Experience With Pre-procedural Hemostatic Medications versus Platelet Transfusion in Patients With Platelet Storage Pool Deficiency.

BackgroundStorage pool deficiency (SPD) is a rare bleeding disorder characterized by reduction in the number of delta granules within platelets, interfering with hemostasis. Current literature lacks well-designed studies from which to draw concrete conclusions regarding pre-procedural management of bleeding complications. Objective: The purpose of this study is to describe bleeding and safety outcomes of SPD patients receiving either pre-procedural platelet transfusions or platelet-sparing regimens. Methods: An exploratory retrospective cohort study was conducted among SPD patients, comparing major bleeding events between those who received platelet transfusion and those who received desmopressin, tranexamic acid, and/or aminocaproic acid within 24 hours prior to procedure. Results: Rates of major bleeding were not found to be higher among patients who received a platelet-sparing regimen [platelet-sparing: 2/25 (8%); platelet transfusion: 2/29 (6.9%); P = .99]. Incidence of non-major bleeding was higher in the platelet transfusion group, but this was not statistically significant [platelet-sparing: 0/25 (0%); platelet transfusion: 3/29 (10.3%); P = .24]. Treatment-related adverse effects were observed following 8 of 54 procedures (14.8%). Conclusion: Use of a platelet-sparing regimen was not associated with a significantly higher incidence of major or non-major bleeding events. Future prospective trials are recommended to compare outcomes between therapies.

Novel GATA1 Variant Causing a Bleeding Phenotype Associated with Combined Platelet α-/δ-Storage Pool Deficiency and Mild Dyserythropoiesis Modified by a SLC4A1 Variant.

Germline defects in the transcription factor GATA1 are known to cause dyserythropoiesis with(out) anemia and variable abnormalities in platelet count and function. However, damaging variants closely located to the C-terminal zinc finger domain of GATA1 are nearly unknown. In this study, a 36-year-old male index patient and his 4-year-old daughter suffered from moderate mucocutaneous bleeding diathesis since birth. Whole exome sequencing detected a novel hemizygous GATA1 missense variant, c.886A>C p.T296P, located between the C-terminal zinc finger and the nuclear localization sequence with non-random X-chromosome inactivation in the heterozygous daughter. Blood smears from both patients demonstrated large platelet fractions and moderate thrombocytopenia in the index. Flow cytometry and electron microscopy analysis supported a combined α-/δ (AN-subtype)-storage pool deficiency as cause for impaired agonist-induced platelet aggregation (light transmission aggregometry) and granule exocytosis (flow cytometry). The absence of BCAM in the index (Lu(a-b-)) and its low expression in the daughter (Lu(a-b+)) confirmed a less obvious effect of defective GATA1 also on erythrocytes. Borderline anemia, elevated HbF levels, and differential transcription of GATA1-regulated genes indicated mild dyserythropoiesis in both patients. Furthermore, a mild SLC4A1 defect associated with a heterozygous SLC4A1 c.2210C>T p.A737V variant maternally transmitted in the daughter may modify the disease to mild spherocytosis and hemolysis.

Platelet Storage Pool Deficiency and Elevated Inflammatory Biomarkers Are Prevalent in Postural Orthostatic Tachycardia Syndrome.

A significant number of postural orthostatic tachycardia syndrome (POTS) patients have platelet delta granule storage pool deficiency (δ-SPD). The etiology of POTS is unknown but a number of laboratories, including ours, have reported elevations of G-protein-coupled adrenergic receptor and muscarinic acetylcholine receptor autoantibodies in POTS patients, detected by a variety of techniques, suggesting that the disorder is an autoimmune condition. Thus, it could also be considered an inflammatory disease. In a pilot study, we investigated a limited number of platelet-related cytokines and chemokines and discovered many that were elevated. This case−control study validates our pilot study results that POTS patients have an activated innate immune system. Plasma of 35 POTS patients and 35 patients with unexplained bleeding symptoms and categorized as "non-POTS" subjects was analyzed by multiplex flow cytometry to quantify 16 different innate immune system cytokines and chemokines. Electron microscopy was used to quantify platelet dense granules. Ten of 16 biomarkers of inflammation were elevated in plasma from POTS patients compared to non-POTS subjects, with most of the differences extremely significant, with p values < 0.0001. Of particular interest were elevations of IL-1ß and IL-18 and decreased or normal levels of type 1 interferons in POTS patients, suggesting that the etiology of POTS might be autoinflammatory. All POTS patients had δ-SPD. With a growing body of evidence that POTS is an autoimmune disease and having elevations of the innate immune system, our results suggest a potential T-cell-mediated autoimmunity in POTS characteristic of a mixed-pattern inflammatory disease similar to rheumatoid arthritis.

