Genetic predisposition to bleeding during oral anticoagulant therapy: evidence for common founder mutations (FIXVal-10 and FIXThr-10) and an independent CpG hotspot mutation (FIXThr-10).

The recent discovery of five patients with coumarin sensitive FIX-variants due to a missense mutation in the FIX propeptide, either Ala-10Val or Ala-10Thr, has highlighted a novel type of genetic predisposition to bleeding during oral anticoagulant therapy (OAT). In the present study, we report six additional patients with such FIX variants. Haplotype analysis of FIX polymorphisms revealed a founder effect in the five German and Swiss patients with the Val-10 variant. Also, four Thr-10 variants detected in Germany, Switzerland and Great Britain derived from a common founder. Two Thr-10 variants from USA showed an independent de novo origin at a CpG dinucleotide that in general represents a mutation hotspot. These findings implicate the existence of additional subjects with corresponding variants in the populations of various countries. Even though the rare occurrence of these variants does not justify a general aPTT screening during OAT, it is recommended to monitor each bleeding event during OAT in males in order to exclude a genetic predisposition to bleeding by means of the following testing strategy: a) aPTT-testing in each bleeding complication of male patients during OAT, b) if aPTT is disproportionately prolonged, determination of FIX:C, and c) if FIX:C is disproportionately decreased as compared to FII:C, FVII:C and FX:C, sequencing of exon 2 of the FIX gene. This strategy will provide a cost-effective and safe procedure to identify patients that carry the FIX variants. Moreover, such a strategy accumulates data about the prevalence of these FIX mutations in a given population.

No clinically relevant effect of lornoxicam intake on acenocoumarol pharmacokinetics and pharmacodynamics.

OBJECTIVE: To investigate the effect of lornoxicam co-administration on acenocoumarol pharmacokinetics and pharmacodynamics. METHODS: In an open crossover study, six healthy male volunteers received racemic acenocoumarol (10 mg) orally without/with lornoxicam co-administration (8 mg twice daily). RESULTS: The median (range) areas under the concentration-time curve (AUC) for (R)-acenocoumarol were 3458 (3035-7312) microg x h 1(-1) in the absence of and 3667 (2907-7741) microg x h 1(-1) in the presence of lornoxicam. The corresponding values for (S)-acenocoumarol were 479 (381-853) microg x h 1(-1) and 612 (425-1241) microg x h 1(-1). The differences were not statistically significant. Lornoxicam co-administration did not influence the free fractions or acenocoumarol's effect on factor II and VII activities. Simulations based on the results of a model-based analysis predicted that in the case of lornoxicam co-administration, the factor VII activity of a person in steady-state at 26% will remain between 14% and 32%. CONCLUSION: Co-administration of lornoxicam at the upper limit of recommended doses does not alter the pharmocokinetics of the clinically relevant (R)-acenocoumarol or the anticoagulant activity of acenocoumarol. These data clearly differ from the results of previous studies, which showed clinically relevant influences of lornoxicam on warfarin kinetics and of piroxicam on acenocoumarol kinetics.

Opposite effects of lornoxicam co-administration on phenprocoumon pharmacokinetics and pharmacodynamics.

