Abnormalities in platelet function due to defects in the release reaction

Haemarthroses after total knee arthroplasty caused by an isolated platelet factor 3 availability defect

We present seven patients with recurrent haemarthroses after total knee arthroplasty, caused by an inherent platelet function defect. These patients developed painful knee swelling, persistent bleeding and/or wound breakdown, a platelet factor 3 availability defect being identified in all cases. Surgical exploration, with joint debridement, lavage and synovectomy, was performed in four patients who did not improve with conservative therapy. Histopathological examination of synovium revealed a focal synovial reaction with histiocytic infiltration, and occasional foreign-body giant cells. One patient required an early revision because of aseptic loosening of their tibial component. The condition was treated by single-donor platelet transfusions with good results. The diagnosis, management, and relevance of this disorder are discussed.

Clinico-haematological profile of isolated PF3 availability defect: therapeutic potential of soya bean--a pilot study

Isolated platelet factor 3 (PF3) availability defect has been observed to be a common platelet functional disorder (PFD) in the Department of Haematology, All India Institute of Medical Sciences, New Delhi, India. One hundred and thirty-two patients were diagnosed to have this defect based on the presence of reduced PF3 availability, normal platelet aggregation with ADP, collagen, adrenaline, ristocetin, and arachidonic acid and normal PF3 content. PF3 availability was evaluated by measurement of Russel viper venom time (RVVT) on the patient's platelet-rich plasma (PRP) after incubation with ADP for 20 min. An RVVT value >19.0 s was considered diagnostic of reduced PF3 availability in patients with normal prothrombin and activated partial thromboplastin times. Isolated PF3 availability defect occurred in patients with ages between 2 and 65 yr and had a female preponderance (M:F=1:2). One fifth of the patients had a positive family history of similar mild bleeding diathesis, indicating an autosomal dominant pattern of inheritance. All patients presented with mild bleeding manifestations, the commonest symptom being appearance of recurrent ecchymotic spots. In females, menorrhagia was the commonest symptom. A pilot study was conducted on 45 patients to evaluate the therapeutic role of oral soya bean (50 g/d). The clinical response was evaluated after 3 months. Soya therapy resulted in disappearance of bleeding problems in 5 patients and reduction in frequency and severity of bleeding in 26 patients. A repeat PF3 availability test after 3 months of therapy showed complete correction in 4 and partial correction in 12 patients. It is evident from McNemer's test that both the clinical and the laboratory parameters (PF3 availability) showed a similar response to soya therapy (p>0.05). Pre-soya therapy mean PF3 availability values differ significantly from those after soya therapy (p<0.01). Thus, soya bean appears to have a therapeutic potential in isolated PF3 availability defect.

More on false thrombocytopenias: EDTA-dependent pseudothrombocytopenia associated with a congenital platelet release defect

We report herein the case of a 54-year-old woman with a moderate bleeding tendency, diagnosed as an EDTA-dependent pseudothrombocytopenia associated with a congenital platelet release defect. The patient, at the age of 12, had a misleading diagnosis of idiopathic thrombocytopenic purpura and all the recurrent bleeding problems she had during her life were referred to that disease. The recent correct diagnosis of a false thrombocytopenia stimulated further laboratory investigation on the cause of the patient's bleeding tendency with the consequent identification of a congenital platelet deficiency of the arachidonic acid pathway. This finding is of relevant importance for the management of the patient in case of elective surgery or hemorrhagic emergency.

Aspirin, prostaglandin E1 and Quin-2 AM-induced platelet dysfunction: restoration of function by noradrenalin

Studies from our laboratory have demonstrated that adrenalin can restore the function of drug-induced refractory platelets to the action of physiological agonists via a novel mechanism (membrane modulation). In various disease states and clinical conditions the circulating levels of noradrenalin (NA) increase several fold more than adrenalin. Therefore, in this study the influence of NA on three well characterized platelet refractory models has been evaluated. Aspirin-exposed platelets were obtained for these studies from blood of donors who had taken one baby aspirin (80 mgs) per day for four consecutive days. Prostaglandin-exposed platelets were obtained by disaggregating ADP-induced aggregates through addition of prostaglandin E1 (1 microM). Finally, low calcium platelets were obtained by buffering cytosolic free calcium with a calcium specific cell permeant fluorophore, Quin-2 AM (60 microM). Drug-exposed platelets did not aggregate irreversibly when stirred with arachidonate (0.45 mM) or NA 5 microM). However, when treated with NA first, drug-treated platelets regained their sensitivity to the action of arachidonate and aggregated irreversibly. The ability of NA to restore the sensitivity of drug-induced refractory platelets was effectively blocked by yohimbine (10 microM), an alpha 2 adrenoceptor antagonist. Results of these studies suggest that NA, similar to the action of adrenalin, can activate membrane modulation and restore the sensitivity of platelets to the action of physiological agonists under a variety of experimental conditions.

