Genetic counseling of hemophilia carriers

Basic analysis of a potential carrier includes calculation of the probability, or odds, for carriership based on pedigree and clotting factor analysis. Genotype assessment constitutes a more accurate method of carrier detection. Where circumstances permit, the genetic diagnosis of hemophilia should be based on the direct identification of the pathogenic mutation in the factor (F) VIII gene. Neutral mutations in the FVIII gene and the risk of mosaicism (a mixture of normal and mutation carrying cells) in sporadic families may cause misclassification. If it is not possible to use the mutation for diagnostic purposes, it may be possible to use linked polymorphic markers (restriction fragment length polymorphisms [RFLP]) to trace the inheritance of the hemophilia gene within a pedigree. Linkage analysis is limited because of uninformative patterns of polymorphic markers, ethnic variation, linkage disequilibrium, and the need for participation of family members, and it is not useful in sporadic families, which constitute more than half of the hemophilia families. Potential carriers of hemophilia should be offered qualified assistance in genetic information, testing, and counseling to help them to cope with the psychological and ethical problems related to carriership of a genetic disorder.     

Bleeding manifestations in heterozygotes with congenital FVII deficiency: a comparison with unaffected family members during a long observation period*

Objectives: To determine whether heterozygotes with FVII deficiency have a bleeding tendency or not.

Patients and methods: Eighty-four patients (OK) heterozygous for FVII deficiency, at the onset of the study, were paired with unaffected family members and followed for a long period of time (mean 22.6 years) for the occurrence of bleeding. Diagnosis of heterozygosis had to be based on family studies, clotting, immunological assays and genetic analysis.

Results: The mean FVII activity level was 0.51?IU/dl (range 35–65) and 94?IU/dl (range 88–118) in the heterozygotes and in the normal counterparts, respectively. Documented bleeding manifestations occurred in eight heterozygotes and in seven normal subjects. Statistical analysis of the difference was not significant. Bleeding manifestations were easy bruising, bleeding after tooth extractions, menorrhagia, epistaxis with no difference among the two groups. There was no strict correlation between bleeding and FVII activity levels.

Conclusions: The study indicates that heterozygotes for FVII deficiency show rare bleeding manifestations which are also present in the unaffected family members with normal FVII levels. This indicates that Factor VII activity levels played no role in the occurrence of the bleeding symptoms. Furthermore, FVII levels of around 0.40?IU/dl are capable of assuring a normal hemostasis.     

Carrier detection for hemophilia B: evaluation of multiple polymorphic sites

DNA analysis was performed in families with hemophilia B. Restriction fragment length polymorphisms (RFLPs) produced by endonucleases Taql, Xmnl, and Ddel were studied by two factor IX genomic probes, F9(VIII) and F9(XIII). Fifty-seven subjects from ten families were investigated; of them, 31 were carriers (11 obligate and 20 potential). Of the potential carriers, ten displayed laboratory features allowing for a phenotypic diagnosis of heterozygosity. Segregation analysis of the markers was informative in 19/20 potential carriers, which belong to nine of the ten studied families. Among the potential carriers, Taql allowed the carriership assessment in 15 (78.9%), Xmnl in 15 (94.7%), and Ddel in two (10.4%). Diagnosis was not possible in one family since a homozygosity in the key individuals with all the employed enzymes (Taql, Xmnl, Ddel, + BamHI) was found. Hemophilia B syndrome in two families likely results from a new mutation. In one family, a first-trimester prenatal diagnosis was performed. The use of RFLP analysis allowed us to improve genetic counseling as compared with the phenotypic evaluation by clotting factor assays. Indeed, evaluation of RFLP increased by 26% the carriership assessment of the potential carriers of the hemophilia B trait.     