OBJECTIVE: To investigate the effect of co-administration of the non-steroidal anti-inflammatory drug (NSAID) lornoxicam on the pharmacokinetics of (R)- and (S)-phenprocoumon and their effect on factor II and VII activities. METHODS: Six healthy male volunteers completed an open crossover study. Plasma concentrations of (R)- and (S)-phenprocoumon and activities of coagulation factors II and VII were measured after a single oral dose of 9 mg phenprocoumon racemate. In the second session, lornoxicam administration was started 3 days before phenprocoumon administration and continued twice daily until the last blood sample was drawn. RESULTS: Lornoxicam co-administration resulted in a statistically significant increase of the area under the concentration-time curve (AUC) of the more potent (S)-isomer of phenprocoumon from a median value of 100 (range 68-146) mg x h x 1(-1) to 124 (92-239) mg x h x 1(-1). For the (R)-isomer, the AUC increase from 96 (70-142) mg x h x 1(-1) in the absence to 108 (75-155) mg x h x 1(-1) in the presence of lornoxicam was not statistically significant. In a model-based analysis, an increase of (S)-phenprocoumon and (R)-phenprocoumon bioavailability of 14% [95% CI (9%, 19%)] and 6% (2%, 10%) and a decrease of their clearances by 15% (8%, 21%) and 6% (0%, 13%) was obtained. Lornoxicam co-administration did not influence the free fractions of (R)- or (S)-phenprocoumon. Contrary to what was expected from the changes in pharmacokinetics, a statistically significant decrease in the effect of phenprocoumon on factor II and VII activity was observed for the sessions with lornoxicam co-administration. For factor VII, lornoxicam was found to increase the concentration causing half-maximal effect (C50) of phenprocoumon by 70% [95% CI (38%, 111%)]. CONCLUSION: Co-administration of lornoxicam at the upper limit of recommended doses mainly altered the pharmacokinetics of the more potent (S)-isomer and to a lesser degree those of (R)-phenprocoumon. Despite these changes in pharmacokinetics, a decrease of the effect on factor II and VII activity was observed. These results suggest that in the case of lornoxicam co-administration in a patient treated with phenprocoumon the prothrombin time should be monitored closely.

Antibodies against platelet glycoproteins and antiphospholipid antibodies in autoimmune thrombocytopenia.

Autoantibodies against platelet glycoproteins (anti-GP) are found in the majority of patients with autoimmune thrombocytopenia (AITP) as well as in thrombocytopenia associated with systemic lupus erythematosus (SLE). Some of these patients may have anti-phospholipid antibodies (anti-PL). To evaluate the pathogenetic significance of anti-PL and anti-GP antibodies in AITP and SLE patients, we investigated anti-cardiolipin (anti-CL), anti-phosphatidylserine (anti-PS) and anti-GP antibodies (anti-GPIIb-IIIa and anti-GPIb-IX) in 71 patients with AITP and 3 thrombocytopenic patients with SLE. Anti-GP antibodies were detected in 52 (70%) patients. Fifty-six (73%) patients showed anti-PL antibodies. Seven patients (6 AITP, 1 SLE) with both anti-GPIIb-IIIa and IgG anti-PL antibodies were followed during treatment with corticosteroids. Antibodies were measured before treatment and at the time of platelet-peak. Anti-GPIIb-IIIa antibodies decreased in all or became undetectable in five. In contrast, IgG anti-PS and IgG anti-CL antibodies decreased only moderately or remained positive. Adsorption experiments, using gelfiltered platelets, erythrocyte (Ec)-inside-out-vesicles and purified GPIIb-IIIa, showed that anti-GP and anti-PL antibodies have distinct specificities and do not crossreact. We conclude that anti-PL and anti-GP antibodies may be present simultaneously in some patients with immune mediated thrombocytopenia. Although anti-PS as well as anti-CL antibodies may be responsible for thrombocytopenia, we speculate that anti-GPIIb-IIIa antibodies are more related to the severity of thrombocytopenia.

Is heparin therapy necessary in CAPD peritonitis?

