Key Points• Germline GATA2 mutations account for 15% of advanced and 7% of all primary pediatric MDS and do not influence overall survival. • The majority (72%) of adolescents with MDS and monosomy 7 carry an underlying GATA2 deficiency.Germline GATA2 mutations cause cellular deficiencies with high propensity for myeloid disease. We investigated 426 children and adolescents with primary myelodysplastic syndrome (MDS) and 82 cases with secondary MDS enrolled in 2 consecutive prospective studies of the European Working Group of MDS in Childhood (EWOG-MDS) conducted in Germany over a period of 15 years. Germline GATA2 mutations accounted for 15% of advanced and 7% of all primary MDS cases, but were absent in children with MDS secondary to therapy or acquired aplastic anemia. Mutation carriers were older at diagnosis and more likely to present with monosomy 7 and advanced disease compared with wild-type cases. For stratified analysis according to karyotype, 108 additional primary MDS patients registered with EWOG-MDS were studied. Overall, we identified 57 MDS patients with germline GATA2 mutations. GATA2 mutations were highly prevalent among patients with monosomy 7 (37%, all ages) reaching its peak in adolescence (72% of adolescents with monosomy 7). Unexpectedly, monocytosis was more frequent in GATA2-mutated patients. However, when adjusted for the selection bias from monosomy 7, mutational status had no effect on the hematologic phenotype. Finally, overall survival and outcome of hematopoietic stem cell transplantation (HSCT) were not influenced by mutational status. This study identifies GATA2 mutations as the most common germline defect predisposing to pediatric MDS with a very high prevalence in adolescents with monosomy 7. GATA2 mutations do not confer poor prognosis in childhood MDS. However, the high risk for progression to advanced disease must guide decision-making toward timely

A major obstacle of allogeneic haematopoietic stem cell transplantation is graft-versus-host disease, an immune-mediated disorder that affects multiple tissues and organs with varying severity. Neurological complications of acute and chronic graft-versus-host disease are rare but can produce severe clinical problems with significant morbidity and mortality. In this article, we review neurological manifestations of chronic graft-versus-host disease that comprise immune-mediated neuropathies, myasthenia gravis and myositis in the peripheral nervous system and various cerebrovascular complications, demyelination and immune-mediated encephalitis in the central nervous system. The National Institutes of Health consensus on criteria for clinical trials in chronic graft-versus-host disease recommended that the diagnosis of chronic graft-versus-host disease of the nervous system can be made only when other organs are affected by graft-versus-host disease and frequent neurological differential diagnoses such as drug-induced toxicities or opportunistic infections are excluded. The Consensus Conference on Clinical Practice in chronic graft-versus-host disease, held in autumn 2009 in Regensburg, aimed to summarize the literature and to provide guidelines for the diagnostic approach in children and adults with neurological manifestations of chronic graft-versus-host disease. Moreover, we present therapeutic recommendations and their level of evidence for the management of these complications. Overlapping symptoms and comorbidities after allogeneic haematopoietic stem cell transplantation and the limited knowledge about the underlying biological mechanisms of chronic graft-versus-host disease affecting the nervous system emphasize the need for further experimental and clinical investigations.

We analyzed 2,628 patients after allogeneic stem cell transplantation to identify risk factors and characteristics of viral encephalitis. ResultsViral encephalitis occurred in 32 patients (1.2%, 95% confidence interval 0.8%-1.6%) and was associated with the use of OKT-3 or alemtuzumab for T-cell depletion (P<0.001) and an increased mortality (P=0.011) in comparison to patients without viral encephalitis. Detected viruses included human herpesvirus-6 (28%), Epstein-Barr virus (19%), herpes simplex virus (13%), JC virus (9%), varicella zoster virus (6%), cytomegalovirus (6%) and adenovirus (3%). More than one virus was identified in 16% of the patients. The median onset time was 106 days after allogeneic stem cell transplantation for the total group of 32 patients, but onset times were shortest in those with human herpesvirus-6 encephalitis and longest in those with JC virus-associated progressive multifocal leukoencephalopathy. The probability of a sustained response to treatment was 63% (95% confidence interval 44%-82%) with a median survival of 94 (95% confidence interval 36-152) days after onset, but significant variation was found when considering different causative viruses. Patients with herpes simplex virus encephalitis had the most favorable outcome with no encephalitis-related deaths. ConclusionsThe use of OKT-3 or alemtuzumab for in vivo T-cell depletion is associated with an increased risk of viral encephalitis after allogeneic stem cell transplantation. Different viruses are frequently associated with distinct characteristics such as onset time, response to treatment and outcome.Key words: allogeneic stem cell transplantation, viral encephalitis, risk factor, treatment, outcome.Citation: Schmidt-Hieber M, Schwender J, Heinz WJ, Zabelina T, Kühl JS, Mousset S, Schüttrumpf S, Junghanss C, Silling G, Basara N, Neuburger S, Thiel E and Blau IW. Viral

Human Autosomal Recessive Osteopetrosis (ARO) is a genetically heterogeneous disorder caused by reduced bone resorption by osteoclasts. In 2000, we found that mutations in the TCIRG1 gene encoding for a subunit of the proton pump (V-ATPase) are responsible for more than one-half of ARO cases. Since then, five additional genes have been demonstrated to be involved in the pathogenesis of the disease, leaving approximately 25% of cases that could not be associated with a genotype. Very recently, a mutation in the sorting nexin 10 (SNX10) gene, whose product is suggested to interact with the proton pump, has been found in 3 consanguineous families of Palestinian origin, thus adding a new candidate gene in patients not previously classified. Here we report the identification of 9 novel mutations in this gene in 14 ARO patients from 12 unrelated families of different geographic origin. Interestingly, we define the molecular defect in three cases of ''Västerbottenian osteopetrosis,'' named for the Swedish Province where a higher incidence of the disease has been reported. In our cohort of more than 310 patients from all over the world, SNX10-dependent ARO constitutes 4% of the cases, with a frequency comparable to the receptor activator of NF-kB ligand (RANKL), receptor activator of NF-kB (RANK) and osteopetrosisassociated transmembrane protein 1 (OSTM1)-dependent subsets. Although the clinical presentation is relatively variable in severity, bone seems to be the only affected tissue and the defect can be almost completely rescued by hematopoietic stem cell transplantation (HSCT). These results confirm the involvement of the SNX10 gene in human ARO and identify a new subset with a relatively favorable prognosis as compared to TCIRG1-dependent cases. Further analyses will help to better understand the role of SNX10 in osteoclast physiology and verify whether this protein might be considered a new target for selective antiresorptive therapies. ß

our data confirm that haematopoietic stem cell transplantation can stop the progress of demyelination when performed at a critical early stage of the disease. The prognosis in an individual patient for the clinical course after stem cell transplantation can in general be given based on the status before transplantation, although individual patients may show an unexpected course.