Platelet function in the myelodysplastic syndromes

Bleeding in myelodysplastic syndromes (MDS) is often related to thrombocytopenia. However, because MDS is a stem cell disorder, it is conceivable that platelet function (PF) abnormalities may play a role as well. A few studies have been reported, mainly with platelet aggregation (PA). A summary of the information discloses that about 68 MDS patients have been studied. Despite some conflicting data, it can be concluded that PA defects are quite common in MDS. About 75% of MDS patients demonstrated reduced PA with epinephrine, followed by decreased PA with arachidonic acid (54%), ADP (46%), collagen (43%), and ristocetin (22%). Several other PFs were studied, but the data require caution in interpretation. Despite the relatively high incidence of platelet dysfunction, bleeding in MDS patients is uncommon, with episodes tending to be mild, although recurrent. Nevertheless, some correlation between PA abnormalities and the tendency to bleed has been suggested. As patients demonstrate more PA defects, they tend to bleed more. Some authors suggest that PF studies may assist in diagnosing tough cases of MDS, as well as serving as prognostic markers. A large-scale study testing PF in a large number of MDS patients is required and is expected.     

Danazol for the treatment of thrombocytopenia in patients with myelodysplastic syndrome

Thrombocytopenia is a poor prognostic indicator in the myelodysplastic syndromes (MDS). Treatment options for patients with symptomatic thrombocytopenia are limited. Danazol, an attenuated androgen, may have some efficacy in increasing the platelet count of patients with MDS. We retrospectively reviewed 33 patients with primary MDS who were treated with danazol for 6 or more weeks. After 6 weeks on danazol, the mean platelet count increased from 42 x 10(9)/L to 60 x 10(9)/L (P < 0.015), and 25 out of 33 patients (76%) had an increase in their platelet counts. Following 12 weeks of treatment, the mean platelet count increased to 67 x 10(9)/L (P < 0.005), and 21 out of 29 patients (72%) had an increase in their platelet counts. Seven out of nine patients no longer required platelet transfusions because bleeding stopped after 6 weeks on danazol. Mean duration of response was 10 months (range 2-68 months). Responses were seen in all French-American-British (FAB) subtypes and in all International Prognostic Scoring System (IPSS) scores. Therapy was well tolerated. Danazol may be effective in MDS patients who are thrombocytopenic.     

Clinical features of atypical refractory anemia (RA)

Twenty-three patients with bicytopenia or pancytopenia were retrospectively studied. The patients with underlying disorders, blast count of more than 5% on bone marrow (BM) aspirate, blast count of more than 1% on peripheral blood or ringed sideroblast count of more than 15% on BM aspirate were excluded. According to Yoshida's criteria, 23 patients were classified into 6 subtypes [AA (aplastic anemia)1: typical AA, AA2: atypical AA, MDS (myelodysplastic syndrome)3: typical RA (refractory anemia, MDS4-6: atypical RA], and AA1 7 cases; AA2 2 cases; MDS3 5 cases; MDS4 1 case; MDS5 2 cases; MDS6 6 cases. To clarify the clinical features of atypical RA group (MDS4-6), we investigated ferrokinetics, RBC life span, karyotype, serum Epo (erythropoietin) concentration, response to therapy and prognosis. Results were as follows: 1) all three RA patients who were younger than 30 years old were included in atypical RA group, 2) in ferrokinetics study PID (plasma iron disappearance time) values of MDS4 and MDS6 patients ranged between those of AA1 and those of MDS3 patients (5 of 7 patients), 3) two cases who developed leukemia belonged to typical RA group, 4) patients with atypical RA showed response to therapy and their prognosis were better than those with typical RA. These observations suggest that atypical RA have different clinical features from typical RA.     

A probable double heterozygous type II von Willebrand's disease with increased ristocetin induced platelet aggregation.

