Prevalence, biological phenotype and genotype in moderate/mild hemophilia A with discrepancy between one-stage and chromogenic factor VIII activity

BACKGROUND

In most laboratories, the severity of hemophilia A is assessed by the factor VIII activity (FVIII:C) one-stage assay. However, comparisons of these results with those of two-stage assays can reveal discrepancies and suggest misdiagnosis.

PATIENTS/METHODS

In this monocentric study, we measured FVIII:C with two methods (one-stage chronometric and chromogenic assays) in 307 (173 families) patients with moderate/mild hemophilia A. To compare results, we used a chronometric/chromogenic ratio. Discrepancy was defined as a ratio < 0.5 or > 1.5. We studied their putative involvement at known FVIII functional sites, their interspecies conservation status, and their spatial position within the FVIII structure.

RESULTS

Thirty-six patients from 17 families exhibited a discrepancy between the two assays: 12 (6.9%) families had a low ratio (< 0.5), and five (2.9%) families had a high ratio (> 1.5). Qualitative deficiency was diagnosed in about 16% of the families. Molecular studies were performed in 15 of these 17 families, resulting in each case in the identification of missense mutations, including three novel mutations. We were further able to propose a pathophysiologic explanation.

CONCLUSIONS

In this monocentric study, we have demonstrated a discrepancy between FVIII:C assay results in 10% of families with moderate/mild hemophilia A. The prevalence of 'inverse' discrepancy (i.e. low chronometric/chromogenic ratio) is high as compared with previous reports. We suggest that both FVIII:C assays are recommended in patients with moderate/mild hemophilia A for a complete biological phenotype. This could also improve our knowledge of the FVIII structure-function relationships.

[Tailless tenrec (Tenrec ecaudatus): natural maintenance host of leptospires?]

In order to know if the Tailless tenrec (Tenrec ecaudatus), endemic insectivorous mammal of Madagascar and present only on Indian Ocean islands, is a natural maintenance host of leptospires carrier in La Reunion, we conducted a research of anti-leptospire antibodies by microagglutination test in 37 individuals. 81.1% of serums tested were positive, (> 1/50) with the highest titers for the Icteroharmorrhagiae serogroup. So, in la Reunion, the Tailless tenrec can be suspected of being a reservoir of leptospires. A more detailed study should confirm or not this hypothesis and should possibly quantify its importance.

Mild hemophilia A with factor VIII assay discrepancy: using thrombin generation assay to assess the bleeding phenotype

INTRODUCTION

In some patients with mild hemophilia A, there are discrepancies between 1-stage (1-st) and 2-stage (2-st) factor VIII (FVIII) clotting assays, and also chromogenic assays for FVIII activity (FVIII:C). We examined whether thrombography could provide a better evaluation of the hemostatic status of these patients.

METHODS

Two families with such discrepancies and markedly contrasting clinical histories were studied. Family X had no serious bleedings, in contrast to family Y. Sixty-one moderate/mild hemophiliacs without discrepancy and 15 healthy subjects served as controls. Calibrated automated thrombography was performed with platelet-rich plasma after one freeze-thawing cycle and low tissue factor concentration.

RESULTS

The chromogenic FVIII:C levels were higher (0.90 +/- 0.15 and 0.47 +/- 0.13 IU mL(-1)) than the 1-st clotting ones (0.14 +/- 0.05 and 0.10 +/- 0.05 IU mL(-1)) in family X and Y, respectively (P < 0.001). Mean endogenous thrombin potential (ETP) was 1579 +/- 359 nM min(-1) and 1060 +/- 450 for healthy controls and hemophilic controls, respectively. For members of family X, the ETP values were 1188, 1317 and 2277 nM min(-1), whereas for those of family Y they ranged from 447 to 1122 nM min(-1). Two novel missense point mutations were evidenced: p.Ile369Thr in family X and p.Phe2127Ser in family Y. In family X, we postulate that the mutation is responsible for a delayed but non-deleterious FVIII activation.

CONCLUSIONS

Our results suggest that the hemostatic phenotype assessed by thrombography may be clinically relevant in moderate/mild hemophilic patients with discrepant FVIII:C results.

Factor VIII recovery after a single infusion of recalibrated ReFacto�in 14 severe haemophilia A patients

A recent multicentre collaborative study showed higher estimates of ReFacto potency when assayed with ReFacto Laboratory Standard(TM) (RLS) in comparison when standards consisting of full-length factor VIII (FVIII) were used. The RLS was hence recalibrated, leading to a 20% increase in the amount of ReFacto per vial without change in the labelled potency. The primary objective of this study was to determine the incremental and in vivo recovery of the recalibrated ReFacto in patients with severe haemophilia A. Fourteen male severe haemophilia A patients (FVIII < 1 IU dL(-1)) with a cumulative previous exposure days to any FVIII product >150 were administered an intravenous infusion 50 +/- 5 IU kg(-1) of ReFacto over a 5-min period. Blood samples were collected before infusion and after 15, 30 and 60 min. FVIII clotting activity (FVIII:C) was assessed in a central laboratory by the chromogenic substrate assay. After ReFacto infusion, peak FVIII:C was obtained within 15 min for 10 patients and within 30 min for the remaining four. Mean FVIII:C at peak was 117.7 +/- 17.3 IU dL(-1). Mean incremental recovery was 2.22 +/- 0.27 IU dL(-1) per IU kg(-1) while mean in vivo recovery was 105.9 +/- 14.6%. One patient reported three mild adverse events rated as 'unrelated' to the study drug. FVIII recovery after recalibrated ReFacto infusion falls within the expected range and is similar to the values reported for other FVIII concentrates.

