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Hemophilia A is an X-Iinked bleeding disorder, caused by deficient or defective blood coagulation factor VIII. The most characteristic symptoms of the severe forms of hemophilia A are joint and muscle bleeds. Intracranial hemorrhage occurs only in 3-10% of the patients. Spinal epidural hematomas are rarely seen. We describe a 13-month-old boy with hemophilia A who was admitted to the hospital because of irritability and unspecified pain for the past two days. There was no history of evident trauma, no fever. Physical investigation showed no skin lesions or hematomas and no obvious cause for the pain. Neurological examination showed a dysphoric toddler, mainly in the fetal position. No neurological abnormalities were found except for a miosis of the right pupil due to a suspected Homer syndrome. Magnetic resonance imaging of the spine showed an extensive epidural hematoma. The boy was successfully treated with intensive replacement therapy during three weeks and did not require surgical intervention. There was a rapid and complete clinical resolution. In conclusion, rare hematomas should be considered and searched for in children with bleeding disorders and not well understood complaints. Early diagnosis is important for the neurological outcome. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to an article about the rare complication of allogeneic bone marrow transplant.

In population pharmacokinetic (PK) models, interindividual variability is explained by implementation of covariates in the model. The widely used forward stepwise selection method is sensitive to bias, which may lead to an incorrect inclusion of covariates. Alternatives, such as the full fixed effects model, reduce this bias but are dependent on the chosen implementation of each covariate. As the correct functional forms are unknown, this may still lead to an inaccurate selection of covariates. Machine learning (ML) techniques can potentially be used to learn the optimal functional forms for implementing covariates directly from data. A recent study suggested that using ML resulted in an improved selection of influential covariates. However, how do we select the appropriate functional form for including these covariates? In this work, we use SHapley Additive exPlanations (SHAP) to infer the relationship between covariates and PK parameters from ML models. As a case‐study, we use data from 119 patients with hemophilia A receiving clotting factor VIII concentrate peri‐operatively. We fit both a random forest and a XGBoost model to predict empirical Bayes estimated clearance and central volume from a base nonlinear mixed effects model. Next, we show that SHAP reveals covariate relationships which match previous findings. In addition, we can reveal subtle effects arising from combinations of covariates difficult to obtain using other methods of covariate analysis. We conclude that the proposed method can be used to extend ML‐based covariate selection, and holds potential as a complete full model alternative to classical covariate analyses. [ABSTRACT FROM AUTHOR]

Nonlinear mixed effect (NLME) models are the gold standard for the analysis of patient response following drug exposure. However, these types of models are complex and time‐consuming to develop. There is great interest in the adoption of machine‐learning methods, but most implementations cannot be reliably extrapolated to treatment strategies outside of the training data. In order to solve this problem, we propose the deep compartment model (DCM), a combination of neural networks and ordinary differential equations. Using simulated datasets of different sizes, we show that our model remains accurate when training on small data sets. Furthermore, using a real‐world data set of patients with hemophilia A receiving factor VIII concentrate while undergoing surgery, we show that our model more accurately predicts a priori drug concentrations compared to a previous NLME model. In addition, we show that our model correctly describes the changing drug concentration over time. By adopting pharmacokinetic principles, the DCM allows for simulation of different treatment strategies and enables therapeutic drug monitoring. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate participation in sports activities and risk-taking behaviour in children with haemophilia and the relationship to personal and health related factors. Ninety-nine children (mean age 12.6 years) completed questionnaires regarding participation in sports and physical education, medication, health related quality of life, and perceived motor competence. Furthermore, weight, height, active range of motion, pain, and muscle strength were assessed. Based on a risk exposure factor (REF) we defined subgroups with low, medium, and high risk when participating in sport. Most children participate in sport five times a week (mean 140 min per week), and little absence during school sports was reported. In general, prophylaxis was not tailored to sport activities. Boys with haemophilia preferred other sports than their Dutch contemporaries. The top-5 being soccer, swimming, tennis, gymnastics, and cardio-fitness for the former; soccer, gymnastics, tennis, hockey, and swimming for the latter. Significant differences between the low risk group and both other groups were found for sport intensity, total energy expenditure (EE) and average risk factor (ARF), however the medium and high-risk groups did not differ in ARF. REF and sport participation increased associated with increasing interest in athletic and motor activities. No significant differences were found between REF groups regarding age, Z-BMI, Z-AROM, Z-Muscle force, and the presence of painful joints. As in normal peers motivation to participate in sport depends upon the enthusiasm and interest, in children with haemophilia choice of sports differs, probably related to sport advice. [ABSTRACT FROM AUTHOR]

Introduction Patients', parents' and providers' preferences with regard to medical innovations may have a major impact on their implementation. Aim To evaluate barriers and facilitators for individualized pharmacokinetic (PK)-guided dosing of prophylaxis in haemophilia patients, parents of young patients, and treating professionals by discrete choice experiment (DCE) questionnaire. Patients/Methods The study population consisted of patients with haemophilia currently or previously on prophylactic treatment with factor concentrate ( n = 114), parents of patients aged 12-18 years ( n = 19) and haemophilia professionals ( n = 91). DCE data analysis was performed, taking preference heterogeneity into account. Results Overall, patients and parents, and especially professionals were inclined to opt for PK-guided dosing of prophylaxis. In addition, if bleeding was consequently reduced, more frequent infusions were acceptable. However, daily dosing remained an important barrier for all involved. 'Reduction of costs for society' was a facilitator for implementation in all groups. Conclusions To achieve implementation of individualized PK-guided dosing of prophylaxis in haemophilia, reduction of bleeding risk and reduction of costs for society should be actively discussed as they are motivating for implementation; daily dosing is still reported to be a barrier for all groups. The knowledge of these preferences will enlarge support for this innovation, and aid in the drafting of implementable guidelines and information brochures for patients, parents and professionals. [ABSTRACT FROM AUTHOR]