Use of porcine factor VIII in the treatment of patients with acquired hemophilia

Data have been collected from 47 centers in Europe and North America on the treatment with porcine factor VIII concentrate of 74 acute bleeding episodes in 65 patients with acquired hemophilia. The median initial anti-human factor VIII auto-antibody inhibitor level was 38 Bethesda unit (BU)/mL (range 1.2 to 1,024) whereas that against porcine was 1 BU/mL (range 0 to 15). The mean initial dose of porcine factor VIII infused was 84 IU/kg, which increased the plasma factor VIII:C activity by 0.85 IU/mL. Therapy was continued for a mean of 8.5 days during which time the average number of infusions was 11. Objective clinical responses were rated as good or excellent in 78% of recipients. Side effects were uncommon; only one patient experienced a severe anaphylactic reaction necessitating the discontinuation of porcine FVIII therapy. After therapy, no increase in the median level of anti- human FVIII or anti-porcine antibody was noted in the group as a whole, although 13 patients showed individual increases in either anti-human or anti-porcine antibody levels or both of more than 10 BU/mL. Of the 7 patients who subsequently rebled, 5 were successfully re-treated and 2 did not respond to further porcine factor VIII treatment. Porcine factor VIII is safe and clinically effective treatment for bleeding episodes associated with acquired hemophilia and should be considered as first-line therapy for patients whose acquired anti-factor VIII:C antibody cross-reacts with porcine factor VIII:C at low levels.     

A female hemophilia A combined with hereditary coagulation factor XII deficiency: a case report.

A 2-year-old Japanese girl with easy bruising and arthropathy was demonstrated to have severe hemophilia A (Factor VIII activity: less than 0.01 U/ml). She had normal 46XX karyotype. Her brother also had hemophilia A, and her mother and grandmother seem to be hemophiliac carriers. Additionally, activated partial thromboplastin time (APTT) of the patient was disproportionately prolonged and there were reduced levels of coagulation factor XII in the patients and members of the maternal trait which are compatible with heterozygous factor XII deficiency. Her father had both normal factor VIII and factor XII levels. Southern blotting analysis of genomic DNA from the propositus and family members with factor VIII and factor XII DNA probes revealed no gross alterations. This patient represents a female hemophilia A combined with heterozygous factor XII deficiency. Nonrandom inactivation of a normal X-chromosome (extreme lyonization) may be the basis for the expression of hemophilia A in this female patient.     

Carrier detection in hemophilia A: a cooperative international study. I. The carrier phenotype

Eight laboratories in six countries cooperated to clarify several issues concerning the phenotypes of heterozygous carriers of hemophilia "A." Plasma levels of factor VIII (F.VIII:C, formerly VIII:C) and von Willebrand factor (VWF:Ag, formerly VIIIR:Ag) of carriers and normal women were determined by various "in-house" methods; a single lyophilized plasma standard was used for all assays. Analysis of the collated data from 336 carriers (296 obligatory carriers and 40 sporadic carriers) and 137 normal women showed that there was no difference in the F.VIII:C levels of "paternal" carriers (women who had obtained the abnormal gene from their fathers) and "maternal" carriers. Neither was there a difference in the VWF:Ag levels of normal women and either type of carrier. Age was found to have a significant effect on both F.VIII:C and VWF:Ag, values being higher at very young and very old ages, the minima occurring in the 25- to 30-year range. ABO blood type had a striking effect. Women of types A, B, and AB (designated non- O in the study), both normals and carriers, had significantly higher levels of both factors than did women of type O. Analysis by laboratories showed that differences in mean levels of both factors between laboratories were highly significant. It was concluded that age, ABO blood type, and laboratory variation should be taken into account in carrier detection.     