OBJECTIVE: Heparin therapy in continuous ambulatory peritoneal dialysis (CAPD) peritonitis seems well established; it is costly due to the necessity of hospitalization. There are no clinical studies that show a benefit of such a treatment. The aim of this study was to investigate whether heparin therapy in CAPD peritonitis is necessary. DESIGN AND PATIENTS: 194 samples of peritoneal dialysates were collected from 17 patients over a period of 24 months. Samples were subdivided into three groups: those without peritonitis (< 100 leukocytes/microL), those with mild peritonitis (100-499 leukocytes/microL), and those with severe peritonitis (> or = 500 leukocytes/microL). MEASUREMENTS: The number of leukocytes per microL dialysate and total protein concentrations were determined. Furthermore, dialysate concentrations of thrombin-antithrombin III- (TAT-) complexes (indicator of thrombin formation), D-dimers (indicator of fibrinolysis), and plasminogen activator inhibitor 1 (PAI-1) were measured. RESULTS: The dialysate protein concentration progressively increased from no peritonitis to mild and severe inflammation. In parallel, dialysate TAT-complex and D-dimer concentrations increased. Thrombin-antithrombin III-complex and D-dimer concentrations correlated strongly in 179 cases (r = 0.76; 62 samples showing peritonitis, 117 samples with no evidence of peritonitis). In the remaining 15 samples of 3 patients, high PAI-1 levels (> 40 ng/mL) and low D-dimer concentrations were found. Eleven of the 15 samples showed evidence of peritonitis. In these 11 samples with evidence of peritonitis, high levels of TAT-complexes were detected, while D-dimer concentrations were found to be very low, pointing to a blocked fibrinolysis. The PAI-1 levels were not related to leukocyte counts or protein concentrations in the dialysates. CONCLUSIONS: Based on our findings, the routine intraperitoneal administration of heparin in CAPD peritonitis is not necessary. In rare cases an imbalance between coagulation and fibrinolysis due to high PAI-1 levels exists (15 of 194 dialysate samples, 11 of the 15 samples showing peritonitis). These cases--which do require heparinization--can be identified by demonstrating low D-dimer levels in CAPD dialysate at times of peritonitis.

Quantitation of platelet-specific autoantibodies in platelet eluates of ITP patients measured by a novel ELISA using the purified glycoprotein complexes GPIIb/IIIa and GPIb/IX as antigens.

Immune thrombocytopenic purpura (ITP) is a disorder caused by anti-platelet autoantibodies (Ab), most of which are directed against epitopes on platelet membrane glycoprotein complexes GPIIb/IIIa and GPIb/IX. To detect platelet Ab, reliable techniques, such as MAIPA or immunobead assay, have been developed. They all achieve their selective specificity by the use of monoclonal antibodies (MoAb) against defined glycoproteins of the platelet membrane. In order to determine the most frequent Ab-specificities, a novel enzyme-linked immunosorbent assay, named platelet-glycoprotein-ELISA (P-GP-ELISA), has been developed. It uses purified GPIIb/IIIa and GPIb/IX complexes, respectively, as antigens and enables determination of platelet-associated as well as circulating Ab (IgG, IgM). MoAbs are not required and therefore there is no risk of competition between MoAb and Ab. Levels of Ab in patients with the clinical diagnosis of an idiopathic thrombocytopenic purpura were analysed. 92.7% (76/82) platelet eluates with significantly increased levels of Ab against at least one of the glycoproteins were found, whereas no sample from healthy volunteers (0/37) gave a positive result, pointing to a high sensitivity and specificity of the test system. Since its application is also easy and quick, P-GP-ELISA should facilitate detection of Ab against platelet membrane proteins in routine determinations.

[May-Hegglin anomaly: further studies on thrombocyte dysfunction]. / May-Hegglin-Anomalie: ergänzende Untersuchungen zur Frage der Thrombozyten-Funktionsstörung.

The May-Hegglin anomaly is an extremely rare, autosomal dominant inherited disorder characterized by alterations in white cells and in blood platelets. The granulocytes show basophilic inclusion bodies of no clinical importance. Usually moderate thrombocytopenia with variable platelet size, including giant platelets, is also found. Clinically a mild hemorrhagic diathesis may occur. We report on a so far asymptomatic patient from the second family described by Hegglin et al. in 1964 [1] who had to be treated for repeated life-threatening bleedings. A moderate prolongation of bleeding time was found, corresponding to the reduced platelet count; platelet aggregation induced by ADP, collagen, ristocetin or arachidonic acid was not impaired. Therefore, there is at present no evidence of a congenital platelet function defect in the May-Hegglin anomaly. The bleeding time improved temporarily in our patient on administration of DDAVP (Minirin); platelet substitution is indicated in special situations only.