Introduction: Von Willebrand disease (VWD) type 2N is characterized by a defective binding of factor VIII (FVIII) to von Willebrand factor (VWF) resulting in diminished plasma FVIII levels and a clinical phenotype mimicking mild haemophilia A. Several mutations in the FVIII binding site of VWF have been reported. Aim: This study aims to examine the effect of genotype on clinical phenotype in a cohort of VWD 2N patients. Methods: Patients with at least one genetically confirmed 2N mutation were selected retrospectively from a cohort of patients with suspected VWD. Clinical and laboratory phenotypes including bleeding scores (BS) were obtained and analysed. Results: Forty-two VWD 2N patients with a mean age of 44 years were included. Eleven patients were homozygous or compound heterozygous (genetically confirmed group) and 31 patients were heterozygously affected (carriers group). Statistically significant differences between genetically confirmed VWD 2N patients and carriers were found in FVIII activity, VWF antigen levels, VWF-FVIII binding capacity, FVIII/VWF antigen ratio (all P<0.001), VWF-ristocetin activity (p=0.001) and VWF collagen binding ( P = 0.002). Median BS was 6 in genetically confirmed VWD 2N patients compared with 3 in carriers ( P = 0.047). Haemarthrosis, muscle haematomas and postpartum haemorrhage were only reported in genetically confirmed 2N patients. Conclusion: Phenotypic analysis showed that all laboratory parameters are lower in genetically confirmed VWD 2N patients compared with heterozygous 2N carriers. The clinical phenotype in genetically confirmed VWD 2N patients is comparable to mild haemophilia A patients and more severe than heterozygous 2N carriers. [ABSTRACT FROM AUTHOR]

Afibrinogenaemia is an autosomal recessive disease with an estimated prevalence of approximately one in a million. The most common symptoms of afibrinogenaemia are umbilical cord bleeding, bleeding into skin, mouth, muscles, gastrointestinal and genitourinary tracts and the central nervous system. Other recognized complications include; haemarthroses, spontaneous splenic rupture, epistaxis, menorrhagia, recurrent abortion and venous and arterial thromboembolism. Bone cysts have also been described as a rare complication of afibrinogenaemia. The aim of this study was to conduct a systematic literature review, summarize the reported cases and to report two new cases. Three electronic databases were searched for relevant publications: PubMed, Medline and EMBASE. The following search criteria were used: '(bone cysts OR intraosseous haematoma OR intraosseous haemorrhage) AND (afibrinogenaemia OR fibrinogen deficiency)'. The reference lists of the selected papers were searched for more relevant literature. In total, eight patients had bone cysts as complication of afibrinogenaemia and six of them suffered from pain in their extremities. Bone cysts were primarily located in the vicinity of the cortex or trabeculae in the diaphysis of the long bones, especially in the femora, tibiae and humeri. Some were regressive, probably due to reactive bone remodelling. A number of cysts were filled with serosanguinous fluid. It might be useful to check for bone cysts when patients with congenital afibrinogenaemia complain of 'rheumatic' pains in their extremities. Whole body magnetic resonance imaging is the diagnostic imaging technique of choice. Recurrent episodes of pain, but not radiological deterioration, appear to benefit from prophylactic therapy with fibrinogen concentrate. [ABSTRACT FROM AUTHOR]

. Rare bleeding disorders (RBDs) are a heterogeneous group of diseases with varying bleeding tendency, only partially explained by their laboratory phenotype. We analysed the separate groups of RBD abnormalities, and we investigated retrospectively whether the novel haemostasis assay (NHA) was able to differentiate between bleeding tendency. We have performed simultaneous thrombin generation (TG) and plasmin generation (PG) measurements in 41 patients affected with deficiencies in prothrombin, factor (F) V, FVII, FX, FXIII and fibrinogen. Parameters of the NHA were classified based on (major or minor) bleeding tendency. Patients with deficiencies in coagulation propagation (FII, FV and FX) and major type of bleedings had diminished TG (expressed as AUC) below 20% of control. FVII deficient patients only had prolonged thrombin lag-time ratio of 1.6 ± 0.2 ( P < 0.05) and normal AUC (92-125%). Afibrinogenemic patients demonstrated PG of 2-29% of normal and appeared to correlate with the type of mutation. Thrombin peak-height (57 ± 16%) was reduced (not significant) in these patients and AUC was comparable to the reference (102 ± 27%). FXIII-deficient plasmas resulted in a reduced thrombin peak-height of 59 ± 13% ( P < 0.05) and normal AUC (90 ± 14%). Thrombin peak-height ( P < 0.01) and plasmin potential ( P < 0.05) were lower in the major bleeders compared with the minor bleeders. These results provided distinct TG and PG curves for each individual abnormality and differentiation of bleeding tendency was observed for thrombin and PG parameters. Prospective studies are warranted to confirm these retrospective results. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented that discusses mutations in familial platelet disorder (FPD) with enhanced risk for acute myeloid leukemia (AML).

A letter to the editor about haemophilia in three premature infants is presented.