Cost-effectiveness in establishing hemophilia carrier detection and prenatal diagnosis services in a developing country with limited health resources

The cost-effectiveness of carrier detection and prenatal diagnosis for hemophilia at the International Hemophilia Training Center, Bangkok, Thailand was studied. From 1991 to 2002, 209 females from 124 families with hemophilia A and B were included. There were 180 hemophilia A carriers and 29 hemophilia B carriers which could be classified into 78 obligate and 131 possible carriers. The phenotypic analysis for possible carriers involved the determination of levels of factor VIII or IX clotting activity (FVIII:C, FIX:C) and the ratio of FVIII:C and von Willebrand factor antigen. The result revealed that 49 females (37.4%) were diagnosed as carriers, 65 females (49.6%) were normal and 17 females (13%) were undetermined. Additional genotypic analysis was provided to 46 families with 74 females with obligate, proven or undetermined carriers within the reproductive life. The polymorphisms associated with factor VIII and IX genes were used including Bcl I for the factor VIII gene and combined use of Mse I, Sal I, Nru I, Hha I and Dde I for the factor IX gene. The informative rate was 59.4% (44/74). Consequently, 12 prenatal diagnoses for fetus at risk were performed. Sex determination was initially determined and followed by the diagnosis of hemophilia through informative gene tracking and/or the measurement of fetal levels of FVIII:C or FIX:C. The result revealed that 3 male fetuses were affected. The total cost of carrier detection and prenatal diagnosis that the families had to pay in the government hospital was 238,600 Baht (US dollars 5,965). It was compared to the estimated cost of minimal replacement therapy using lyophilized cryoprecipitate for the survival time of 30 years in one patient with hemophilia of 1,012,500 Baht (US dollars 25,312.5). The cost of prevention was much less than the replacement therapy. In conclusion, it is cost-effective to establish the service for carrier detection and prenatal diagnosis for hemophilia especially in developing countries with limited health resources.     

Therapeutic factor VIII levels and negligible toxicity in mouse and dog models of hemophilia A following gene therapy with high-capacity adenoviral vectors

High-capacity adenoviral (HC-Ad) vectors expressing B-domain-deleted human or canine factor VIII from different liver-specific promoters were evaluated for gene therapy of hemophilia A. Intravenous administration of these vectors into hemophilic FVIII-deficient immunodeficient SCID mice (FVIIIKO-SCID) at a dose of 5 x 10(9) infectious units (IU) resulted in efficient hepatic gene delivery and long-term expression of supraphysiologic FVIII levels (exceeding 15 000 mU/mL), correcting the bleeding diathesis. Injection of only 5 x 10(7) IU still resulted in therapeutic FVIII levels. In immunocompetent hemophilic FVIII-deficient mice (FVIIIKO), FVIII expression levels peaked at 75 000 mU/mL but declined thereafter because of neutralizing anti-FVIII antibodies and a cellular immune response. Vector administration did not result in thrombocytopenia, anemia, or elevation of the proinflammatory cytokine interleukin-6 (IL-6) and caused no or only transient elevations in serum transaminases. Following transient in vivo depletion of macrophages before gene transfer, significantly higher and stable FVIII expression levels were observed. Injection of only 5 x 10(6) HC-Ad vectors after macrophage depletion resulted in long-term therapeutic FVIII levels in the FVIIIKO and FVIIIKO-SCID mice. Intravenous injection of an HC-Ad vector into a hemophilia A dog at a dose of 4.3 x 10(9) IU/kg led to transient therapeutic canine FVIII levels that partially corrected whole-blood clotting time. Inhibitory antibodies to canine FVIII could not be detected, and there were no signs of hepatotoxicity or of hematologic abnormalities. These results contribute to a better understanding of the safety and efficacy of HC-Ad vectors and suggest that the therapeutic window of HC-Ad vectors could be improved by minimizing the interaction between HC-Ad vectors and the innate immune system.     

Association of the hemophilia A carrier state and hemorrhagic thrombocytopathy with dilatation of the platelet membrane complex

Associations of hereditary abnormalities of the factor VIII complex and hereditary platelet disorders have previously been reported in 12 families. Another family is reported in which 6 members had a bleeding tendency and thrombocytopathy characterized by impaired platelet aggregation and dilatation of the platelet membrane complex. Apart from the platelet function abnormalities the proband had diminished levels of factor VIII clotting activity (36 U/dl) and factor VIII clotting antigen (31%) while factor VIII-related antigen and ristocetin cofactor were normal. The other affected family members had normal levels of factor VIII:C. Consequently, the proband was defined as a hemophilia A carrier manifesting also hereditary thrombocytopathy.     