Circumcision bleeding rates in patients diagnosed with delta-storage pool deficiency later in life.

BACKGROUND: Male circumcision is a common procedure, generally performed during the newborn period. Bleeding is an uncommon but feared complication of circumcision. Few reports have evaluated circumcision bleeding rates in patients with bleeding disorders. OBJECTIVES: To study circumcision bleeding rates in male subjects who were diagnosed later in life with delta-storage pool deficiency (δ-SPD). METHODS: We retrospectively reviewed the medical records of male subjects (≤18 years of age) who were circumcised without hemostatic prophylaxis prior to δ-SPD diagnosis from 2000 to 2020. Bleeding rates and severity were the main outcomes evaluated. We collected demographic data, bleeding scores using a validated assessment tool, laboratory data, and platelet electron microscopy results. A descriptive analysis was performed. RESULTS: Twenty-five male subjects were included. The median bleeding score at presentation was 3.5 (range: 2-9). The diagnosis was confirmed using platelet electron microscopy. A value of <2 dense granules/platelet was considered abnormal. Circumcision was performed at a median age of 2 days (range: 1 day to 4 months). None of the subjects had intraoperative or postoperative bleeding. With a bleeding rate of zero, we suggest that newborn males with a family history of δ-SPD may be safely circumcised without hemostatic prophylaxis.

An Investigation of ABO Blood Type and the Platelet Delta Granule Storage Pool.

Individuals with bleeding tendencies are more likely to have blood type O than blood types A, B, or AB. Platelet storage pool deficiencies are a lesser-known group of bleeding disorders which often go undiagnosed and may account for a significant number of patients with unexplained bleeding defects. We hypothesized that patients with platelet δ-storage pool deficiency might also have a predominance of type O blood. A retrospective review of medical records of 2,020 patients with unexplained bleeding and evaluated for δ-storage pool deficiency was performed. Correlations between dense granule numbers, blood type, and von Willebrand factor were analyzed for statistical differences. 51.5% of blood samples were blood type O compared to an incidence of 44.0% in the U.S. population. There was a significant association of vWF and blood type O but not with the delta storage pool. There is a preponderance of blood type O in the study population compared to the U.S. population. There is no statistically significant link between blood type O and lower dense granule numbers in this study.

Platelet storage pool disorder: multidisciplinary planning in pregnancy.

A 32-year old primigravida woman presented for antenatal care giving a history that her mother had platelet storage pool disorder (PSPD). The patient was subsequently diagnosed with PSPD during her pregnancy and had a caesarean delivery for breech presentation at 39 weeks. In this paper, we discuss the basic science, inheritance pattern, symptoms and management of this condition, alongside the antenatal and intrapartum and postnatal management specific to it, highlighting the need for a multidisciplinary approach to care. PSPD refers to a group of rare conditions involving defects in platelet granule storage or secretion, which leads to abnormal aggregation and activation of platelets. There are both genetic and acquired forms of the condition. It is a functional platelet disorder, meaning platelet counts will usually remain in the normal range. The diagnosis may be suspected due to characteristic signs and symptoms, but patients may also be asymptomatic. There have been only a few documented cases of pregnant women with PSPD; therefore, management is not clear. Vaginal delivery is not contraindicated, however, postpartum haemorrhage should be anticipated and planned for the use of deamino D-arginine vasopressin (DDAVP), tranexamic acid, prophylactic oxytocics and prompt access to blood products, including platelets, if required. This case highlights the need for effective multidisciplinary teamwork between obstetricians, anaesthetists and haematologists to ensure high-quality care and enable careful intrapartum management planning.

Platelet Electron Microscopy: Utilizing LEAN Methodology to Optimize Laboratory Workflow.