We have identified a patient with von Willebrand's disease (vWD) resembling type IIB vWD, with increased ristocetin induced platelet aggregation (RIPA), the absence of the large multimers of von Willebrand factor (vWF) in plasma, and the presence of the large multimers in platelets in whom a family study indicated a probable double heterozygous inheritance pattern. The propositus was a 12-year-old boy with frequent epistaxis and bruising. Abnormal hemostatic findings included a prolonged bleeding time (BT), decreased levels of factor VIII coagulant activity (VIIIC), von Willebrand factor antigen (vWF:Ag), ristocetin cofactor (RCof), and an increased RIPA. In the presence of ristocetin, binding of the patient's plasma vWF to normal platelets was increased but binding of normal vWF to his platelets was normal. SDS-agarose gel (1.5%) electrophoresis revealed that plasma vWF lacked the large multimers, and 3.0% gel electrophoresis revealed that the multimers had a 5-band pattern similar to normal. The above findings were consistent with type IIB vWD, but 1-deamino[8-D-arginine]-vasopressin (DDAVP) infusion resulted in a shortened BT and the transient appearance of large multimers without a decrease in the platelet count. Family studies revealed that his mother has mild bleeding symptoms, decreased VIIIC, vWF:Ag, and RCof levels and normal to slightly reduced RIPA with a multimer pattern consistent with type I vWD. In contrast, the father, sister, and paternal grandfather were asymptomatic, with a slightly decreased VIIIC level but a normal BT and vWF:Ag and RCof levels. Their RIPA and vWF binding to normal platelets were increased, but unlike the propositus their plasma contained large multimers. We concluded that the propositus is a type IIB-like variant differing from previously reported IIB variants in two ways: 1) his response to DDAVP and 2) a possible double heterozygous mode of inheritance rather than the usual dominant route.     

Inherited bleeding disorders in Indian women with menorrhagia

In order to define the prevalence of haemostatic defects in women presenting with menorrhagia in our region, the coagulation data on women bleeders investigated in the Department of Haematology, AIIMS, were analysed. A total of 337 of the 2200 menorrhagic women investigated were characterized to have an inherited bleeding disorder; 221 of these 337 women presented with menorrhagia alone while 116 also had other associated bleeding manifestations as prolonged bleeding from injury site, ecchymotic patches in the skin, epistaxis, haematomas, haemarthroses and major bleeds like intracerebral bleeding. The tests performed included bleeding time (BT), platelet count, prothrombin time (PT), prothrombin consumption index (PCI), activated partial thromboplastin time (APTT), PF3 release with adenosine diphosphate (ADP) at 0 and 20 min, total PF3 assay and platelet Aggregation studies with collagen, ADP, adrenaline, arachidonic acid and ristocetin. Coagulation factor assays, von Willebrand antigen estimation, ristocetin cofactor assay and electron microscopy were performed wherever necessary. Inherited platelet dysfunction was seen in 283 (83.9%) of the patients. Amongst these, isolated PF3 availability defect was seen in 163 (48.4%) cases. Glanzman's thrombasthenia was seen in 30 (8.9%) patients, Storage pool disease in eight (2.4%) patients, arachidonic acid pathway defect in five (1.5%) patients and Bernard-Soulier Syndrome in six (1.8%) patients. In 71 (21.1%) patients, the platelet function defect could not be classified into any specific subtypes. Inherited defects of coagulation were observed in 54 (16%) of the cases. Amongst these, von Willebrand disease (vWD) was the most frequent being seen in 40 (11.9%) of the cases. Factor XIII deficiency was seen in one (0.3%), factor X deficiency in four (1.2%), factor VII deficiency in one (0.3%) and factor XII deficiency in one (0.3%) of the patients. It is concluded that although hereditary platelet function defects constitute a large majority of women bleeders in India but among the coagulation defects, vWD is the commonest as reported from the caucasian population. It is thus suggested that in women presenting with menorrhagia, screening tests for haemostasis especially for vWD and inherited platelet function defects must be performed.     

Myelodysplastic syndrome accompanied by Evans syndrome

Various cases of myelodysplastic syndrome (MDS) with diverse immunological disorders have been reported by many investigators. In this case report, we present a 70-year-old woman who had been diagnosed as having MDS and liver cirrhosis (LC) type C for 20 months, and who finally developed autoimmune phenomena against autologous blood cells. She was admitted to our hospital in order to evaluate her advanced anemia, thrombocytopenia and fatigue. The laboratory data at admission were as follows: hemoglobin 5.3 g/dl, red blood cell count 109 x 10(4)/microliter, white blood cell count 1,760/microliter, platelet count 4.3 x 10(4)/microliter and reticulocyte count 1.3%. The direct Coombs test was positive. In addition, anti-platelet antibody was positive, using the MPHA method. With these results, Evans syndrome secondary to MDS or LC was diagnosed. The mechanisms for the development of immunological disorders in patients with MDS or LC have not been fully elucidated. To our knowledge, this patient is one of the rare cases with MDS and Evans syndrome reported in the literature. During the generation process of autoantibodies, the role of HCV antigen in the pathogenesis of Evans syndrome was of interest in this patient.     