Haemophilia B carrier detection by factor IX:C analysis; no impact of the type of mutation or severity of disorder

Haemophilia B, an X-linked recessive bleeding disorder characterized by lack or deficiency of factor IX, has been shown to be caused by any of a variety of DNA abnormalities (partial or total deletions, nonsense or missense mutations). Since in most countries carrier detection is based on factor IX coagulant activity (FIX:C) assay, this study was designed to determine whether carriers' FIX:C values are dependent on the severity of haemophilia (mild, moderate or severe) or on the genetic anomaly in the family. FIX:C concentrations were studied in 28 obligate carriers, 39 women known to carry the mutation and 33 verified noncarriers subgrouped by severity of disorder or genetic anomaly. No significant subgroup differences in FIX:C values were found, thus suggesting the level of FIX:C concentrations in carriers to be unaffected by the severity of haemophilia, or by its expression (i.e. deficient or dysfunctional factor IX). The specificity and sensitivity of FIX:C analysis for the purpose of carrier diagnosis was judged by receiver operating characteristic curve analysis, where an FIX:C cut-off level of 75 IU dL-1 was found to be optimal (sensitivity 93% and specificity 88%).     

Increased risk for fetal loss in carriers of the factor V Leiden mutation.

BACKGROUND: An increased risk for fetal loss caused by placental thrombosis is probable in carriers of the factor V Leiden mutation but has not been demonstrated consistently in previous studies. OBJECTIVE: To determine the overall risk for fetal loss and the separate risks for miscarriage and stillbirth in carriers of the factor V Leiden mutation. DESIGN: Retrospective cohort study. SETTING: Three university hospitals. PARTICIPANTS: 228 carriers of the factor V Leiden mutation (77 propositi, 151 relatives) and 121 noncarrier relatives (controls). All participants had been pregnant at least once. MEASUREMENTS: Risks for fetal loss, miscarriage (defined as fetal loss within 20 weeks of gestation), and stillbirth (defined as fetal loss after >20 weeks of gestation) in women and in pregnancies were estimated and compared in carriers and noncarriers. Adjusted odds ratios were calculated by using multiple regression analysis. A random-effects model was used for comparisons of pregnancies. RESULTS: Fetal loss occurred in 31.6% of carriers and 22.3% of noncarriers, miscarriage occurred in 29.4% of carriers and 17.4% of noncarriers, and stillbirth occurred in 5.7% of carriers and 5.0% of noncarriers. Fetal loss recurred in 10.1% of carriers and 4.1% of noncarriers (odds ratio, 2.60 [95% CI, 0.96 to 7.03]). Adjusted odds ratios were 2.12 (CI, 1.35 to 3.33) for fetal loss, 2.08 (CI, 1.33 to 3.25) for miscarriage, and 1.60 (CI, 0.58 to 4.43) for still-birth when pregnancies in carriers and noncarriers were compared. Homozygous carriers had a greater risk for fetal loss (odds ratio, 2.01 [CI, 0.94 to 4.32]) and stillbirth (odds ratio, 4.85 [CI, 0.82 to 25.58]) than heterozygous carriers. CONCLUSIONS: Carriers of the factor V Leiden mutation have a greater risk for fetal loss (particularly miscarriage) than noncarriers. These data further suggest a greater risk for recurrence of fetal loss in carriers than in noncarriers and a greater risk for fetal loss and stillbirth in homozygous carriers than in heterozygous carriers.     

