DISCUSSION
Because AUL is an extremely rare disease, optimal treatment has not been established and, particularly in relapsed/refractory cases, therapy options are limited. A few B-lineage associated markers, such as CD22, are expressed in some cases of AUL.4 Weinberg et al. reported that 6 of 24 (25%) AUL cases showed partial or full CD22 co-expression,5 and in our case, CD22-positive AUL indicated a treatment strategy using InO against relapsed/refractory disease.
Use of InO increases the risk of VOD/SOS after stem cell transplantation.14 Our patient also met the proposed EBMT pediatric criteria for VOD/SOS.12 Although the severity grading was moderate (grade II) and VOD/SOS improved immediately with symptomatic therapy in this case, careful judgment should be made regarding administration of InO for AUL. Further accumulation of cases is needed to allow evaluation of the efficacy and safety of InO as a bridging therapy to stem cell transplantation in patients with CD22-positive AUL.