Hermansky-Pudlak Syndrome Research Articles

Hermansky-Pudlak syndrome type 1 causes impaired anti-microbial immunity and inflammation due to dysregulated immunometabolism

Hermansky-Pudlak syndrome (HPS) types 1 and 4 are caused by defective vesicle trafficking. The mechanism for Crohn's disease-like inflammation, lung fibrosis, and macrophage lipid accumulation in these patients remains enigmatic. The aim of this study is to understand the cellular basis of inflammation in HPS-1. We performed mass cytometry, proteomic and transcriptomic analyses to investigate peripheral blood cells and serum of HPS-1 patients. Using spatial transcriptomics, granuloma-associated signatures in the tissue of an HPS-1 patient with granulomatous colitis were dissected. In vitro studies were conducted to investigate anti-microbial responses of HPS-1 patient macrophages and cell lines. Monocytes of HPS-1 patients exhibit an inflammatory phenotype associated with dysregulated TNF, IL-1α, OSM in serum, and monocyte-derived macrophages. Inflammatory macrophages accumulate in the intestine and granuloma-associated macrophages in HPS-1 show transcriptional signatures suggestive of a lipid storage and metabolic defect. We show that HPS1 deficiency leads to an altered metabolic program and Rab32-dependent amplified mTOR signaling, facilitated by the accumulation of mTOR on lysosomes. This pathogenic mechanism translates into aberrant bacterial clearance, which can be rescued with mTORC1 inhibition. Rab32-mediated mTOR signaling acts as an immuno-metabolic checkpoint, adding to the evidence that defective bioenergetics can drive hampered anti-microbial activity and contribute to inflammation.

Knockout of Hermansky-Pudlak Syndrome 4 (hps4) leads to silver-white tilapia lacking melanosomes

Body color is a major factor determining the economic value of farmed tilapia. In the present study, we engineered a silver-white tilapia by mutation of hps4 using CRISPR/Cas9 gene editing of a target site in exon 2. Homozygous mutation of hps4 led to a truncated protein of only 80 amino acids. Disruption of HPS4 led to a significant decrease (even absence at the adult stage) of melanophores and melanin, and a significant increase of iridophores, xanthophores and erythrophores. A sub-group of melanophores, even though very few in number, was found in the early embryonic stages. White iridophores without iridescence, hypertrophic xanthophores, and erythrophores with plenty of pigments were detected in the scales and caudal fins of the mutants, indicating enrichment of guanine, pteridine and carotenoids. To our knowledge, this is the first report on disruption of HPS4 in teleosts, and the first report demonstrating that HPS4 regulates iridophore, xanthophore and erythrophore numbers. Hps4 plays a fundamental role in LROs (lysosome-related organelles) -pigment development, melanophore survival and melanin biosynthesis. Our hps4 mutants provide a new model for studies of HPS4 function in vertebrates, and might be used as new germplasm for aquaculture.

Progressive pulmonary fibrosis in a murine model of Hermansky-Pudlak syndrome

BackgroundHPS-1 is a genetic type of Hermansky-Pudlak syndrome (HPS) with highly penetrant pulmonary fibrosis (HPSPF), a restrictive lung disease that is similar to idiopathic pulmonary fibrosis (IPF). Hps1ep/ep (pale ear) is a naturally occurring HPS-1 mouse model that exhibits high sensitivity to bleomycin-induced pulmonary fibrosis (PF). Traditional methods of administering bleomycin as an intratracheal (IT) route to induce PF in this model often lead to severe acute lung injury and high mortality rates, complicating studies focusing on pathobiological mechanisms or exploration of therapeutic options for HPSPF.MethodsTo develop a murine model of HPSPF that closely mimics the progression of human pulmonary fibrosis, we investigated the pulmonary effects of systemic delivery of bleomycin in Hps1ep/ep mice using a subcutaneous minipump and compared results to oropharyngeal delivery of bleomycin.ResultsOur study revealed that systemic delivery of bleomycin induced limited, acute inflammation that resolved. The distinct inflammatory phase preceded a slow, gradually progressive fibrogenesis that was shown to be both time-dependent and dose-dependent. The fibrosis phase exhibited characteristics that better resembles human disease with focal regions of fibrosis that were predominantly found in peribronchovascular areas and in subpleural regions; central lung areas contained relatively less fibrosis.ConclusionThis model provides a preclinical tool that will allow researchers to study the mechanism of pulmonary fibrosis in HPS and provide a platform for the development of therapeutics to treat HPSPF. This method can be applied on studies of IPF or other monogenic disorders that lead to pulmonary fibrosis.

Lung Transplantation for Pulmonary Fibrosis Associated With Hermansky-Pudlak Syndrome. A Single-center Experience.

Background.Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by oculocutaneous albinism, platelet storage defect with resultant bleeding diathesis, and pulmonary fibrosis. The bleeding diathesis associated with HPS had long been considered a contraindication to lung transplantation; consequently, few reports of successful lung transplantation for HPS exist.Methods.In the largest case series on lung transplant for HPS, we describe the characteristics of 11 lung transplant candidates with HPS-related pulmonary fibrosis, and the management and outcomes of 7 patients who underwent lung transplantation.Results.Of the 7 patients transplanted, 30-d survival was 85.7% (6/7). Six patients had at least 2 y of follow-up available with a 1-y survival of 83.3% and a 2-y survival of 83.3% (5/6). The median age at referral was 48 y (range 29–62 y). Eight patients (72.7%) were of Puerto Rican ancestry with confirmed type 1 HPS mutation. Six out of 7 patients received prophylaxis for bleeding diathesis, with a majority receiving desmopressin; 1 patient was administered aminocaproic acid infusion, and another received 2 units of platelets before surgery. Estimated blood loss and the amount of intraoperative blood product administered was highly variable with or without prophylaxis. Median blood loss was 400 mL (range 125–750) and estimated blood products administered was 700 mL (range 490–4043).Conclusions.HPS should not be considered a contraindication for lung transplantation. Although patients with HPS seem to have an increased risk of massive hemorrhage, the risk is unpredictable. Transplant teams should prepare a preoperative plan in consultation with hematology and consider the use of prophylactic platelet transfusion and desmopressin.