[Factor XI deficiency: do patients with hemorrhagic diathesis also have hemostasis defects?]. / Faktor-XI-Mangel: Weisen Patienten mit Blutungsneigung zusätzliche Hämostasedefekte auf?

It is well known that the extent of bleeding in patients with a deficiency of factor XI does not parallel the residual factor activity. Therefore, additional hemostatic aspects must be taken into consideration. 27 patients of 18 different families--6 with severe (FXI < 0.01 to 0.09 U/ml) and 21 with moderate (FXI 0.20 to 0.252 U/ml) factor XI deficiency--were reinvestigated regarding hemostasis including bleeding time and platelet function. 16 had an enhanced bleeding tendency, while the others--including 3 with severe FXI deficiency of < 0.01 U/ml--never suffered from bleeding complications despite delicate surgery in some. All 16 of the symptomatic patients had, besides the reduction of factor XI activity to various extents, an additional hemostatic defect: 3 had a moderate alpha/delta storage pool detect of the platelets, 11 a platelet anomaly mainly characterized by reduced ADP aggregation and 2 an isolated prolonged bleeding time of unknown cause. Synthesis of platelet thromboxane was unimpaired in all patients as tested by formation of malondialdehyde after stimulation with N-ethyl maleimide. Hence, in patients with a known factor XI deficiency diagnostic and prophylactic measures before surgery should concentrate on such additional findings. Preoperative administration of desmopressin, and not replacement of factor XI, will be the treatment of choice in these cases.

Quantitative and qualitative analysis of platelet GPIb and von Willebrand factor in liver cirrhosis.

Numerous abnormalities of plasmatic coagulation and platelet function may contribute to the bleeding in liver cirrhosis with a defective platelet-von Willebrand factor interaction being a potential mechanism. To analyze GPIb and von Willebrand factor in cirrhosis, we quantified the number of GPIb molecules on the platelet surface by flow cytometry, assessed the total (and indirectly the internal) pool of GPIb by ELISA and measured the circulating amount of glycocalicin in plasma as a measure of proteolytic activity and platelet turnover. Von Willebrand factor was characterized by ELISA, by its ristocetin-cofactor activity and by multimer analysis. Botrocetin-induced agglutination was used for functional analysis. The data from 8 well-characterized cirrhosis patients indicate that total GPIb is insignificantly increased to 46,000 +/- 5,000 molecules/P (normal: 39,500 +/- 2,000 [SEM]), surface-GPIb is normal with some variability and that the glycocalicin levels are 2-3 times higher than would be expected from the platelet count (= 100 +/- 5 x 10(9)/l). Von Willebrand factor antigen levels and activity were 400-500% of normal with a 22% reduction of the high molecular weight multimers. A significant hyperagglutination response to botrocetin was observed with platelets from both patients and controls using patient plasma as a source of von Willebrand factor. In conclusion, a hyperresponsiveness rather than a defective platelet-von Willebrand factor interaction can be observed in cirrhosis which may compensate for other hemostatic problems and appears to be mediated primarily by increased levels of von Willebrand factor.

[Recombinant activated Factor VII (Novoseven Novo Nordisk) for hemostasis in acquired Factor VIII-inhibitor hemophilia]. / Rekombinanter aktivierter Faktor VII (Novoseven Novo Nordisk) zur Blutstillung bei erworbener Hemmkörper-Hämophilie.