BACKGROUND: Platelet electron microscopy (PEM) is the gold standard methodology for diagnosing storage pool disorder, defined as a paucity of delta granules, alpha granules, or both. PEM literature is limited with few published resources and without well-developed interlaboratory standardization for the preparation and examination of platelet samples. METHODS: Whole mount (WM) dense body (DB) counts for 300 pediatric cases were reviewed to determine whether counting fewer platelets could yield the same results. For 6 cases, DB average was determined on the day of WM preparation and on 2 consecutive days. Both WM and thin section (TS) preparations were examined for all cases. RESULTS: Employing LEAN methodology, an algorithm was developed to markedly decrease the number of platelets counted and still ensure accurate results. WMs decay with time; a statistically significant difference in DB counts was noted between day 0 and day 1 (p < .1). Twelve of 300 cases required both WM and TS preparations for a complete diagnosis. CONCLUSION: It is possible to maintain accuracy and decrease 100 platelet DB counts by >75%. WMs must be counted on the day they are prepared to avoid false paucity of DB secondary to sample decay. An accurate evaluation of platelet morphology requires both the WM and TS techniques.

Flow cytometric mepacrine fluorescence can be used for the exclusion of platelet dense granule deficiency.

BACKGROUND: δ-storage pool disease (δ-SPD) is a bleeding disorder characterized by a reduced number of platelet-dense granules. The diagnosis of δ-SPD depends on the measurement of platelet ADP content, but this test is time consuming and requires a relatively large blood volume. Flow cytometric analysis of platelet mepacrine uptake is a potential alternative, but this approach lacks validation, which precludes its use in a diagnostic setting. OBJECTIVES: To evaluate the performance of platelet mepacrine uptake as a diagnostic test for δ-SPD. PATIENTS/METHODS: Mepacrine fluorescence was determined with flow cytometry before and after platelet activation in 156 patients with a suspected platelet function disorder and compared with platelet ADP content as a reference test. Performance was analyzed with a receiver operating characteristic (ROC) curve. RESULTS: Eleven of 156 patients had δ-SPD based on platelet ADP content. Mepacrine fluorescence was inferior to platelet ADP content in identifying patients with δ-SPD, but both mepacrine uptake (area under the ROC curve [AUC] 0.87) and mepacrine release after platelet activation (AUC 0.80) had good discriminative ability. In our tertiary reference center, mepacrine uptake showed high negative predicitive value (97%) with low positive predictive value (35%). Combined with a negative likelihood ratio of 0.1, these data indicate that mepacrine uptake can be used to exclude δ-SPD in patients with a bleeding tendency. CONCLUSION: Mepacrine fluorescence can be used as a screening tool to exclude δ-SPD in a large number of patients with a suspected platelet function disorder.

Defective Zn2+ homeostasis in mouse and human platelets with α- and δ-storage pool diseases.

Zinc (Zn2+) can modulate platelet and coagulation activation pathways, including fibrin formation. Here, we studied the (patho)physiological consequences of abnormal platelet Zn2+ storage and release. To visualize Zn2+ storage in human and mouse platelets, the Zn2+ specific fluorescent dye FluoZin3 was used. In resting platelets, the dye transiently accumulated into distinct cytosolic puncta, which were lost upon platelet activation. Platelets isolated from Unc13d-/- mice, characterized by combined defects of α/δ granular release, showed a markedly impaired Zn2+ release upon activation. Platelets from Nbeal2-/- mice mimicking Gray platelet syndrome (GPS), characterized by primarily loss of the α-granule content, had strongly reduced Zn2+ levels, which was also confirmed in primary megakaryocytes. In human platelets isolated from patients with GPS, Hermansky-Pudlak Syndrome (HPS) and Storage Pool Disease (SPD) altered Zn2+ homeostasis was detected. In turbidity and flow based assays, platelet-dependent fibrin formation was impaired in both Nbeal2-/- and Unc13d-/- mice, and the impairment could be partially restored by extracellular Zn2+. Altogether, we conclude that the release of ionic Zn2+ store from secretory granules upon platelet activation contributes to the procoagulant role of Zn2+ in platelet-dependent fibrin formation.

Functional Classification of Paediatric Patients with Non-syndromic Delta-Storage Pool Deficiency.

