Genotype/phenotype correlations of childhood-onset congenital sideroblastic anaemia in a European cohort.

Congenital sideroblastic anaemia (CSA) is a rare disease caused by germline mutations of genes involved in haem and iron-sulphur cluster formation, and mitochondrial protein biosynthesis. We performed a retrospective multicentre European study of a cohort of childhood-onset CSA patients to explore genotype/phenotype correlations. We studied 23 females and 20 males with symptoms of CSA. Among the patients, the most frequently mutated genes were ALAS2 (n = 10; 23·3%) and SLC25A38 (n = 8; 18·6%), causing isolated forms of microcytic anaemia of varying severity. Five patients with SLC19A2 mutations suffered from thiamine-responsive megaloblastic anaemia and three exhibited the 'anaemia, deafness and diabetes' triad. Three patients with TRNT1 mutations exhibited severe early onset microcytic anaemia associated with thrombocytosis, and two exhibited B-cell immunodeficiency, inflammatory syndrome and psychomotor delay. The prognoses of patients with TRNT1 and SLC2A38 mutations were generally dismal because of comorbidities or severe iron overload. No molecular diagnosis could be established in 14/43 cases. This study emphasizes the frequency of ALAS2 and SLC25A38 mutations and provides the largest comprehensive analysis to date of genotype/phenotype correlations in CSA. Further studies of CSA patients with data recorded in an international registry would be helpful to improve patient management and establish standardized guidelines.

Impact of high-risk thrombophilia status on recurrence among children with a first non-central-venous-catheter-associated VTE: an observational multicentre cohort study.

Deficiency of antithrombin (AT), protein C (PC) or protein S (PS) constitutes a major risk factor for venous thromboembolism (VTE). Individuals at high risk for recurrence who benefit from screening need to be identified. The primary study objective was to determine the individual recurrence risk among children with a first non-central-venous-catheter-associated VTE with respect to their thrombophilia status and to evaluate if the clinical presentation at first VTE onset differs between children with AT, PC or PS deficiency versus no thrombophilia. We calculated the absolute risk of VTE recurrence and event-free-survival adjusted for thrombophilia, age, sex and positive family VTE history in 161 consecutively enrolled paediatric VTE patients. The presence of a deficiency relative to no thrombophilia was evaluated as a potential predictor of recurrence. Predictors for recurrence were AT deficiency (hazard ratio/95% CI: 6·5/2·46-17·2) and female gender (2·6/1·1-6·35). The annual recurrence rates (95% CIs) were 5·4% (2·6-10) in AT-deficient children, 1·3% (0·3-3·8) in patients with PC deficiency, 0·7% (0·08-2·4) in the PS-deficient cohort and 0·9% (0·4-1·8) in patients with no thrombophilia. Positive family VTE history or combined thrombophilias did not predict recurrence. Given the overall annual incidence rate of recurrence of 1·5% we suggest screening for AT deficiency in children with VTE.

Impact of high risk thrombophilia status on recurrence among children and adults with VTE: An observational multicenter cohort study.

BACKGROUND: Antithrombin [AT]-, protein C [PC]- or protein S [PS]-deficiency [D] constitutes a major risk factor for venous thromboembolism [VTE]. Primary study objective was to evaluate if the clinical presentation at first VTE onset differs between children and adults and to compare the individual recurrence risk among patients with respect to age at onset and their thrombophilia status ATD, PCD or PSD. METHODS/PATIENTS/RESULTS: In 137 of 688 consecutively enrolled pediatric and adult VTE patients we calculated the absolute risk of VTE recurrence and event-free-survival adjusted for thrombophilia and positive family VTE history. At first VTE children manifested i) with a lower rate of pulmonary embolism, ii) a higher rate of cerebral vascular events or multiple VTEs, and iii) showed a higher proportion of unprovoked VTE compared to adolescents and adults. Adult patients reported more often a positive VTE history compared to younger study participants. The adjusted odds of recurrence in adults was 2.05 compared to children. CONCLUSION: At disease manifestation children and adults differ with respect to i) thrombotic locations, ii) percentage of unprovoked versus provoked VTE, and iii) different rates of positive VTE family histories. Furthermore, adults showed a two-fold increase risk of VTE recurrence compared to children.