One life threatening mediastinal hemorrhage and two limb threatening hemorrhages, one in the retroperitoneal and thigh muscles and the other in the back of the hand requiring surgical evacuation, were treated with recombinant activated factor VII concentrate (rFVIIa; Novoseven Novó Nordisk) in a patient with a postpartum acquired inhibitor against factor VIII. High dose activated prothrombin complex concentrate (Feiba sTIM4 Immuno), repeatedly administered, had proven to be ineffective; porcine factor VIII concentrate (Hyate C Porton) had become ineffective due to a rise in inhibitor titers against human and porcine factor VIII as well. 90 micrograms rFVIIa per kg body weight was administered as an i.v. bolus injection every 2-3.5 hours. The treatment periods were 22.5 days in the mediastinal and 11 days in each of the two other hemorrhages. Hemostasis was promptly achieved and maintained. All manipulations (bone marrow biopsy, surgical evacuation of the hematoma, change of venous access, withdrawal of drains, change of dressings) were done immediately after rFVIIa administration, without bleeding complications. There were no side effects despite the high dose, frequent and long lasting treatment with a total of 234 x 4.8 and 46 x 3.6 mg rFVIIa. The concentrate was well tolerated, there were no signs of systemic activation of coagulation, either in the coagulation test results or clinically, in spite of patient's factor VII levels up to 60 U/mL and prothrombin times around 6 s. No inhibitors against patient's factor VII, induced by rFVIIa, were detected. Due to its extrinsic factor VIII bypass effect, rFVIIa led to excellent hemostasis even with inhibitor titers of 376 Bethesda units against human and 44 against porcine factor VIII. Nevertheless, immunosuppressive treatment with cyclophosphamide and prednisone was performed, with prompt decrease of the inhibitor titer.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergen exposure in acute asthma causes the release of platelet-activating factor (PAF) as demonstrated by the desensitization of platelets to PAF.

Platelet-activating factor (PAF) is released in IgE-mediated allergic diseases. The normal level, the method of its determination and its clinical importance are subject of controversy. We hypothesized that a functional assay could help to better analyze the actual concentrations in vivo because PAF may be released locally and is short-lived. An assay to detect PAF by the desensitized state of human platelets exposed to PAF in vitro or ex vivo was developed: We analyzed the synergistic platelet response to dual agonist stimulation at extraordinarily low doses (collagen 0.10 microgram/ml and PAF 2.5 x 10(-8) M) in aggregation and release reaction and its absence after previous exposure to PAF at concentrations between 5 x 10(-9) and 5 x 10(-11) M in vitro. The same test was then applied to examine the platelets from patients with IgE-mediated allergic asthma before and after inhalation of the specific allergen (inhalative provocation test; a reduction of the FEV1 by > 15% was considered positive). The lack of a synergistic response to collagen with PAF was found after preincubation of the platelets with 5 x 10(-9) M PAF and a reduction of +/- 50% with 5 x 10(-10) M in vitro. A significant reduction of the aggregation response (-56 +/- 18%) and of the release of beta-thromboglobulin (-75 +/- 24%) was found in 6 patients with a positive inhalative provocation test but not in 3 patients with a negative response.(ABSTRACT TRUNCATED AT 250 WORDS)

Coagulation patterns during deheparinization with immobilized polycation.

Reversal of systemic heparinization with protamine is problematic during perfusion with heparin surface coated devices because protamine reacts with both circulating and surface bound heparin. Hence, the development of a deheparinization device allowing for ex vivo heparin absorption by the means of an immobilized polycation is of prime interest for a number of indications. To assess the coagulation patterns during ex vivo deheparinization, a heparin surface coated venovenous pump loop including a plasma separator with immobilized polycation was studied in a bovine model (n = 6, body weight 71 +/- 5 kg). After systemic heparinization with 300 IU of heparin/kg body weight, spontaneous evolution (control) of coagulation parameters was compared to ex vivo deheparinization with a mean pump flow of 500 ml/min. No device failure occurred during the procedures and all plasma separators remained patent. These baseline levels were measured for control versus ex vivo deheparinization: activated coagulation time 158 +/- 6 sec (161 +/- 4 sec: NS), antithrombin III 101 +/- 5% (108 +/- 8%: NS), fibrinopeptide A 3.4 +/- 1.7 ng/ml (4 +/- 1.7 ng/ml: NS). After heparin application mean activated coagulation time was longer than 1000 sec in both groups. Sixty minutes later, the activated coagulation time was 757 +/- 43 sec (184 +/- 5 sec: P < 0.05), antithrombin III was 96 +/- 12% (99 +/- 2%: NS), and fibrinopeptide A was 2.7 +/- 0.7 ng/ml (9.5 +/- 3.5 ng/ml: P < 0.05). It is concluded that ex vivo deheparinization resulted in significant acceleration of activated coagulation time normalization. Fibrinopeptide A production in the group with ex vivo deheparinization appeared to be higher. As antithrombin III levels were close to normal in both groups, allowing for adequate function of circulating as well as surface bound heparin, and the coagulation process was blocked by significant heparin levels in the control group, the difference for FPA may be due to activation of the coagulation process in the surgical field (sternotomy).