Effect of danazol on clotting factor levels, bleeding incidence, factor infusion requirements, and immune parameters in hemophilia

Several recent studies have reported conflicting results on the effectiveness of danazol, an attenuated androgen, in raising plasma levels of clotting factors VIII and IX in patients with hemophilia. We undertook a randomized, double-blind cross-over trial using 8 weeks' administration of danazol (D), 600 mg/d, and 8 weeks' administration of placebo (P) separated by 2 weeks of rest in 12 patients with hemophilia A and four patients with hemophilia B. Plasma factor VIII and IX levels, frequency and type of bleeding episodes, amount of factor concentrate infused, fibrinogen, fibrinolysis assays, antithrombin III, liver function, and immune parameters were followed. During the danazol phase a minimal increase was noted in the average clotting factor levels, an increase that, although statistically significant, was of hemostatically marginal magnitude. Significant increases in protein C and plasminogen levels, however, were observed during the danazol period, suggestive of danazol-mediated enhanced fibrinolysis. Clinically, bleeding frequency was significantly increased, and more clotting factor was consumed during the danazol period. Furthermore, eight episodes of hematuria and oral mucosal bleeding was reported during the danazol phase in contrast to only one episode of hematuria during the placebo phase, consistent with an enhancement of fibrinolytic activity with danazol. We conclude that danazol does not have a hemostatically significant effect on plasma levels of factor VIII and IX but may be associated with enhancement of fibrinolytic activity, resulting in increased bleeding frequency and requiring more clotting factor infusions. Therefore, danazol is not a viable alternative in the treatment of hemophilia.     

Incidence of venous thromboembolism in asymptomatic family members who are carriers of factor V Leiden: a prospective cohort study

In a prospective cohort study, we assessed the incidence of spontaneous and risk period-related venous thromboembolism (VTE) in asymptomatic family members of patients who experienced VTE and had the factor V Leiden mutation. In all, 561 family members of 131 probands were included, 313 of whom were carriers (299 heterozygous and 14 homozygous) and 248 of whom were noncarriers of the factor V Leiden mutation. Average follow-up was 4 years (range, 4 months-6 years). There were 1255 and 984 observation-years of follow-up in carriers and noncarriers, respectively. Eight episodes of VTE occurred in heterozygous carriers, resulting in an annual incidence of 0.67% (95% confidence interval [CI], 0.29-1.33). Two events occurred in the absence of associated risk factors, determining an annual incidence of spontaneous VTE of 0.17% (95% CI, 0.02-0.6). Only one VTE (risk period-related) occurred in noncarriers, with an annual incidence of 0.1% (95% CI, 0.003-0.56). Relative risk for VTE in heterozygous carriers compared with noncarriers of the factor V Leiden mutation was 6.6 (95% CI, 1.1-39.8). Risk period-related VTE occurred with an incidence of 18% and 5% per risk period in heterozygous carriers and in noncarriers, respectively. Thus, the low rate of VTE in asymptomatic family members carrying the mutation did not justify continuous anticoagulant prophylaxis. Screening families of symptomatic probands with the factor V Leiden mutation has the potential to identify those asymptomatic carriers who might benefit from thromboprophylaxis during risk periods.     

Endoscopic sphincterotomy in adult hemophiliac patients with choledocholithiasis

BACKGROUND: The aim of this study was to investigate the risk of bleeding in adult hemophiliac patients undergoing endoscopic sphincterotomy for choledocholithiasis. METHODS: From 1983 to 2002, 7 patients with hemophilia A and two with hemophilia B were referred for endoscopic sphincterotomy and extraction of bile duct stones. The degree of hemophilia was mild in 4 patients, moderate in 3, and severe in two. Pre-admission levels of blood clotting factors ranged from less than 1% to 18%. Levels of the deficient factors were monitored carefully before and after sphincterotomy, and the relevant factor was replaced to achieve 100% activity before and for 24 hours after endoscopic sphincterotomy. OBSERVATIONS: Seven patients had factor replacement every 8 hours, and two received continuous infusions. No patient developed bleeding after sphincterotomy. At discharge, 48 hours after the procedure, patients who had received continuous infusions had a factor level of greater than 90%; those who had received intermittent replacement had levels of greater than 50%. After discharge, the patients were treated with regular infusion of the deficient factor for 15 days. CONCLUSIONS: With adequate preoperative and post-procedure monitoring of clotting factors, meticulous attention to hemostasis during sphincterotomy, careful post-procedure monitoring, and timely replacement therapy, patients with hemophilia can undergo endoscopic sphincterotomy without bleeding complications.     

