Aengus O'Marcaigh

Nf1 and Gmcsf Interact in Myeloid Leukemogenesis

The NF1 tumor suppressor gene encodes neurofibromin, a GTPase-activating protein (GAP) for p21ras (Ras). Children with NF1 are predisposed to juvenile myelomonocytic leukemia (JMML). Some heterozygous Nf1 mutant mice develop a similar myeloproliferative disorder (MPD), and adoptive transfer of Nf1-deficient fetal liver cells consistently induces this MPD. Human JMML and murine Nf1-deficient cells are hypersensitive to granulocyte-macrophage colony-stimulating factor (GM-CSF) in methylcellulose cultures. We generated hematopoietic cells deficient in both Nf1 and Gmcsf to test whether GM-CSF is required to drive excessive proliferation of Nf1-/- cells in vivo. Here we show that GM-CSF play a central role in establishing and maintaining the MPD and that recipients engrafted with Nf1-/- Gmcsf-/- hematopoietic cells are hypersensitive to exogenous GM-CSF.

Stomatocytic haemolysis and macrothrombocytopenia (Mediterranean stomatocytosis/macrothrombocytopenia) is the haematological presentation of phytosterolaemia

Phytosterolaemia (sitosterolaemia) is a recessively inherited metabolic condition in which the absorption of both cholesterol and plant‐derived cholesterol‐like molecules at the gut is unselective and unrestricted. In haematology, Mediterranean stomatocytosis or Mediterranean macrothrombocytopenia is a poorly understood haematological condition that combines stomatocytic haemolysis with the presence of very large platelets. Five pedigrees showing this haematology were identified. Gas chromatography mass spectrometry (GC‐MS) showed that all of the patients with this highly specific haematology had grossly elevated levels of phytosterols in the blood, diagnostic of phytosterolaemia. All showed mutations in the ABCG5 and ABCG8 previously linked to phytosterolaemia. Three pedigrees showed five new mutations, while two pedigrees showed the common W361X mutation in ABCG8. We draw the following four conclusions: (i) that Mediterranean stomatocytosis/macrothrombocytopenia is caused by an excess of phytosterols in the blood; (ii) that phytosterolaemia, which does not respond to standard statin treatment, can be diagnosed via the distinctive haematology described here, even when the cholesterol is normal; (iii) that phytosterolaemia should be considered in the differential diagnosis of all patients with large platelets; and (iv) that the platelet size should be noted in patients with hypercholesterolaemia.

Treatment for myeloid leukaemia of Down syndrome: population-based experience in the UK and results from the Medical Research Council AML 10 and AML 12 trials

Down syndrome (DS) children are at an increased risk of developing myelodysplasia and acute myeloid leukaemia (AML). We retrospectively analysed the population‐based data on 81 children with myeloid leukaemia of Down syndrome (ML‐DS) from the UK National Registry of Childhood Tumours and experience in the Medical Research Council (MRC) AML 10 and AML 12 trials, which enrolled 46 children with ML‐DS from 1988 to 2002. Eight per cent of UK children with AML had DS, but DS children comprised only 5% of children registered in MRC trials. The unique clinical characteristics of ML‐DS were confirmed. Overall survival (OS) of ML‐DS at 5 years increased from 47% in UK children diagnosed from 1988 to 1995 to 75% in children diagnosed from 1996 to 2002. OS for DS children registered in AML 10 and AML 12 was 74% in 5 years and improved from AML 10 to AML 12 (56% vs. 83%) There was no significant difference in OS between DS and non‐DS children (OS: 74% vs. 62%, P = 0·4) in the trials, but this result masked a significant increase in early death amongst DS children, with a significant reduction in mortality later on. Relapse was significantly reduced (3% vs. 39%, P = 0·0003), leading to the improved disease‐free survival (83% vs. 56%, P = 0·02). Given the increased number of earl treatment‐related deaths, future treatment protocols should aim to reduce chemotherapy dosage or intensity whilst maintaining low rates of resistant and recurrent disease.

Bone marrow transplantation for T − B − severe combined immunodeficiency disease in Athabascan-speaking native Americans

A distinct form of autosomal recessive T−B− severe combined immunodeficiency disease occurs with a high frequency among Athabascan-speaking Native Americans (SCIDA), including Navajo and Apache Indians from the southwestern US and Dene Indians from the Canadian Northwest Territories. The SCIDA gene has been linked to markers on chromosome 10p although its identity and role in the pathogenesis of this disease are unknown. We report our experience in treating 18 Navajo and Dene children with SCIDA between 1984 and 1999; 16 underwent bone marrow transplants (BMT). All children were symptomatic within 2 months of birth, had the T−B−NK+SCID phenotype and 67% presented with oral and/or genital ulcers. Three children had evidence of maternal engraftment prior to transplant. Two children died shortly after diagnosis. Three children required more than one BMT and 12 are alive with T cell reconstitution at a median follow-up of 7 years. Three children developed normal B cell immunity, two of whom received ablative conditioning therapy with either radiation or busulfan. Three of the four children who died received therapy with either radiation or busulfan and two of eight long-term survivors who were also recipients of cytotoxic chemotherapy have failed to develop secondary teeth. These results demonstrate the efficacy of BMT in treating infants with this distinct form of SCID, although B cell reconstitution remains a problem even with HLA-matched donors. Without conditioning, T cell engraftment is likely when closely HLA-matched donors are used. With T cell depletion of haplocompatible marrow, conditioning with immunosuppressive therapy may be necessary; however, children with SCIDA who were treated with intensive immunosuppressive and myeloablative therapy had a poor outcome. Bone Marrow Transplantation (2001) 27, 703–709.