Storage pool disease (SPD) covers a group of platelet defects in which α- and/or delta-granules are reduced or cannot be secreted adequately in response to agonists. The detection of delta-granule release defects is hampered by a lack of fast and feasible tests. We aimed to implement a flow cytometry-based kinetic mepacrine assay to better identify and subgroup childhood patients with a mild to moderate bleeding diathesis and compare our method to established laboratory tests. We analysed 50 children with suspected SPD whose initial parameters were re-assessed in a second site visit. Mepacrine uptake and release patterns were correlated with CD63 exposure, platelet ADP/ATP release and content, and the bleeding score ascertained by the ISTH-BAT. Mepacrine release was overall significantly reduced in investigated patients compared with controls. Summarizing, our time-resolved approach proved to be a quick and inexpensive tool that was additionally able to distinguish between mepacrine uptake, mepacrine release, and combined defects. Classification of patients using such a kinetic assay makes it feasible to sensitively detect frequently missed SPD and to group these patients for further analyses and clinical correlations.

Variation in Platelet Delta Granules Over Time in Young Women Undergoing Evaluation for Heavy Menstrual Bleeding.

Delta-granule platelet storage pool deficiency (δ-PSPD) is a qualitative platelet function defect associated with variable bleeding phenotypes. Platelet electron microscopy (EM) is commonly utilized to evaluate for δ-PSPD, but intrapatient variability in platelet δ-granule numbers by EM is currently unknown. Fifteen young women aged 11 to 17 years presenting to a young women's hematology clinic for the evaluation of heavy menstrual bleeding underwent platelet EM testing at their initial hematology clinic visit and at 1 and 3 months later. Platelet aggregation of platelet-rich plasma by light transmission was also performed on all patients at their initial visit. Eight patients had average δ-granules per platelet consistently ≥2. Three patients were found to have average δ-granules per platelet <2 on initial testing, 2 of which reverted to ≥2 on subsequent testing. When initial average δ-granules per platelet was ≥2, initial repeat testing remained so in 83% (95% confidence interval [CI], 52%-98%) of cases and subsequent repeat testing remained so in 75% (95% CI, 43%-95%) of the cases. Platelet aggregation testing was abnormal in 53% of patients, and there was no apparent correlation between platelet EM findings and platelet aggregation testing. In this small group of young women presenting for the evaluation of bleeding symptoms, we found that almost half of the patients had substantial variability in platelet EM results. Given other identified limitations in platelet EM testing, and the intrapatient variability identified in this study, providers should use caution in utilizing EM in isolation to diagnose δ-PSPD.

Weak correlation of bleeding scores to platelet electron microscopy: A retrospective chart review of pediatric patients with delta-storage pool disorder.

BACKGROUND: Delta granule storage pool deficiency (δ-SPD) is a rare platelet disorder in which a deficiency of platelet granules leads to poor aggregation, resulting in varying clinical bleeding phenotypes. Children with δ-SPD have variable laboratory results, making the proper diagnosis and evaluation controversial. OBJECTIVES: To describe the demographic and laboratory trends of this population and to assess the value of electron microscopy in diagnostic evaluation and its correlation to bleeding symptoms. METHODS: We performed a retrospective review of 109 pediatric patients diagnosed with δ-SPD. We collected demographic information and bleeding scores using a validated bleeding assessment tool. A descriptive and exploratory analysis was performed. RESULTS: The majority of patients were female, with an average age at diagnosis of 11.61 years. Females were diagnosed at a significantly older age presenting most often with menorrhagia, while males presented most commonly with epistaxis. The majority showed normal lumiaggregometry, the mean platelet electron microscopy (PEM) value was 2.37, and the mean bleeding score was 6. Bleeding assessment tool and PEM had a significantly weak correlation. CONCLUSIONS: Patients with more dense granules per platelet had higher bleeding scores than those with fewer dense granules per platelet. The current body of evidence does not favor the use of PEM in routine clinical practice, and results are difficult to interpret. In patients with severe mucocutaneous bleeding symptoms and normal platelet aggregation studies, consideration should be given to an alternative diagnosis and further evaluation is warranted.

Angiomatoid Fibrous Histiocytoma With Paraneoplastic Platelet Storage Pool Deficiency.