Molecular basis of severe factor XI deficiency in seven families from the west of France. Seven novel mutations, including an ancient Q88X mutation

Inherited factor (F)XI deficiency is a rare disorder in the general population, though it is commonly found in individuals of Ashkenazi Jewish ancestry. In particular, two mutations--a stop mutation (type II) and a missense mutation (type III)--which are responsible for FXI deficiency, predominate. The bleeding tendency associated with plasma FXI deficiency in patients is variable, with approximately 50% of patients exhibiting excessive post-traumatic or postsurgical bleeding. In this study, we identified the molecular basis of FXI deficiency in 10 patients belonging to six unrelated families of the Nantes area in France and one family of Lebanese origin. As in Ashkenazi Jewish or in French Basque patients, we have identified a new ancient mutation in exon 4 resulting in Q88X, specific to patients from Nantes, that can result in a severely truncated polypeptide. Homozygous Q88X was found in a severely affected patient with an inhibitor to FXI and in three other unrelated families, either as homozygous, heterozygous or compound heterozygous states. Other identified mutations are two nonsense mutations in the FXI gene, in exon 7 and 15, resulting in R210X and C581X, respectively, which were identified in three families. A novel insertion in exon 3 (nucleotide 137 + G), which causes a stop codon, was characterized. Finally, sequence analysis of all 15 exons of the FXI gene revealed three missense mutations resulting in G336R and G350A (exon 10) and T575M (exon 15). Two mutations (T575M and G350A) with discrepant antigen and functional values are particularly interesting because most of the described mutations are associated with the absence of secreted protein.

Therapeutic monitoring of von Willebrand disease: interest and limits of a platelet function analyser at high shear rates

We have evaluated the position of the Platelet Function Analyzer PFA-100TM in the management of 41 patients with von Willebrand disease (VWD) receiving either desmopressin (23 patients with type 1, five with type 2M, three with type 2A and three with type 2B) or von Willebrand factor (VWF) concentrates (four patients with type 3, two with type 2M 'type B', two with type 2A and one type 1 'platelet low'). In all patients the following were studied before and 30 min after infusion of desmopressin and/or VWF concentrates: VWF ristocetin cofactor activity (VWFRCo), bleeding time (BT) and closure time with the PFA-100 using ADP (CT-ADP) as well as epinephrine (CT-Epi) cartridges. After the infusion of desmopressin, the CT was modified in the same way as the VWFRCo levels, being always normalized in patients with type 1 and not constantly corrected in those with type 2. Thus, our results indicated that the measurement of the CT enabled a quick and accurate evaluation of the response to desmopressin which, in fact, measured the releasable VWF cellular compartment containing the highly multimerized forms of VWF. For patients with type 2 or 3 VWD who were non-responsive to desmopressin, VWF concentrates corrected the VWFRCo defect but not the CT as none of these patients had a normal platelet VWF content and the VWF concentrates did not contain the ultralarge VWF multimers. In conclusion, the very high shear conditions in the PFA-100 make it very sensitive to the contribution of platelet VWF and to the ultralarge VWF multimers, indicating that the evaluation of the CT is a very simple and rapid tool to discriminate between good and non-responders to desmopressin.

[Tiopronin in 69 cases of rheumatoid polyarthritis treated earlier with D-penicillamine]

This study concerns 69 patients with rheumatoid arthritis (RA) and having received successively D-penicillamine (DP) then, after a mean period of 2 years, tiopronin (TP) at a daily dose of 1,500 mg. TP demonstrated an as frequent, as marked, and as prolonged effectiveness as that of DP. 28 patients are still under TP treatment, with a mean length of treatment of 43.7 months. The rate of effectiveness of TP was similar, whether or not the response to DP was favorable: 64.1 and 64.3 p. cent respectively; 72.4 p. cent of the 29 cases which did not respond to DP, responded favorably to TP. The manifestations of intolerance to TP were similar in nature (including the first reported case of obstructive bronchiolitis) and frequency to those observed with DP. There were only a few manifestations of crossed intolerance: the rate of TP discontinuation because of intolerance was the same, whether the DP was well tolerated (29.6%) or discontinued because of poor tolerance (30%). The same undesirable effect was only observed in 4 cases: one case of pemphigus, another case of toxic dermatitis, 2 proteinurias. This study confirms that TP represents a new, major long-term treatment of RA and demonstrates that this very product is an excellent take over medication.