Platelet function tests using platelet aggregometry: need for repetition of the test for diagnosis of defective platelet function

Four hundred and ninety seven patients were referred to our center for platelet aggregation studies because of spontaneous mucocutaneous bleeds. All these patients had normal complete blood count, platelet count and peripheral smears except in ten patients of Bernard Soulier Syndrome where platelet count was marginally reduced in the presence of giant platelets. Two hundred and eighty patients were found to have normal platelet aggregation to ADP, collagen, ristocetin and arachidonic acid. Out of the remaining 217 patients, 62 patients were diagnosed to have Glanzmanns thrombasthenia, 10 Bernard Soulier Syndrome, 6 storage pool deficiencies, 7 cyclooxygenase deficiencies and 72 von Willebrand disease. In all the patients with GT and BSS, diagnosis was confirmed with flow cytometry using multiple monoclonal antibodies to GPIIb-IIIa and GPIb-IX. There were sixty patients where initial platelet aggregation studies showed reduced (<30%) aggregation to either ADP, collagen, ristocetin or arachidonic acid in its various combination, however in 12 such patients (20%) the platelet aggregation studies were normal on repetition. All our platelet aggregation studies were done only after assuring that the patient is not taking any medicine for at least 7 – 10 days which may affect the platelet function tests. The present study shows that single atypically abnormal platelet aggregation studies should always be repeated. Finally in 48/217 patients (22%) some aggregation abnormality to one or more of the agonists persisted, although we could not categorize these patients into any clear-cut platelet disorder. None of these 48 patients platelet associated immunoglobulin was increased by flow cytometry. It is possible that large number of patients from that disorder will finally prove to be some form of platelet secretory defect. In north India similar group of defect in a large number of patients have been reported as isolated PF3 abnormality or thrombasthenic thrombopathy.     

Platelet function tests using platelet aggregometry: need for repetition of the test for diagnosis of defective platelet function

Four hundred and ninety seven patients were referred to our center for platelet aggregation studies because of spontaneous mucocutaneous bleeds. All these patients had normal complete blood count, platelet count and peripheral smears except in ten patients of Bernard Soulier Syndrome where platelet count was marginally reduced in the presence of giant platelets. Two hundred and eighty patients were found to have normal platelet aggregation to ADP, collagen, ristocetin and arachidonic acid. Out of the remaining 217 patients, 62 patients were diagnosed to have Glanzmanns thrombasthenia, 10 Bernard Soulier Syndrome, 6 storage pool deficiencies, 7 cyclooxygenase deficiencies and 72 von Willebrand disease. In all the patients with GT and BSS, diagnosis was confirmed with flow cytometry using multiple monoclonal antibodies to GPIIb-IIIa and GPIb-IX. There were sixty patients where initial platelet aggregation studies showed reduced (<30%) aggregation to either ADP, collagen, ristocetin or arachidonic acid in its various combination, however in 12 such patients (20%) the platelet aggregation studies were normal on repetition. All our platelet aggregation studies were done only after assuring that the patient is not taking any medicine for at least 7-10 days which may affect the platelet function tests. The present study shows that single atypically abnormal platelet aggregation studies should always be repeated. Finally in 48/217 patients (22%) some aggregation abnormality to one or more of the agonists persisted, although we could not categorize these patients into any clear-cut platelet disorder. None of these 48 patients platelet associated immunoglobulin was increased by flow cytometry. It is possible that large number of patients from that disorder will finally prove to be some form of platelet secretory defect. In north India similar group of defect in a large number of patients have been reported as isolated PF3 abnormality or thrombasthenic thrombopathy.     

