Coexistence of treatment-related MLL cleavage and rearrangement in a child with haemophagocytic lymphohistiocytosis

Acute myeloid leukemia following etoposide therapy for EBV-associated hemophagocytic lymphohistiocytosis: a case report and a brief review of the literature

Background

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening disorder characterized by prolonged fever, cytopenia, hepatosplenomegaly, rash, icterus, and other neurological symptoms. Successful treatment of HLH by etoposide has improved outcomes for children with HLH. However, the development of treatment-related acute myeloid leukemia (t-AML) after the usage of this drug is a concern.

Case presentation

We report a case of acquired EBV-triggered HLH with progression to t-AML following etoposide therapy with cytogenetic abnormality for t (11; 19) (q23; p13) resulting in MLL gene fusion. The development of t-AML was detected 23 months after HLH diagnosis.

Conclusions

Although the successful treatment of HLH by etoposide has improved outcomes for children with HLH, t-AML is a serious complication of topoisomerase II inhibitor therapy and is characterized by the presence of gene rearrangement. This study suggests that HLH patients undergoing therapy with HLH-2004 protocol need monitoring for future malignancy, especially in the initial 2 to 3 years.

Covert preleukemia driven by MLL gene fusion

Acute leukemia is considered to be a two- or multiple-step process. Although there is a considerable knowledge regarding the character of the "first hit," the nature of the "second hit" remains unanswered in most of the cases including leukemias with MLL gene rearrangement. We demonstrate here a striking sequence of events, which include a covert, protracted preleukemic phase characterized by a dominant MLL/FOXO3A clone with intact myeloid differentiation and the subsequent acquisition of a secondary genetic abnormality, leading to overt lymphoblastic leukemia. Backtracking of the secondary acute lymphoblastic leukemia (sALL) with the MLL rearrangement showed no blasts in the bone marrow (BM) during the protracted preleukemic phase. However, at the same time (more than 1 year before the sALL diagnosis) the MLL/FOXO3A was present in up to 90% of BM cells including myeloid lineage, suggesting that the fusion arose in a multipotent progenitor. To identify potential "second hit" precipitating sALL we compared DNA in preleukemic versus fully leukemic samples. The analysis revealed a 10 Mb gain on 19q13.32 in the sALL, absent in the preleukemic specimen. These data provide insight into the dynamics of leukemogenesis in secondary leukemia with MLL rearrangement.

Spectrum and clinical implications of syntaxin 11 gene mutations in familial haemophagocytic lymphohistiocytosis: association with disease-free remissions and haematopoietic malignancies

OBJECTIVE

To determine the frequency and spectrum of mutations in the gene encoding syntaxin 11 (STX11) in familial haemophagocytic lymphohistiocytosis (FHL), a rare autosomal recessive disorder of immune dysregulation characterised by a defect in natural killer cell function.

METHODS

Mutational analysis of STX11 by direct sequencing was done in 28 FHL families that did not harbour perforin mutations, previously identified in some FHL patients. A detailed investigation of clinical features of these patients was also undertaken.

RESULTS

Two different STX11 mutations were identified, one nonsense mutation and one deletion, affecting six of 34 children in four of 28 unrelated PRF1 negative families. Both mutations have been reported before. Three patients experienced long periods (> or = 1 year) in remission without specific treatment, which is very uncommon in this disease. Despite the milder phenotype, some children with STX11 mutations developed severe psychomotor retardation. Two of the six patients harbouring STX11 gene defects developed myelodysplastic syndrome (MDS) or acute myelogenous leukaemia (AML).

CONCLUSIONS

STX11 gene mutations were found in 14% of the PRF1 negative FHL families included in the present cohort. These results suggest that STX11 gene mutations may be associated with secondary malignancies (MDS/AML), and that there is segregation of specific clinical features in FHL patients with an underlying genotype.