Marjolein Peters

Factor VIII gene (F8) mutation and risk of inhibitor development in nonsevere hemophilia A

Neutralizing antibodies (inhibitors) toward factor VIII form a severe complication in nonsevere hemophilia A, profoundly aggravating the bleeding pattern. Identification of high-risk patients is hampered by lack of data that take exposure days to therapeutic factor VIII concentrates into account. In the INSIGHT study, we analyzed the association between F8 mutation and inhibitor development in patients with nonsevere hemophilia A (factor VIII 2-40 IU/dL). This analysis included 1112 nonsevere hemophilia A patients from 14 centers in Europe and Australia that had genotyped at least 70% of their patients. Inhibitor risk was calculated as Kaplan-Meier incidence with cumulative number of exposure days as the time variable. During 44 800 exposure days (median, 24 exposure days per patient; interquartile range [IQR], 7-90), 59 of the 1112 patients developed an inhibitor; cumulative incidence of 5.3% (95% confidence interval [CI], 4.0-6.6) after a median of 28 exposure days (IQR, 12-71). The inhibitor risk at 50 exposure days was 6.7% (95% CI, 4.5-8.9) and at 100 exposure days the risk further increased to 13.3% (95% CI, 9.6-17.0). Among a total of 214 different F8 missense mutations 19 were associated with inhibitor development. These results emphasize the importance of F8 genotyping in nonsevere hemophilia A.

Mutations in the thrombopoietin receptor, Mpl, in children with congenital amegakaryocytic thrombocytopenia

Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare disorder of undefined aetiology. The disease presents with severe thrombocytopenia and absence of megakaryocytes in the bone marrow. Furthermore, CAMT patients may develop bone marrow aplasia. To obtain more insight into the mechanism underlying CAMT, five children were analysed. All patients had increased plasma thrombopoietin (Tpo) levels, indicating a platelet production defect. Bone marrow‐derived CD34+ stem cells from three patients were cultured in an in vitro liquid culture system to study megakaryocytopoiesis. CD34+ cells from two of the three patients failed to differentiate into megakaryocytes. The lack of megakaryocyte formation could imply that a defect in the c‐mpl gene, encoding the Tpo receptor, exists. Sequencing of c‐mpl revealed mutations in four of five patients. Three patients had point mutations and/or a deletion in the coding regions of c‐mpl. All point mutations led to an amino acid substitution or to a premature stop codon. In one patient, a homozygous mutation in the last base of intron 10 was found that resulted in loss of a splice site. This study showed that mutations in c‐mpl could be the cause of thrombocytopenia in CAMT in the majority of patients. Furthermore, Tpo has been shown to have an anti‐apoptotic effect on stem cells. Therefore, mutations in c‐mpl might not only affect megakaryocyte formation but may also impair stem cell survival, which could explain the occurrence of bone marrow failure as final outcome in patients with CAMT.

Inter‐individual variation in half‐life of infused recombinant factor VIII is related to pre‐infusion von Willebrand factor antigen levels

Summary. In an attempt to explain the substantial inter‐individual variability in half‐life of infused factor VIII (FVIII) among haemophilia A patients, we studied the correlation of pre‐infusion von Willebrand factor antigen (vWFAg) levels and the half‐life of a recombinant‐DNA‐derived FVIII (r‐VIII SQ, Pharmacia, Sweden). Intra‐individual variation in half‐life was small (range of variation 0.2‐1 h) in 12 severely affected haemophiliacs who received two doses of FVIII concentrate. In contrast, inter‐individual variation in half‐life was large (range of half‐lives 6‐28.8 h). A strong correlation between half‐life and pre‐infusion vWFAg levels was present (r= 0.87, P= 0.0003). We conclude that the half‐life of infused recombinant FVIII is related to pre‐infusion vWFAg levels in severely affected haemophilia A patients.

Obesity: a new disaster for haemophilic patients? A nationwide survey

Summary.  The prevalence of obesity, an important risk factor for both cardiovascular disease and arthropathy, is strongly increasing in the general population, but data for the haemophilia population are scarce. Obesity may have a more profound effect on arthropathy and on cardiovascular disease in patients with haemophilia. To assess the prevalence of obesity in haemophilia patients and install adequate measures, if necessary. We performed a nationwide postal survey to measure the prevalence of overweight and obesity in Dutch haemophilia patients in 1992 (n = 980) and 2001 (n = 1066). A random sample of the Dutch male population served as the control group. In adult haemophiliacs, the prevalence of overweight (BMI 25–30 kg m−2) increased from 27% to 35% (95% CI 31.1–38.0) and the prevalence of obesity (BMI ≥30 kg m−2) doubled from 4% to 8% (95% CI 6.0–10.1), which was comparable with the general population. The increased prevalence of obesity in boys with haemophiliacs, which tripled in 10 years, is alarming. The increased prevalence of overweight and obesity in patients with haemophilia may have a profound effect on morbidity and quality of life of haemophilia patients by aggravating pre‐existing arthropathy and predisposing aged patients to cardiovascular disease. Measures to prevent overweight in haemophiliacs are therefore urgently needed.