Aptamer ARC19499 mediates a procoagulant hemostatic effect by inhibiting tissue factor pathway inhibitor

Hemophilia A and B are caused by deficiencies in coagulation factor VIII (FVIII) and factor IX, respectively, resulting in deficient blood coagulation via the intrinsic pathway. The extrinsic coagulation pathway, mediated by factor VIIa and tissue factor (TF), remains intact but is negatively regulated by tissue factor pathway inhibitor (TFPI), which inhibits both factor VIIa and its product, factor Xa. This inhibition limits clot initiation via the extrinsic pathway, whereas factor deficiency in hemophilia limits clot propagation via the intrinsic pathway. ARC19499 is an aptamer that inhibits TFPI, thereby enabling clot initiation and propagation via the extrinsic pathway. The core aptamer binds tightly and specifically to TFPI. ARC19499 blocks TFPI inhibition of both factor Xa and the TF/factor VIIa complex. ARC19499 corrects thrombin generation in hemophilia A and B plasma and restores clotting in FVIII-neutralized whole blood. In the present study, using a monkey model of hemophilia, FVIII neutralization resulted in prolonged clotting times as measured by thromboelastography and prolonged saphenous-vein bleeding times, which are consistent with FVIII deficiency. ARC19499 restored thromboelastography clotting times to baseline levels and corrected bleeding times. These results demonstrate that ARC19499 inhibition of TFPI may be an effective alternative to current treatments of bleeding associated with hemophilia.     

Longitudinal changes in serum HBV DNA levels and predictors of progression during the natural course of HBeAg-negative chronic hepatitis B virus infection

Summary.  We evaluated the longitudinal changes of viraemia and predictors of progression in a prospectively followed cohort of 150 untreated patients with HBeAg-negative chronic hepatitis B virus (HBV) infection. According to the first year of follow-up, 85 patients were classified into inactive carrier state and 65 into chronic hepatitis B (CHB). Serum HBV DNA levels were determined at baseline in all patients, at year-1 in carriers or last pretherapy visit in CHB patients and during alanine aminotransferase (ALT) elevations in carriers progressing to CHB. HBV DNA levels at any occasion were ≥80, ≥2000 or ≥20 000 IU/mL in 81%, 23% or 0% of carriers and 100%, 95% or 83% of CHB patients. The cumulative progression rate from carrier to CHB was 11%, 16%, 24% at 2-, 3-, 4 years and was independently associated with higher baseline ALT (always within traditional normal range) and baseline HBV DNA ≥2000 or ≥5000 IU/mL. In 12 carriers progressed to CHB, HBV DNA increased by >1 log₁₀ IU/mL. During 7.5 months of median follow-up, HBV DNA change ≥1 log₁₀ IU/mL was observed in 49% of CHB patients. In conclusion, serum HBV DNA levels are detectable in the majority of inactive HBV carriers exceeding 2000 IU/mL in only 23% and 20 000 IU/mL in none of them. Carriers have approximately 15% 3-year risk of progression to CHB, which is associated with higher baseline ALT and viraemia ≥2000–5000 IU/mL, and thus should be closely followed. Approximately 20% of HBeAg-negative CHB patients have HBV DNA <20 000 IU/mL with fluctuations >1 log₁₀ occurring in many of them.     