Hematopoietic stem cell transplantation for advanced myelodysplastic syndrome in children: results of the EWOG-MDS 98 study

We report on the outcome of children with advanced primary myelodysplastic syndrome (MDS) transplanted from an HLA-matched sibling (MSD) or an unrelated donor (UD) following a preparative regimen with busulfan, cyclophosphamide and melphalan. Ninety-seven patients with refractory anemia with excess blasts (RAEB, n=53), RAEB in transformation (RAEB-T, n=29) and myelodysplasia-related acute myeloid leukemia (MDR-AML, n=15) enrolled in the European Working Group of MDS in Childhood (EWOG-MDS) 98 study and given hematopoietic stem cell transplantation (HSCT) were analyzed. Median age at HSCT was 11.1 years (range 1.4–19.0). Thirty-nine children were transplanted from an MSD, whereas 58 were given the allograft from a UD (n=57) or alternative family donor (n=1). Stem cell source was bone marrow (n=69) or peripheral blood (n=28). With a median follow-up of 3.9 years (range 0.1–10.9), the 5-year probability of overall survival is 63%, while the 5-year cumulative incidence of transplantation-related mortality (TRM) and relapse is 21% each. Age at HSCT greater than 12 years, interval between diagnosis and HSCT longer than 4 months, and occurrence of acute or extensive chronic graft-versus-host disease were associated with increased TRM. The risk of relapse increased with more advanced disease. This study indicates that HSCT following a myeloablative preparative regimen offers a high probability of survival for children with advanced MDS.

Myeloid leukemia in children 4 years or older with Down syndrome often lacks GATA1 mutation and cytogenetics and risk of relapse are more akin to sporadic AML.

Myeloid leukemia in children 4 years or older with Down syndrome often lacks GATA1 mutation and cytogenetics and risk of relapse are more akin to sporadic AML

Potentiation of vincristine toxicity by itraconazole in children with lymphoid malignancies

Eight consecutive paediatric patients with acute lymphoblastic leukaemia (ALL) (n=7) and T‐cell non‐Hodgkins lymphoma (NHL) (n=1) presenting within a 5‐wk interval were started on a standard induction protocol which included weekly treatment with vincristine for 4 wk. Itraconazole was commenced as antifungal prophylaxis, 1–21 d after the first injection of vincristine. Within 2 to 4 wk, enhanced vincristine neurotoxicity was noted in all patients, abdominal cramps and constipation occurred most frequently, and one patient developed a bowel perforation associated with paralytic ileus. Hyponatraemia associated with SIADH was observed in three patients and four patients developed seizures. An additional patient with B cell NHL developed seizures 5 d after an injection of vincristine. Recovery was complete in all patients and ranged from 2 d to 15 wk.

Does isochromosome 7q mandate bone marrow transplant in children with Shwachman–Diamond syndrome?

Summary. We report on nine children with Shwachman–Diamond syndrome (SDS), eight of whom had clonal abnormalities of chromosome 7. Seven children had an isochromosome 7 [i(7)(q10)] and one a derivative chromosome 7, all with an apparently identical (centromeric) breakpoint. Children with SDS are predisposed to myelodysplasia (MDS) and acute myeloid leukaemia (AML) often with chromosome 7 abnormalities. Allogeneic transplants have been used to treat these children, however, they are a high‐risk transplant group and require careful evaluation. Three of the children were transplanted but only one survived, who to our knowledge remains the longest surviving SDS transplant patient (4·5 years +). The six non‐transplanted children are well. In classic MDS, chromosome 7 abnormalities are associated with rapid progression to acute leukaemia; however, we present evidence to suggest that isochromosome 7q may represent a separate disease entity in SDS children. This is a particularly interesting finding given that the SDS gene has recently been mapped to the centromeric region of chromosome 7. Our studies indicate that i(7)(q10) is a relatively benign rearrangement and that it is not advisable to offer allogeneic transplants to SDS children with i(7)(q10) alone in the absence of other clinical signs of disease progression.

Second allogeneic hematopoietic stem cell transplantation (HSCT) results in outcome similar to that of first HSCT for patients with juvenile myelomonocytic leukemia

Second allogeneic hematopoietic stem cell transplantation (HSCT) results in outcome similar to that of first HSCT for patients with juvenile myelomonocytic leukemia

Successful Treatment of Intrathecal Methotrexate Overdose by Using Ventriculolumbar Perfusion and Intrathecal Instillation of Carboxypeptidase G2

Prompt and appropriate management measures are critical in order to achieve a favorable outcome after a major overdose of intrathecally (IT) administered methotrexate (MTX). Published information available to guide clinicians in the immediate management of this medical emergency is scant. Herein we describe a 6-year-old boy with acute lymphoblastic leukemia who received an inadvertent overdose of 600 mg of IT administered MTX instead of the intended dose of 12 mg. Severe acute neurotoxicity developed rapidly. Lumbar puncture and drainage of 15 mL of cerebrospinal fluid 2 hours after administration resulted in removal of 32% of the administered drug. Ventriculolumbar perfusion with 240 mL of warmed isotonic saline through ventricular and lumbar catheters for 3 hours resulted in removal of a total of 90% of the drug within 8 1/2 hours after administration. IT administration of 2,000 U of carboxypeptidase G2 (CPDG2), an enzyme that inactivates MTX, resulted in a further 150-fold reduction in cerebrospinal fluid MTX concentration. The patient experienced complete recovery. To our knowledge, this is the first reported case of the use of IT instillation of CPDG2 for the treatment of an overdose of IT administered MTX in a human, and it is only the second reported favorable outcome after an IT overdose of more than 500 mg of MTX. Minor IT overdoses of MTX can be managed by immediate lumbar drainage alone. Major overdoses may also necessitate prompt ventriculolumbar perfusion, IT instillation of CPDG2, and further supportive measures for a successful outcome after this infrequent but potentially catastrophic event.