Structural defects in inherited and giant platelet disorders

As diverse as the group of inherited structural defects and giant platelet disorders presented in this chapter may seem, there is a common thread that ties them together. All appear to represent some form of membrane aberration. Sometimes only a small inclusion identifies the membrane defect, sometimes a massive increase in size. In others, whole populations of organelles are missing or surface membranes lack specific glycoproteins essential for their function. All of them are born in the deep recesses of a hidden cell, the bone marrow megakaryocyte. Getting the megakaryocyte out into the light of day, or at least into a culture medium, should certainly lead to the solution of many, if not all, of the disorders of platelet membranes and membrane disorders. We have not been completely successful in our efforts to study the megakaryocyte in vitro. As a result, we do not yet understand the normal megakaryocyte, much less normal platelet. The megakaryocyte presents one of the greatest of challenges to our understanding of membrane biology. As our knowledge of how its cytoplasm fills with interiorly and exteriorly derived membranes, and the mechanisms underlying their organization into platelet surfaces, channels of the OCS and DTS, membrane complexes, and five kinds of organelles become clear, our ability to define the basic nature and inheritance of defects will improve rapidly. Within the next decade most aspects of platelet molecular genetics and cell biology will be solved.

Heterogeneous defects of platelet secretion and responses to weak agonists in patients with bleeding disorders

Eleven patients with mild bleeding disorders had as a common abnormality, impaired platelet aggregation and secretion with low concentrations (0.5-1.0 micrograms/ml) of collagen and, in most cases, an absence of second phase aggregation with epinephrine. Platelet granule contents were normal, ruling out storage pool deficiency. To characterize further the platelet abnormalities, we measured aggregation, 14C-5HT secretion, and TxB2 formation induced by a variety of platelet agonists. In eight of the 11 patients we observed decreased initial rates as well as extents of aggregation with one or more weak agonists (ADP, epinephrine, thromboxane A2 and the endoperoxide analogue U44069), i.e. agonists which induced secretion only as a result of aggregation, but normal responses to strong agonists such as arachidonate and high (10 micrograms/ml) concentrations of collagen, which can induce secretion in the presence or absence of aggregation. In all of these patients, TxB2 formation with arachidonate and all concentrations of collagen was normal. The platelet defects in these eight patients have been designated as weak agonist response defects (WARDs). In contrast, the initial aggregation responses to all weak agonists were normal in the three other patients, while secretion and TxB2 formation induced by strong agonists were impaired. Thus, in contrast to the eight patients above, the platelet defects in these three patients were characteristic of defects in the secretion response per se. The results obtained in the 11 patients studied indicate that these types of platelet disorders, previously referred to as primary secretion defects, include defects in the initial platelet responses which precede secretion (WARD) as well as defects in the secretory mechanism per se. Both groups of defects appear to be heterogeneous in nature.