Angiomatoid fibrous histiocytoma is a rare soft tissue tumor usually discovered in young individuals. This tumor is often mistaken for a hematoma and typically misdiagnosed. It is commonly found in the extremities and may be associated with a site of recent or previous trauma. Characteristic histology includes nodules of histiocytoid spindle cells with pseudoangiomatoid spaces, fibrous pseudocapsules, and lymphoid cuffing. We describe the case of an 8-year-old girl who presented after incision and drainage of a superficial thigh lesion and experienced subsequent chronic bleeding of her wound. Her initial presentation was concerning for an underlying bleeding disorder, and laboratory analysis uncovered a paraneoplastic platelet function disorder that resolved with therapy of the primary tumor.

Combined alpha-delta platelet storage pool deficiency is associated with mutations in GFI1B.

Combined alpha-delta platelet storage pool deficiency is characterized by the absence or reduction in the number of both alpha granules and dense bodies. This disorder can have variable severity as well as a variable inheritance pattern. We describe two patients from unrelated families with combined alpha-delta storage pool deficiency due to mutations in GFI1B, a zinc finger protein known to act as a transcriptional repressor of various genes. We demonstrate that this disease is associated with either a heterozygous mutation (de novo or familial) abrogating the binding of the zinc fingers with the promoter of its target genes, or by hypomorphic biallelic mutations in GFI1B leading to autosomal recessive inheritance.

Storage pool diseases illuminate platelet dense granule biogenesis.

Platelet dense granules (DGs) are membrane bound compartments that store polyphosphate and small molecules such as ADP, ATP, Ca2+, and serotonin. The release of DG contents plays a central role in platelet aggregation to form a hemostatic plug. Accordingly, congenital deficiencies in the biogenesis of platelet DGs underlie human genetic disorders that cause storage pool disease and manifest with prolonged bleeding. DGs belong to a family of lysosome-related organelles, which also includes melanosomes, the compartments where the melanin pigments are synthesized. These organelles share several characteristics including an acidic lumen and, at least in part, the molecular machinery involved in their biogenesis. As a result, many genes affect both DG and melanosome biogenesis and the corresponding patients present not only with bleeding but also with oculocutaneous albinism. The identification and characterization of such genes has been instrumental in dissecting the pathways responsible for organelle biogenesis. Because the study of melanosome biogenesis has advanced more rapidly, this knowledge has been extrapolated to explain how DGs are produced. However, some progress has recently been made in studying platelet DG biogenesis directly in megakaryocytes and megakaryocytoid cells. DGs originate from an endosomal intermediate compartment, the multivesicular body. Maturation and differentiation into a DG begins when newly synthesized DG-specific proteins are delivered from early/recycling endosomal compartments. The machinery that orchestrates this vesicular trafficking is composed of a combination of both ubiquitous and cell type-specific proteins. Here, we review the current knowledge on DG biogenesis. In particular, we focus on the individual human and murine genes encoding the molecular machinery involved in this process and how their deficiencies result in disease.

Clinical and Laboratory Findings in Patients with δ-Storage Pool Disease: A Case Series.

Platelet δ-storage pool disease (δ-SPD) is a platelet function disorder characterized by a reduction in the number or content of dense granules. Reports on δ-SPD are mostly limited to case presentations. We aimed to retrospectively describe a series of patients with δ-SPD to better characterize the disease. We studied 16 patients with congenital or acquired δ-SPD. Lumiaggregometry, α- and δ-granules content, platelet ultrastructure, αIIbß3 integrin, and glycoprotein Ib (GPIb) activation were assessed. Most of the patients generally demonstrate mild to moderate bleeding diathesis. Platelet aggregation studies showed moderate abnormalities with variable profiles, while all the individuals had almost complete absence of adenosine triphosphate release. Mepacrine capture, CD63 expression, and study of dense granules by electron microscopy enabled to distinguish different subtypes of δ-SPD with quantitative or qualitative defect. Surprisingly, significantly decreased GPIb expression levels after platelet activation with thrombin receptor activating peptide 50 µM were found, suggesting that GPIb-impaired mobilization may represent an additional feature of the disorder. In conclusion, δ-SPD represents a complex disorder with various clinical and biological aspects, requiring a great deal of expertise to be properly diagnosed.

Platelet granules - secretory and secretive.

The article reviews three recent publications addressing physiological and pathological aspects of platelet granules and release as well as limitations of recent screening tests for diagnosis of non-syndromic inherited δ-storage pool disease (1-3).