[Is the activated partial thromboplastin time suitable for monitoring of thrombosis therapy with high-dose standard heparin?]. / Ist die aktivierte partielle Thromboplastinzeit (aPTT, PTT) zur Uberwachung der Thrombose-therapie mit hochdosiertem Standard-Heparin geeignet?

The activated partial thromboplastin time (aPTT, PTT) is widely used to monitor therapeutic anticoagulation with standard heparin. However, it has been known for some time that PTT reagents obtained from various manufacturers display different sensitivities to heparin--a fact which often is not taken into account. The study deals with the question whether the sensitivity of the PTT to heparin is additionally influenced by the decrease in the vitamin K-dependent coagulation factors such as occurs after starting oral anticoagulation (OAC). In in-vitro studies the reaction of the PTT was observed after addition of different amounts of heparin to normal plasma, to plasma taken after the start of OAC and during stable OAC. The results show that the PTT tends to be more sensitive to heparin as soon as oral anticoagulation is initiated. This phenomenon already occurs at an early stage of anticoagulant intake where only factor VII is markedly reduced but prothrombin concentration is still in an almost normal range and therefore a clinically sufficient effect of OAC is not to be expected. Identical results are obtained with plasma samples of heparin treated patients before and after the start of OAC; in addition, a scattering of the PTTs is obvious. This leads to overestimation of heparin concentrations and a consequent reduction of dosage at an early, still insufficient stage of OAC. In contrast, the thrombin time shows--independently of OAC--a good correlation to heparin concentrations. Therefore the thrombin time is more appropriate to monitor heparin therapy in the phase when oral anticoagulation is started.

[3-line response following long-term therapy of severe aplastic anemia using glycosylated rHuG-CSF: dysfunctional thrombocytes as early indication of a myelodysplastic syndrome]. / Dreilinien-Antwort nach Langzeittherapie einer schweren aplastischen Anämie mit glykosyliertem rHuG-CSF: dysfunktionelle Thrombozyten als Frühzeichen eines myelodysplastischen Syndroms.

We report on a patient with very severe aplastic anemia (SAA) unresponsive to immunosuppressive therapy (cyclosporine A, ATG). Because no HLA-identical family or unrelated donor could be found, a trial with recombinant human granulocyte stimulating factor (G-CSF) was started. This was followed by a rapid 3-lineage response with near-normal blood counts and transfusion independence. A similar response was obtained by 2 further G-CSF cycles which were given for relapsing SAA after G-CSF withdrawal. Following the third cycle, an acquired platelet function disorder was observed which preceded a myelodysplastic syndrome.

Functional characterization of a variant prekallikrein (PK Zürich).

