Molecular characterization of six new cases of red blood cell hexokinase deficiency yields four novel mutations in HK1.

Hexokinase (HK) is a key enzyme of glycolysis, the only metabolic pathway able to provide the red blood cell with ATP. HK deficiency is a very rare hereditary disorder with severe chronic nonspherocytic hemolytic anemia (HNSHA) as a major clinical feature. To date, only 24 patients with HK deficiency have been identified. Here, we report the molecular analysis of six new cases of HK deficiency. A total of six different mutations were detected in HK1, four of them described here for the first time: c.2599C>T p.(His867Tyr), c.1799C>T p.(Thr600Met), c.873-2A>G and c.493-1G>A. The pathogenic nature of the identified missense mutations was confirmed by biochemical and 3-dimensional structural analysis. The effects of the novel splice site mutation c.873-2A>G were studied at the level of pre-mRNA processing, and confirmed at the protein level. All together, these results provide a better insight into the pathogenesis of this rare red cell disorder, and contribute to a better understanding of the genotype-phenotype correlation in HK deficiency.

Loss of B cells and their precursors is the most constant feature of GATA-2 deficiency in childhood myelodysplastic syndrome.

GATA-2 deficiency was recently described as common cause of overlapping syndromes of immunodeficiency, lymphedema, familiar myelodysplastic syndrome or acute myeloid leukemia. The aim of our study was to analyze bone marrow and peripheral blood samples of children with myelodysplastic syndrome or aplastic anemia to define prevalence of the GATA2 mutation and to assess whether mutations in GATA-2 transcription factor exhibit specific immunophenotypic features. The prevalence of a GATA2 mutation in a consecutively diagnosed cohort of children was 14% in advanced forms of myelodysplastic syndrome (refractory anemia with excess blasts, refractory anemia with excess blasts in transformation, and myelodysplasia-related acute myeloid leukemia), 17% in refractory cytopenia of childhood, and 0% in aplastic anemia. In GATA-2-deficient cases, we found the most profound B-cell lymphopenia, including its progenitors in blood and bone marrow, which correlated with significantly diminished intronRSS-Kde recombination excision circles in comparison to other myelodysplastic syndrome/aplastic anemia cases. The other typical features of GATA-2 deficiency (monocytopenia and natural killer cell lymphopenia) were less discriminative. In conclusion, we suggest screening for GATA2 mutations in pediatric myelodysplastic syndrome, preferentially in patients with impaired B-cell homeostasis in bone marrow and peripheral blood (low number of progenitors, intronRSS-Kde recombination excision circles and naïve cells).

Venous thromboembolism in adolescents.

The incidence of venous thromboembolism (VTE) during childhood is low with two peaks - neonatal and adolescent age. This retrospective study is focused on clinical characteristics ofVTE during adolescence. The main goals are to assess the most frequent inherited and acquired risk factors and to evaluate the benefit of D-dimers in diagnostics of venous thromboemblism. The data of 18 adolescents were analysed--16 girls (88.9%), 2 boys (11.1%). In 9 patients (50%) thrombosis of the lower limb deep veins was diagnosed, six patients (33.3%) suffered from symptomatic pulmonary embolism (PE) and 3 patients (16.7%) from thrombosis at unusual sites. One patient had an idiopathic VTE, the mean number of the inherited and acquired risk factors was 2.6. The most frequent inherited risk factor was Leiden mutation of factor V (27.8%). The most frequent acquired risk factor was oral contraception (OC) in 12 out of 16 girls (75%). All of our patients on oral contraception had one or more additional risk factors. 10 out of 18 (55.6%) patients with VTE had elevated activity of factor VIII. The sensitivity of D-dimers was low (50%) in patients with distal lower limb thrombosis, but very high (100%) in patients with PE.