT twice, and FUS-ERG expression decreased rapidly, especially after human leukocyte antigen (HLA)-haploidentical HSCT. Although the patient suffered multiple early recurrences after HSCTs, this case suggests that HLA-haploidentical HSCT is one of the options for AML with t (16;21) (p11;q22), even though the benefits are limited. Further research is needed to optimize the course of treatment including pre-transplant treatment, HSCT, and post-transplant treatment strategies (Trial registration: jRCTs051180119).