Plasma thrombopoietin (TPO) levels and expression of TPO receptor on platelets in patients with myelodysplastic syndromes

Data on endogenous thrombopoietin (TPO) levels and their regulation in myelodysplastic syndromes (MDS) are sparse. We examined the plasma TPO level of 85 MDS patients by a sensitive enzyme immunoassay and the platelet expression of TPO receptor (TPO-R) protein, which metabolizes endogenous TPO, in 19 MDS patients with an equilibrium binding assay using ¹²⁵I-TPO. The MDS patients had higher plasma TPO levels (7.0 ± 9.3 fmol/ml) than 52 normal subjects ( P < 0.0001). Refractory anaemia (RA) patients ( n  = 39) had higher plasma TPO levels than patients ( n  = 28) with RA with excess blasts (RAEB) or RAEB in transformation (RAEB-t) ( P  = 0.0002), irrespective of similar platelet counts in these groups. The plasma TPO level correlated inversely with the platelet count in RA patients ( P  = 0.0027) but not in RAEB and RAEB-t patients ( P  = 0.7865). These data suggest that the physiological pathway for TPO production and metabolism is conserved, at least partially, in RA, but deranged in RAEB/RAEB-t. The number of TPO-R per platelet was significantly smaller in 19 MDS patients (17.5 ± 13.3) than in normals ( P  = 0.0014), but similar between RA patients and patients with RAEB and RAEB-t. Further, the bone marrow megakaryocyte count, determined in 31 MDS patients, was quite similar between RA patients and patients with RAEB or RAEB-t. Thus, in addition to thrombocytopenia, a reduced platelet TPO-R number may contribute to elevated plasma TPO levels in MDS, and a regulatory pathway for circulating TPO other than platelet TPO-R and marrow megakaryocytes, such as blasts expressing TPO-R, may operate in RAEB/RAEB-t.     

Hemostatic effect of normal platelet transfusion in severe von Willebrand disease patients

Platelet von Willebrand factor (vWF) has been suggested to play an important role in the hemostatic process. Clinical and experimental data indicate that bleeding time (BT) and platelet-vessel wall interaction cannot be normalized unless the defect of platelet vWF is also corrected. We have examined the effect of normal platelet concentrate transfusion 1 hour after cryoprecipitate infusion in five type III von Willebrand disease (vWD) patients. The cryoprecipitate infusion attained normal circulating levels of ristocetin cofactor, vWF antigen, and factor VIII activity. In two patients, cryoprecipitate infusion did not modify the BT (greater than 30 minutes), whereas in the remaining three patients BT was only partially corrected (from greater than 30 to 12, 18, and 21 minutes). However, the immediate platelet transfusion completely corrected the BT in four cases, and in one case it shortened the BT to 8.30 minutes (n = 3 to 8 minutes). In the perfusion study, cryoprecipitate infusion only resulted in a slight increase in platelet deposition (surface coverage range: 2.4% to 11.3%), whereas the platelet concentrate transfusion elicited a more marked improvement (range: 8.2% to 26.4%; P less than .02 v post-cryoprecipitate). These results suggest an important in vivo role of the platelet vWF in supporting platelet-vessel wall interaction. They also give support to the occasional addition of normal platelet transfusion to the cryoprecipitate infusion for the control of serious bleeding episodes resistant to cryoprecipitate in severe vWD patients.     

Familial and constitutional bleeding disorder due to platelet cyclo-oxygenase deficiency

Three family members from two successive generations had a bleeding tendency. Their template bleeding time was prolonged and platelet aggregation induced by ADP and adrenaline showed no second wave; collagen at low to moderate concentrations failed to aggregate and release ATP, whereas higher amounts aggregated and released. Aggregation and release due to thrombin, ristocetin, and synthetic epoxy derivatives (U 44069 and U 46619) were normal. Arachidonate (AA) was inactive, and was not converted either in thromboxane (TX) A2 activity evaluated on the rabbit aorta strip, nor in TXB2 evaluated by radioimmunoassay and by radiochromatography. The parallel impairment of TXB2 and PGE2 formation by the patient's platelets are compatible with a platelet cyclo-oxygenase deficiency. This study suggests that transmission is autosomal dominant, and confirms that cyclo-oxygenase is not needed for aggregation and ATP release by high amounts of collagen.     