Testing for inherited platelet defects in clinical laboratories in Germany, Austria and Switzerland. Results of a survey carried out by the Permanent Paediatric Group of the German Thrombosis and Haemostasis Research Society (GTH).

Inherited platelet defects are a rare and heterogeneous group of disorders. The majority of affected patients present with mild to moderate bleeding tendencies. However, in trauma and surgery, bleeding may be difficult to control. Laboratory tests for diagnosis are necessary for the prevention and treatment of critical bleeding. The aim of the THROMKID study was to obtain information on the means of investigating platelet function employed by clinical centres in German-speaking countries. For this purpose a patterns-of-practice survey was conducted from 2005 to 2007, the results of which are reported here. A total of 37 out of 41 identified clinical centers serving 98 million people completed the survey questionnaire. The number of tests offered for assessment of platelet function varied between 1 and 11, median 4. Aggregometry continued to be the most popular and helpful technique for evaluation of suspected platelet function disorders (100%). The PFA-100(R) CT (76%) and in vivo bleeding time (54%) were used to screen patients with suspected platelet function disorders. Selection of tests was based on a case-by-case decision at most centres (82%). The majority of centres performed specific platelet function tests less than 50 times per month. This survey illustrates the preferences of clinical centres in the selection, performance and interpretation of platelet function tests. These practices may considerably influence the detection and diagnosis of platelet function disorders. There is an urgent need for existing tests to be improved and new, fast and reliable tests of platelet function to be developed.

Clinical Perspective on Primary Angiitis of the Central Nervous System in Childhood (cPACNS).

Non-arteriosclerotic arteriopathies have emerged as important underlying pathomechanism in pediatric arterial ischemic stroke (AIS). The pathogenesis and classification of cerebral arteriopathies in childhood are heterogeneous. Different classifications base on (i) the anatomic site; (ii) the distribution and size of the affected vessel; (iii) the time course, for example, transient vs. progressive, monophasic vs. recurrent; (iv) the putative pathogenesis; (v) the magnetic resonance imaging morphology of the vasculopathies. Inflammation affecting the cerebral vessels is increasingly recognized as common cause of pediatric AIS. Primary cerebral vasculitis or primary angiitis of the central nervous system (CNS) in childhood (cPACNS) is an important differential diagnosis in pediatric AIS. Primary angiitis of the CNS is a rare disorder, and the pathogenesis is poorly understood so far. The current classification of cPACNS is based on the affected cerebral vessel size, the disease course, and angiographic pattern. Two large subtypes are currently recognized comprising large- and medium-sized vessel CNS vasculitis referred to as angiography-positive cPACNS and angiography-negative small vessel cPACNS. As the clinical manifestations of cPACNS are rather diverse, precise diagnosis can be challenging for the treating pediatrician because of the lack of vital laboratory tests or imaging features. Initial misdiagnosis is common because of overlapping phenotypes and pediatric AIS mimics. As untreated cPACNS is associated with a high morbidity and mortality, timely diagnosis, and induction of immunomodulatory and symptomatic therapy are essential. Survival and neurological outcome depend on early diagnosis and prompt therapy. Primary angiitis of the central nervous system in childhood differs in several aspects from primary cerebral angiitis in adults. The aim of this article is to give a brief comprehensive summary on pediatric primary cerebral vasculitis focusing on the clinical perspective regarding the classification, the putative pathogenesis, the disease course, the diagnostic tools, and emerging treatment options. A modified terminology for clinical practice is discussed.

Clinical and laboratory phenotypes associated with the aspirin-like defect: a study in 17 unrelated families.