Primary postpartum haemorrhage in women with von Willebrand disease or carriership of haemophilia despite specialised care: a retrospective survey

Pregnant women with bleeding disorders require specialised peripartum care to prevent postpartum haemorrhage (PPH). If third trimester coagulation factor levels are <0.50 IU mL^?1, prophylactic treatment is indicated and administered according to international guidelines. However, optimal dose and duration are unknown and bleeding may still occur. The aim of this study was to investigate the outcome in women with von Willebrand disease (VWD) or haemophilia carriership treated according to current practice guidelines. From the period 2002–2011, 185 deliveries in 154 VWD women or haemophilia carriers were retrospectively included. Data on blood loss, bleeding disorder characteristics and obstetric risk factors were obtained. The outcome was primary PPH, defined as blood loss ≥500 mL within 24 h postpartum and severe PPH as blood loss ≥1000 mL. Primary PPH was observed in 62 deliveries (34%), 14 (8%) of which resulted in severe PPH. In 26 deliveries prophylactic treatment was administered due to factor levels below the 0.50 IU mL^?1 cut‐off in the third trimester, 14 of which (54%) were complicated by PPH. We found an increased PPH risk in deliveries given prophylactic treatment compared with deliveries without (OR 2.7, 95% CI 1.2–6.3). In conclusion, PPH incidence was highest in deliveries with the lowest factor levels in the third trimester. Currently, delivery outcome in women with bleeding disorders is unsatisfactory, given the high PPH incidence despite specialised care. Future studies are required to optimise management of deliveries in this patient population.     

Hemorrhagic diathesis in a carrier of hemophilia B.

A carrier of hemophilia B was found to have an unusually low factor IX level of 13 per cent. Her history of previous bleeding and the hospital course following elective dental extractions were consistent with a mild hemorrhagic diathesis. The patient is a member of a rare kindred of hemophiliacs. The mean level of factor IX in 12 carriers in this kindred was 42 per cent, with a range of 13 to 100 per cent. This patient represents the sixth reported case in which a female carrier of factor IX deficiency was symptomatic.     

Detection of hemophilia A carriers using intragenic factor VIII:C DNA polymorphisms

A DNA polymorphism for an Xbal site in intron 22 of the human factor VIII:C gene extends the utility of DNA methods for carrier detection in families segregating for hemophilia A. While the DNA polymorphism detected by a BclI site in intron 18 of the factor VIII:C gene was informative for 41% of females studied, the BglI/intron 25 polymorphism provided no additional information because of apparent linkage disequilibrium. In contrast, the Xbal intron 22 polymorphism was useful in 53% of women who were uninformative (homozygous) for either the BclI or BglI polymorphisms. Using the BclI/intron 18 and Xbal/intron 22 intragenic polymorphisms, we could provide highly accurate information for 68% of women we studied who were at risk for carriership. The carrier status of the remaining 32% could be determined utilizing the closely linked Taql/St14 DNA polymorphism.     

The use of continuous infusion of factor concentrates in the treatment of hemophilia

Bolus infusion of clotting factor concentrates remains the most common approach to the treatment or prevention of bleeding in patients with hemophilia. Although successful use of continuous infusion of such concentrates has been reported by several groups, this alternative treatment method has not achieved widespread popularity. We report here our experience in one hemophilia center with the use of continuous infusion of factor VIII and factor IX concentrates in 13 patients, 11 with hemophilia A, and 2 with hemophilia B. All patients were treated successfully for bleeding episodes (e.g., hemarthroses, intracranial, or gastrointestinal bleeding) or for surgical procedures (appendectomy, thoracotomy, etc.). Three patients with low titer factor VIII inhibitors were treated successfully with constant infusion therapy, requiring a mean dose of factor VIII concentrate 2.3 fold (8.20 u/kg/h) higher than that of the patients without inhibitors (3.63 u/kg/h) to maintain a circulating plasma level of factor VIII of 1 u/ml. The use of constant infusion of clotting factor concentrates is safe, efficacious, and more convenient than bolus therapy of factor concentrates and should be considered for hospitalized hemophilia patients requiring replacement therapy.