Treatment of myelodysplastic syndrome with low-dose human granulocyte colony-stimulating factor: a multicenter study

The objective of this study was to determine the hematopoietic effects and toxicity of low-dose granulocyte colony-stimulating factor (G-CSF) in myelodysplastic syndrome (MDS) patients with neutropenia. Recombinant human G-CSF (Lenograstim) was administered by daily subcutaneous injection with an initial dosage of 0.5 microg/kg per day for 2 weeks. Patients not responding to the initial dosage received the escalated dosage, 1 to 2 microg/kg per day for 2 weeks. Eligibility criteria were the following: French-American-British disease classification subtype refractory anemia (RA), refractory anemia with ringed sideroblasts (RARS), or refractory anemia with excess blasts (RAEB) with an absolute neutrophil count (ANC) of <1.5 x 10(9)/L. Criteria indicating response to treatment were ANC of >1.5 x 10(9)/L and doubling of ANC on at least 2 occasions. Thirty-two MDS patients were recruited from 6 university hospitals. Eighteen patients had RA, 4 had RARS, and 10 had RAEB. Median age was 56.4 years (range, 28-87 years). Twenty-six patients (81.2%) had an increase in ANC from a median of 0.94+/-0.35 x 10(9)/L to 4.24+/-3.78 x 10(9)/L.Three of 6 patients who did not respond to the initial dosage responded to the escalated dosage of 1 microg/kg per day. Eighteen (81.8%) of 22 patients with RA or RARS responded compared with 8 (80%) of 10 patients with RAEB. The response rates in patients with ANCs of <0.5 x 10(9)/L. 0.5 to <1.0 x 10(9)/L, and 1.0 to 1.5 x 10(9)/L were 80%, 70%, and 88.2%, respectively. The side effects were minimal. No significant changes in hemoglobin levels or platelet counts were observed. In conclusion, low-dose G-CSF administered by subcutaneous injection is well tolerated and effective in improving neutropenia in MDS patients.     

Unrelated cord blood transplantation for adult patients with advanced myelodysplastic syndrome

We report the results of unrelated cord blood transplantation (CBT) for 13 adult patients with advanced myelodysplastic syndrome (MDS). The median age was 40 years, the median weight was 51 kg, and the median number of infused nucleated cells was 2.43 x 107/kg. Twelve patients had myeloid reconstitution, and the median time to more than 0.5 x 109/L (5 x 108/L) absolute neutrophil count was 22.5 days. A self-sustained platelet count more than 50 x 109/L was achieved in 11 patients at a median time of 49 days. Acute graft versus host disease (GVHD) occurred in 9 of 12 evaluable patients and chronic GVHD in 8 of 11 evaluable patients. Ten patients are alive and free of disease at between 171 and 1558 days after transplantation. The probability of disease-free survival at 2 years was 76.2%. These results suggest that adult advanced MDS patients without suitable related or unrelated bone marrow donors should be considered as candidates for CBT.     

A retrospective 11-year analysis of obstetric patients with idiopathic thrombocytopenic purpura

Numerous studies have examined the outcomes of infants born to mothers with idiopathic thrombocytopenic purpura (ITP). Fewer studies have discussed the morbidity of obstetric patients with ITP. We describe a retrospective study of 92 women with ITP during 119 pregnancies over an 11-year period. Most women had thrombocytopenia during pregnancy. At delivery, women in 98 pregnancies (89%) had platelet counts lower than 150 x 109/L; most had mild to moderate thrombocytopenia. For many, the pregnancy was uneventful; however, women had moderate to severe bleeding in 25 pregnancies (21.5%). Women in 37 pregnancies (31.1%) required treatment to increase platelet counts. During delivery, 44 women (37.3%) received epidural analgesia without complications, with most having a platelet count between 50 and 149 x 109/L. Most deliveries (82.4%) were vaginal. Bleeding was uncommon at delivery. Infant platelet counts at birth ranged from 12 to 436 x 109/L; 25.2% of infants had platelet counts lower than 150 x 109/L, and 9% had platelet counts lower than 50 x 109/L. Eighteen infants (14.6%) required treatment for hemostatic impairment. Two fetal deaths occurred. One was caused by hemorrhage. ITP in pregnancy carries a low risk, but mothers and infants may require therapy to raise their platelet counts.     