Aspirin-like defect (ALD) is a rare, mostly autosomal dominant inherited dysfunction of the intraplatelet arachidonic acid (AA) pathway leading to impaired thromboxane A2 signalling. We aimed to establish diagnostic criteria for ALD diagnosis and present clinical and laboratory phenotypes of 52 individuals from 17 unrelated families. Platelet in vitro function was determined on the basis of platelet aggregation response (PAR) to AA, adenosine diphosphate, collagen and ristocetin as well as PFA-100 closure times (CT). Using impaired PAR to AA (< or =10%) as the mandatory diagnostic criterion, ALD could be confirmed in 17 patients. Subsequently, family members were investigated and among 35 individuals an additional 13 ALD patients as well as 4 individuals with mild ALD (PAR to AA: 19-32%) were identified. At least one bleeding symptom was reported by 25 (74%) ALD patients and prolonged CT was detected in 24 (71%) of the cases, both significantly correlated with impaired PAR to AA (P = 0.001 and P = 0.002, respectively). An estimated 0.6% prevalence was determined for ALD in our paediatric patients with suspected coagulation disorders. Due to the mild bleeding symptoms, ALD is probably underdiagnosed. If ALD is suspected, PAR to AA is suitable for the identification of individuals at risk of increased haemorrhage.

Modulation of adenine nucleotide concentrations in human plasma by erythrocytes and endothelial cells.

The regulation of plasma concentrations of adenine nucleotides is unsettled. We tested the possibility of extracellular adenosine triphosphate (ATP) production from adenosine diphosphate (ADP) at physiological low concentrations by erythrocytes and endothelial cells. Filtered erythrocytes and human umbilical vein endothelial cells (HUVEC) were incubated for 15 to 120 s with ADP (10 microM), supplemented with 3H-ADP (2.85 nM) or 14C-ADP (54.6 nM). Enzymatic conversion of ADP to ATP was detected by recovery of the radioactive label in the ATP fraction. ATP was measured in the supernatant using high performance liquid chromatography (HPLC) separation, scintillation techniques, and luminometry. Using etheno (epsilon)-labeled ADP (10 microM), the extracellular localization of the conversion was further corroborated. Following ADP application in plasma, no radioactivity was detected in the ATP fraction. However, in erythrocyte suspensions, 12.9% and 9.7% of the label were recovered in the ATP fraction after application of 3H- and 14C-ADP, respectively. Between 15 and 120 s after 3H-ADP application, the 3H-ATP fraction was found to be stable at around 10%. For the range of ADP concentrations studied (10-40 microM), no saturation of ATP production was achieved. The extracellular localization of conversion was supported by the recovery of the epsilon -label in the epsilon -ATP fraction. In contrast, on HUVEC a conversion of epsilon -ADP to epsilon -ATP was not observed. In conclusion, on erythrocytes there is rapid enzymatic conversion of extracellular ADP to ATP which may play a significant role in adjusting adenine nucleotide concentrations in human plasma. In endothelial cells, extracellular conversion of ADP to ATP is of quantitatively minor importance, if it contributes at all.

The impact of single nucleotide polymorphisms of the thrombin activatable fibrinolysis inhibitor (TAFI) gene on TAFI antigen levels in healthy children and pediatric oncology patients.

The thrombin activatable fibrinolysis inhibitor (TAFI) influences the pathways regulating fibrin formation and deposition. The enormous TAFI plasma level variability present in adults may be explained by a combination of two polymorphisms in the TAFI gene (+1542C>G; 505G>A). We aimed to correlate these two polymorphisms with plasma TAFI antigen concentrations in healthy children and pediatric oncology patients with and without venous thrombosis who were supplied with Broviac central venous catheters. Polymorphisms were detected by restriction fragment length polymorphism (RFLP) analysis of polymerase chain reaction (PCR) amplification, whereas TAFI concentration was determined using a commercial enzyme-linked immunosorbent assay (ELISA). Samples from 57 controls and 67 pediatric patients (11 venous thrombotic complications) were studied. TAFI levels in healthy children and patients were not influenced by gender or age. Compared with the 505GG carriers (wild type), 505AA carriers as well as heterozygous 505GA carriers each exhibited significantly higher TAFI antigen concentrations. In contrast, the lowest TAFI levels were detected in homozygous carriers of the +1542GG polymorphism. A combination of the genotype 505AA (homozygous carrier) and +1542CC (wild type) was present in 13 probands and resulted in the highest TAFI levels. Although in oncologic patients the risk of thrombosis was markedly increased by the heterozygous factor V 1691G>A mutation, the two TAFI polymorphisms investigated exerted no thrombogenic influence.