Quality of life of female caregivers of children with sickle cell disease: a survey

This Dutch survey demonstrates a lower quality of life in female caregivers of children with sickle cell disease than in the healthy female population and caregivers of healthy children with the same socioeconomic status. Therefore, better support is needed to improve the quality of life of both children with sickle cell disease and their caregivers. Caring for a child with sickle cell disease poses extra demands on parents, both practically and psychologically, which may influence their quality of life. Since families of children with sickle cell disease in the Netherlands usually belong to immigrant communities with a low socio-economic status, there may be an additional strain on caregivers. The aim of the present study was to evaluate the quality of life of caregivers of children with sickle cell disease. The quality of life of female caregivers of sickle cell disease patients, measured with the TNO-AZL Adult Quality of Life questionnaire, was compared to the norm data of healthy Dutch females (n=700) and female caregivers of healthy children with the same socio-economic status and ethnic background (socio-economic status control group). Groups were compared by the Mann-Whitney U test. Point estimates and 95% confidence intervals of the median difference are presented. The results of questionnaires of 54 caregivers of children with sickle cell disease and 28 caregivers of a control group of the same socio-economic status were analyzed. Caregivers of patients with sickle cell disease had a significantly lower quality of life on all subscales compared to the Dutch norm population. Compared to the control group of the same socio-economic status, the quality of life of caregivers of patients with sickle cell disease was significantly lower on the subscales depressive moods, daily activities and vitality. In this first study reporting on the quality of life of caregivers of children with sickle cell disease, we demonstrate a reduced quality of life in these caregivers compared to the healthy Dutch female population and caregivers of healthy children with the same socio-economic status.

Diagnosis and management of haemophilia

#### Summary points Haemophilia, which means love (“philia”) of blood (“haemo”), is associated with prolonged and excessive bleeding. It is a hereditary disorder of haemostasis that occurs in one in 5000 men (prevalence of 10 in 100 000 people) and is caused by a deficiency of clotting factor VIII (in haemophilia A) or factor IX (in haemophilia B) as a result of defects in the F8 and F9 genes. Basic knowledge of the inheritance and management of haemophilia is essential for a broad group of healthcare workers, because severe or even life threatening bleeding can be prevented if the condition is adequately diagnosed and promptly treated. Furthermore, in women carriers who have an affected fetus, special precautions are needed to prevent perinatal bleeding in both the mother and the newborn baby. This review presents current recommendations for the diagnosis and management of haemophilia, which are generally based on observational studies and case series because few randomised clinical trials have been published in this relatively rare disease. #### Sources and selection criteria We searched Medline and the Cochrane Database of Systematic …

Neurocognitive deficits in children with sickle cell disease: a comprehensive profile†

Sickle cell disease (SCD) can lead to profound cerebral damage, associated with neurocognitive deficits. The aim of the current study was to evaluate a broad range of neurocognitive functions in children with SCD compared to a SES‐matched control group, in order to gain more insight into the specific deficits of these patients.

Persistent antithrombin III deficiency: Risk factor for thromboembolic complications in neonates small for gestational age

Coagulation and fibrinolytic factors were investigated daily in 24 SGA and 26 AGA neonates. The results were correlated with placental form and structure and with hematologic values. In the SGA infants, a higher incidence of placental infarction (P less than 0.01), polycythemia (P less than 0.005), and thrombocytopenia (P less than 0.001) was present. During the first 9 days, the mean antithrombin III level in the AGA group increased from 0.36 to 0.53 U/ml, whereas in SGA neonates this value was initially significantly lower (0.27 U/ml) and remained at that level for the entire observation period. The same pattern was found for alpha 2-antiplasmin. The persistent AT-III deficiency and reduced blood flow associated with polycythemia may explain the increased risk of thromboembolic complications in SGA infants described by others.

Low Antithrombin III Levels in Neonates with Idiopathic Respiratory Distress Syndrome: Poor Prognosis

Summary: Automated microanalytic chromogenic coagulation assays allow serial monitoring of critically ill newborn infants. In this study 84 premature infants [26 healthy prematures and 58 neonates with idiopathic respiratory distress syndrome (IRDS)] were studied daily during the first week of life, to investigate the possible significance of hemostatic abnormalities in IRDS.In neonates with IRDS, coagulation factors II and X, antithrombin III (AT-III), plasminogen, and α2-antiplasmin were significantly lower than control values. Recovery of the initially low AT-III levels was delayed relative to the other coagulation parameters measured. An AT-III < 0.15 U/ml was present within the first 6 h of life in eight patients who developed IRDS, seven of whom died within 48 h. Autopsy of these neonates showed widespread fibrin deposition and hemorrhage in vital organs consistent with intravascular coagulation. These findings indicate that very low levels of AT-III are associated with disseminated intravascular coagulation in neonates with IRDS and suggest that a deficiency of AT-III is predictive of a poor outcome.

Rapid microanalysis of coagulation parameters by automated chromogenic substrated methods - application in neonatal patients

Daily monitoring of coagulation parameters in critically ill premature born neonates is only possible on small amounts of blood obtained by heelpuncture. Therefore, automated spectrophotometric micro-assays for antithrombin III (AT III), factors II and X, plasminogen and alpha 2 antiplasmin were applied on capillary and venous blood samples concurrently obtained in adults and healthy neonates. No statistically significant difference for any of the parameters was revealed. High levels of platelet factor 4 present in serial capillary samples of adults, did not interfere with the heparin dependent AT III assay. There was no evidence of thrombin or thromboplastin generation in these capillary samples, when examined for Va or VII activities. The levels of AT III, factors II and X and of plasminogen in neonates were 35-45% of the adult levels, in contrast to alpha 2 antiplasmin which was in the adult range.