Type 2B von Willebrand's disease due to Val1316Met mutation. Heterogeneity in the same sibship

An analysis was conducted in four members of the same family, two of whom had a history of severe bleeding associated with type 2B von Willebrand's disease (VWD) which, although found to be due to the same mutation, nevertheless exhibited different phenotype patterns in the two subjects involved. Von Willebrand's factor (VWF) multimers were assayed with high- and low-resolution sodium dodecyl sulfate (SDS) agarose gels. The patients were studied before and after intravenous administration of desmopressin (DDAVP) at doses of 0.4 microg/kg body weight. Automatic sequencing techniques were used to analyze VWF gene exon 28. The propositus presented with mild basal thrombocytopenia with ristocetin-induced platelet aggregation (RIPA) at low concentrations of ristocetin. He had a very prolonged bleeding time (BT), and his plasma VWF was found to be lacking in large and intermediate multimers. Thrombocytopenia was observed to intensify transiently after the administration of DDAVP. The propositus' mother, in contrast, presented reduced RIPA while in a basal state, with only partial loss of the high molecular weight VWF multimers. Although she had a very prolonged BT, her platelet count was borderline. Transient correction of BT and a decrease in the platelet count were observed after administration of DDAVP and RIPA was observed at low concentrations of ristocetin. Exon 28 sequencing revealed a G4196A-->Val1316Met mutation in both patients. No other abnormality was detected within this exon. Val1316Met has been reported in type 2B VWD. In conclusion, in the family presented here, the phenotype pattern in one patient was typical of type 2B VWD, whereas the pattern in his mother was closer to type 2A VWD. After administration of DDAVP, however, a type 2B phenotype could be clearly attributed to both, indicating that this drug can be a useful tool for elucidating ambiguous phenotypes.     

Effect of subcutaneous administration of interleukin-1 beta on blood platelet count and serum GM-CSF in patients with myelodysplastic syndrome and aplastic anemia]

Subcutaneous administration of recombinant human Interleukin-1 beta (IL-1 beta) in a dose of 1-3 x 10(4) U/day for 14 to 72 days resulted in an increase in circulating granulocytes and bone marrow monocytes in all the 4 patients examined. Circulating platelet count was also increased in two of four patients with myelodysplastic syndrome (MDS) and aplastic anemia (AA). Bone marrow examination revealed an increase in megakaryocyte count in these patients, whereas the percentage of blast was not changed. An increase in blood platelet count was accompanied by an increase in serum GM-CSF in a patient with AA, whereas serum IL-6 level was not changed throughout the treatment with IL-1 beta. These findings suggest that IL-1 beta may be useful for the treatment of a proportion of patients with MDS and AA who are associated with thrombocytopenia.     

Diagnostic value of serum type IV collagen test in comparison with platelet count for predicting the fibrotic stage in patients with chronic hepatitis C

BACKGROUND: AND AIM: The serum type IV collagen test is now used as a diagnostic aid for the detection of liver fibrosis and cirrhosis. Recently, a platelet count has been reported to be a useful marker for assessing the fibrotic stage in chronic hepatitis C. The aim of this study was to compare the usefulness of the serum type IV collagen test and platelet count for diagnosing the fibrotic stage in chronic hepatitis C patients. METHODS: The diagnostic values were assessed by the use of receiver operating characteristic (ROC) analysis in 165 patients with chronic hepatitis C, with the exception of those patients with cirrhosis. RESULTS: The serum type IV collagen level increased, and the platelet count decreased significantly with the progression of fibrosis staging. As judged from ROC curves, the serum type IV collagen test was more useful than the platelet count for differentiating moderate or severe fibrosis from no or mild fibrosis. At a cut-off value of 110 ng/mL, the serum type IV collagen test had an overall diagnostic accuracy of 75%, while at a cut-off value of 16 x 10(4)/mm(3), the platelet count had a diagnostic accuracy of 70%. The serum type IV collagen test and platelet count were similar in differentiating severe fibrosis from no, mild or moderate fibrosis. Both serum type IV collagen (at a cut-off value of 130 ng/mL) and platelet count (at a cut-off value of 14 x 10(4)/mm(3)) had a diagnostic accuracy of 73%. CONCLUSION: The serum type IV collagen test was slightly superior to the platelet count for assessing the fibrotic stage in patients with chronic hepatitis C.     

