Clinical characteristics and genetic analysis of childhood acute lymphoblastic leukemia with hemophagocytic lymphohistiocytosis: a Japanese retrospective study by the Kyushu-Yamaguchi Children's Cancer Study Group.

This present study sought to analyze acute lymphoblastic leukemia (ALL) patients with hemophagocytic lymphohistiocytosis (HLH) registered in Kyushu-Yamaguchi Children's Cancer Study Group studies conducted between 1996 and 2007. Four of 357 patients, including two of 318 patients with B cell precursor acute lymphoblastic leukemia (BCP-ALL) and two of 39 of those with T cell acute lymphoblastic leukemia (T-ALL), were identified. HLH was observed more frequently in the T-ALL patients than in the BCP-ALL patients (P = 0.061). The mean age of 13.0 years at the diagnosis of leukemia in the HLH + ALL group was significantly higher than the 6.05 years observed in the remaining ALL groups (P = 0.001). A female predisposition was noted, as all four patients were female (P = 0.043). In two of four patients, the leukemic cells exhibited deletions on the long arm of chromosome 6 (P = 0.003). Three patients suffered from HLH during maintenance therapy. Parvovirus B19 infection and cytomegalovirus reactivation were identified as causes of HLH in one and two patients, respectively. All four patients are currently in complete remission, although one developed relapse of leukemia after receiving maintenance therapy. Based on the genetic analyses, non-synonymous single nucleotide polymorphisms (SNPs) in UNC13D, syntaxin 11, and STXBP2 were identified in all patients. Clinicians should therefore be aware of the risk of HLH during maintenance therapy, especially in older T-ALL patients with SNPs in familial HLH causative genes.