The plasma of a 68-year-old man with cross reacting material (CRM)-positive prekallikrein (PK) deficiency was studied. PK clotting activity was < 0.01 U/ml, and PK antigen was 0.1 U/ml. No circulating anticoagulant against PK was detectable. The abnormal PK molecule, denoted as prekallikrein Zürich, was partially characterized by immunological and functional studies on the propositus' plasma. Immunoblotting analysis showed the abnormal PK being a single chain molecule of the same M(r) (80 kDa) as normal PK. Dextran sulfate activation of the propositus' plasma did not lead to proteolytic cleavage of the variant PK molecule, in contrast to dextran sulfate activation of a mixture of 1 volume normal plasma and 9 volumes CRM-negative PK deficient plasma. Agarose gel electrophoresis followed by immunoblotting demonstrated that PK Zürich was complexed with high molecular weight kininogen similarly to PK in normal plasma. Incubation of the propositus' plasma with purified beta-FXIIa resulted in impaired cleavage of PK Zürich when compared with PK hydrolysis in a mixture of 10% normal plasma and 90% CRM-negative PK deficient plasma. Moreover, proteolytically cleaved PK Zürich showed no enzymatic activity against factor XII and high molecular weight kininogen. These studies show that the functional defect of prekallikrein Zürich is due to an impaired cleavage by activated factor XII and probably the lack of enzymatic activity of the cleaved variant molecule.

Detection of missense mutations by single-strand conformational polymorphism (SSCP) analysis in five dysfunctional variants of coagulation factor VII.

Five unrelated subjects with dysfunctional coagulation factor VII (FVII) were studied in order to identify missense mutations affecting function. Exons 2 to 8 and the intron-exon junctions of their FVII genes were amplified from peripheral white blood cell DNA by PCR and screened by SSCP analysis. DNA fragments showing aberrant mobility were sequenced. The following mutations were identified: in case 1 (FVII:C < 1%, FVII:Ag 18%) a heterozygous A to G transition at nucleotide 8915 in exon 6 results in the amino acid substitution Lys-137 to Glu near the C-terminus of the FVIIa light chain; in case 2 (FVII:C 7%, FVII:Ag 47%) a heterozygous A to G transition at nucleotide 7834 in exon 5 results in the substitution of Gln-100 by Arg in the second EGF-like domain; in case 3 (FVII:C 20%, FVII:Ag 76%) a homozygous G to A transition at nucleotide position 6055 in exon 4 was detected resulting in substitution of Arg-79 by Gln in the first EGF-like domain; in case 5 (FVII:C 10%, FVII:Ag 52%) a heterozygous C to T transition at nucleotide position 6054 in exon 4 also results in the substitution of Arg79, but in this case it is replaced by Trp; case 4 (FVII:C < 1%, FVII:Ag 100%) was homozygous for a previously reported mutation (G to A) at nucleotide position 10715 in exon 8, substituting Gln for Arg at position 304 in the protease domain. Cases 1, 2 and 5 evidently have additional undetected mutations.

Autoantibodies against the platelet glycoproteins (GP) IIb/IIIa, Ia/IIa, and IV and partial deficiency in GPIV in a patient with a bleeding disorder and a defective platelet collagen interaction.

To evaluate the physiologic importance of the different collagen receptors on platelets, we screened 806 patients admitted to the hospital because of hemorrhagic diathesis for eventual laboratory evidence of a pathologic platelet collagen interaction, and found 5 patients with an isolated deficiency in collagen-induced platelet aggregation. Four of these five patients had a partial defect, one had a complete defect. The structural and functional analysis of the platelets from the patient with a complete defect showed a deficiency in glycoprotein (GP) IV and autoantibodies against GPIIb/IIIa, GPIa/IIa, and GPIV. Patient plasma had only a minimal effect on normal control platelets and Naka-negative platelets. The analyses of the defect in the patient and of the data in the literature suggest that a single defect may not result in clinical bleeding (GPIV-deficient patients do not bleed), but may become symptomatic in combination with another defect such as the autoantibodies against GPIa/IIa, GPIV, and/or GPIIb/IIIa, all of which are involved in platelet collagen interactions (three of four of our immune thrombocytopenic purpura patients with anti-GPIV and anti-GPIIb/IIIa autoantibodies had a bleeding disorder). We hypothesize that it is the synergism of two abnormalities that results in the defective function, a mechanism that is in agreement with earlier studies on platelet collagen interaction that suggests that a double defect in platelet collagen interactions is required to become clinically apparent.