Platelet aggregation in whole blood from patients with Glanzmann's thrombasthenia

We examined platelet aggregation in platelet-rich plasma (PRP) and in whole blood from two patients with Glanzmann's thrombasthenia. In PRP, aggregation was measured by monitoring the changes in light absorbance that occurred in response to aggregating agents; to measure platelet aggregation in whole blood, we used a platelet counting technique. In PRP, the patients' platelets showed defective aggregation in response to ADP, adrenaline, arachidonic acid (AA), and collagen, but normal agglutination occurred in response to ristocetin. In whole blood, however, platelet aggregation in response to the aggregating agents appeared to be either very similar to that which occurred in blood from normal subjects or only slightly reduced. There was a reduced response to all concentrations of ADP and to low concentrations of collagen but a normal response to all concentrations of adrenaline, AA, and higher concentrations of collagen. Conversely, there seemed to be an increased agglutination response to ristocetin. The abnormality in our two patients with Glanzmann's thrombasthenia probably lies in the inability of their platelets to form large, macroscopic aggregates rather than in platelet aggregation per se.     

Exaggeration of defective platelet function by methyldopa in hypothyroidism

Platelet function was analyzed in two hypothyroid patients who were taking methyldopa. Results from these two patients are compared to those obtained in seven others with hypothyroidism on no medications. Bleeding times in the two drug patients were 33 and 26 minutes compared to normal values (4.0 to 8.0 minutes) in the other hypothyroid individuals. In addition, platelet aggregation responses to epinephrine, collagen, and ristocetin were abnormal in these two patients; these were normal in the others with hypothyroidism. Repeat studies were done in the first drug patient when she was euthyroid and still receiving methyldopa. Her bleeding time decreased to 11 minutes, platelet retention increased from 31% to 75%, and abnormal aggregation responses corrected to normal. Factor VIII coagulant activity, VIII antigenic activity, VIII ristocetin cofactor activity, and two-dimensional immunoelectrophoresis of VIII antigen were normal. These findings suggest that methyldopa can potentiate the mild platelet function defect seen in patients with hypothyroidism.     

Cytokine-mobilized allogeneic peripheral blood stem cell transplants in children result in rapid engraftment and a high incidence of chronic GVHD

Between October 1995 and October 1998, 24 children aged 9 months to 17 years (median 11 years) underwent cytokine-mobilized allogeneic peripheral blood stem cell (PBSC) transplantation for treatment of hematological disorders. All of the transplants were the first allogeneic transplant for the recipient. Twenty patients were transplanted for hematological malignancies (ALL = 8, AML = 6, CML = 4, MDS = 2) and four patients were transplanted for non-malignant disease (thalassemia major = 2, Wiskott-Aldrich syndrome = 1, Kostmann's syndrome = 1). Nineteen donors were HLA-identical siblings, four were HLA-matched or single antigen mismatched parents, and one was a syngeneic transplant. Donors aged 8 to 38 years (median 15 years, 14 donors <18 years) received G-CSF 10 microg/kg/day subcutaneously beginning 4 days before PBSC collection and were submitted to one to three leukapheresis collections. The median CD34+ cell yield was 7.8 x 106 cells/kg recipient body weight. All patients achieved an ANC >0.5 x 109/l after a median of 13 days (range 10-21). Twenty-three patients eventually achieved platelet transfusion independence. One patient died on day 63 without ever achieving platelet transfusion independence. Four patients received platelet transfusions to maintain a platelet count well above 20 x 109/l due to bleeding complications. Of the 19 evaluable patients, the median time to a non-transfused platelet count of 20 x 109/l was 12 days (range 0-44). Ten of 23 at-risk patients developed acute GVHD grades II to IV, with grades III to IV in four patients. Twelve of 19 patients followed for at least 100 days have developed chronic GVHD (extensive = 2, limited = 10) with an actuarial risk of chronic GVHD of 75% at 1 year. The Kaplan-Meier estimate of event-free survival is 65% at 2 years. Four patients died (GVHD = 3, VOD = 1), three patients relapsed, and one patient with thalassemia major had a late graft failure with autologous recovery. Based upon our experience, allogeneic PBSCT is safe for both pediatric donors and recipients and engraftment of neutrophils and platelets is rapid. Bone Marrow Transplantation (2000) 25, 13-18.