Platelet granule disorders

The present review has cataloged the inherited and acquired disorders of platelet granules. Unfortunately, a mere listing of different conditions in which dense bodies, alpha granules, or both are decreased, absent, or fused does little to define their importance in human platelet physiology or as a causative factor in hemorrhagic disease. The inherited disorders serve as the best index of granule involvement in platelet hemostatic function. Our experience with storage pool deficiency in patients with Hermansky-Pudlak syndrome has suggested that in many individuals virtual absence of dense bodies and their contents does not present a serious threat to hemostasis. Placing HPS patients on aspirin did not cause spontaneous hemorrhage, suggesting that secretion of dense body contents and synthesis of endoperoxides and thromboxane A2 are not absolutely essential for platelet function. However, the literature strongly suggests that many patients with HPS and SPD face a serious risk from bleeding, and hemorrhage may cause death. We can only conclude that some patients with HPS have platelet defects or other hemostatic problems that render SPD a far more serious threat than in other patients who appear to have the same disease. Dense bodies of and by themselves do not appear absolutely required for platelet function. Isolated deficiency of alpha granules presents the same enigma. Only a few patients with this rare inherited disease have been reported. They are generally considered to have mild to severe hemorrhagic problems. However, the past medical history of our two patients with GPS has recently been reviewed and platelet function studies repeated. Despite the mild thrombocytopenia, they are free of any significant bleeding episodes and their platelet function appears virtually normal. Our findings do not support the concept that alpha granules are essential for platelet function. The only condition that seems to support a critical role for storage organelles in hemostasis is the combined alpha-granule, dense body deficiency in one patient reported by Weiss. This patient does have bleeding problems. However, it is difficult to draw conclusions based on a single patient, and the discovery of other patients will help to clarify the hemostatic problem of patients with dual storage organelle deficiencies. In the meantime, we have prepared platelets from normal individuals free of storage granules by sedimentation through gradients containing cytochalasin B. The function of the normal agranular platelets is compromised, but they do respond to some aggregating agents.(ABSTRACT TRUNCATED AT 400 WORDS)

Determination of platelet factor 3 by thrombin generation using a micro-coagulation assay

Platelet factor 3 activity is usually determined by the Stypven method in which factor Xa generation is measured indirectly. The determination is dependent on factors I, II, V, X in the test sample. A coagulation assay for platelet factor 3, which measures the thrombin generation promoted by platelet factor 3, is presented. The test depends on platelet factor 3 only, because factors II, Xa, V, fibrinogen and Ca++ are added in excess. The usability of the new method is shown by platelet factor 3 determinations in patients with various platelet diseases, after ingestion of aspirin and in samples of platelet concentrates before and after storage.

Isolated deficiency of platelet procoagulant activity

This is a study of a 34 year old woman with a moderate to severe bleeding disorder in whom impaired platelet procoagulant activity (PPA) was found by several methods, including tests of factor 3 availability (PF-3a), prothrombin consumption and contact activation. No deficiencies of platelet adhesion, aggregation, secretion, metabolism or granule-bound substances were detectable. Under adequate platelet coverage, this woman underwent two surgical procedures without difficulty. These findings demonstrate the role of PPA in hemostasis and indicate that a defect in PPA can be an isolated occurrence. The abnormalities in PF-3a found in this patient could be due to the diminished number of factor V binding sites, resulting in impaired factor Xa binding, found in separate studies by Majerus et al.

Studies of platelet 5-hydroxytryptamine (serotonin) in storage pool disease and albinism

Platelets in patients with storage pool disease are markedly deficient in a nonmetabolic (storage) pool of ADP that is important in platelet aggregation. They are also deficient in ATP, although to a lesser degree. In seven patients with this disorder, including one with albinism, platelet 5-hydroxytryptamine (5-HT) levels were reduced in proportion to the reduction in ATP (r = 0.94). Their platelets show diminished capacity to absorb [(14)C]5-HT, and the type of defect was similar to that produced in normal platelets by reserpine, a drug known to inhibit the uptake of 5-HT by the platelet dense granules. Storage pool-deficient platelets also converted more [(3)H]5-HT to [(3)H]5-hydroxyindoleacetic acid than did normal platelets, and the platelets in one of two patients studied contained increased amounts of 5-HT metabolites. The above findings, together with those reported previously, support the conclusion that the capacity of the dense granules (which may be either diminished or functionally abnormal) for storing 5-HT is decreased in storage pool disease; as a result, the 5-HT that enters the platelet may be more exposed to monoamine oxidases present on mitochondrial membranes. This diminished storage capacity (for 5-HT) may also explain why preincubating platelet-rich plasma with 5-HT for 45 min without stirring inhibits subsequent platelet aggregation by 5-HT to a greater degree in patients with storage pool disease than in normal subjects. The latter finding is also consistent with the theory that the aggregation of platelets by 5-HT is mediated by the same receptors on the plasma membrane that are involved in its uptake. The diminished release of platelet-bound [(14)C]5-HT by collagen that we found in these patients, as well as findings in previous studies, suggests that the release reaction may also be abnormal in storage pool disease.