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

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. To study circumcision bleeding rates in male subjects who were diagnosed later in life with delta-storage pool deficiency (δ-SPD). We retrospectively reviewed the medical records of male subjects (≤18years 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. 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 2days (range: 1day to 4months). 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.

HPS6 Regulates the Biogenesis of Weibel-Palade Body in Endothelial Cells Through Trafficking v-ATPase to Its Limiting Membrane.

The Weibel–Palade body (WPB) is one of the lysosome-related organelles (LROs) in endothelial cells, whose main content is von Willebrand factor (vWF). The biogenesis of LROs is regulated by the Hermansky–Pudlak syndrome (HPS) protein-associated complexes through transporting cargo proteins to WPBs. Our previous studies have shown that HPS6, a subunit of BLOC-2 complex, is likely involved in the maturation of WPBs. However, the underlying mechanism remains unknown. In this study, we found that the knockdown of HPS6 in human umbilical vein endothelial cells (HUVECs) resulted in misshaped WPBs, decreased WPB number, and impaired vWF tubulation, which are similar to the characteristics of HPS6-deficient mouse endothelial cells. We observed similar morphological changes of WPBs in HUVECs after the knockdown of ATP6V0D1 (a subunit of v-ATPase). Furthermore, we found that HPS6 interacted with ATP6V0D1, suggesting that HPS6 transports ATP6V0D1 to the WPB limiting membrane for the assembly of the v-ATPase complex to maintain its acidic luminal pH, which is critical for the formation of vWF tubules during WPB maturation. In conclusion, HPS6 likely regulates the biogenesis of WPBs by participating in the trafficking of v-ATPase to the WPB membrane.

Clinical exome sequencing for diagnosing severe cryptogenic liver disease in adults: A case series.

Liver diseases remain unexplained in up to 30% of adult patients; genetic analysis could help establish the correct diagnosis. In six adult patients with cryptogenic liver disease, we performed whole-exome sequencing (WES) and evaluated the individual predisposition to progressive fatty liver disease by polygenic risk scores (PRS). In one patient, WES was allowed to diagnose the Hermansky-Pudlak syndrome. In the other two patients, genetic variants in LDLRAP1/MSH6 and ALDOB genes were identified, contributing to explaining the clinical presentation and disease pathogenesis (50% diagnostic uptake). In the other three patients, rare variants with a high likelihood of disrupting protein function in APOB, ATP7B, ABCB4 and ATP8B1 were identified. One patient who developed hepatocellular carcinoma during the follow-up had a high PRS value. The study supports the role of WES, combined with risk stratification by PRS and accurate clinical assessment in improving the diagnosis and informed management in patients with cryptogenic liver disease, a positive family history or severe fatty liver not fully accounted for by environmental triggers.

New insights into the pathogenesis of Hermansky–Pudlak syndrome

Hermansky-Pudlak syndrome (HPS) is characterized by defects of multiple tissue-specific lysosome-related organelles (LROs), typically manifesting with oculocutaneous albinism or ocular albinism, bleeding tendency, and in some cases with pulmonary fibrosis, inflammatory bowel disease or immunodeficiency, neuropsychological disorders. Eleven HPS subtypes in humans and at least 15subtypes in mice have been molecularly identified. Current understanding of the underlying mechanisms of HPS is focusing on the defective biogenesis of LROs. Compelling evidences have shown that HPS protein-associated complexes (HPACs) function in cargo transport, cargo recycling, and cargo removal to maintain LRO homeostasis. Further investigation on the molecular and cellular mechanism of LRO biogenesis and secretion will be helpful for better understanding of its pathogenesis and for the precise intervention of HPS.

The Microscopy-Based Assay to Study and Analyze the Recycling Endosomes using SNARE Trafficking.

Recycling endosomes (REs) are tubular-vesicular organelles generated from early/sorting endosomes in all cell types. These organelles play a key role in the biogenesis of melanosomes, a lysosome-related organelle produced by melanocytes. REs deliver the melanocyte-specific cargo to premature melanosomes during their formation. Blockage in the generation of REs, observed in several mutants of Hermansky-Pudlak syndrome, results in hypopigmentation of skin, hair, and eye. Therefore, studying the dynamics (refer to number and length) of REs is useful to understand the function of these organelles in normal and disease conditions. In this study, we aim to measure the RE dynamics using a resident SNARE STX13.

Genotypic and Phenotypic Spectrum of Foveal Hypoplasia: A Multicenter Study

To characterize the genotypic and phenotypic spectrum of foveal hypoplasia (FH). Multicenter, observational study. A total of 907 patients with a confirmed molecular diagnosis of albinism, PAX6, SLC38A8, FRMD7, AHR, or achromatopsia from 12 centers in 9 countries (n= 523) or extracted from publicly available datasets from previously reported literature (n= 384). Individuals with a confirmed molecular diagnosis and availability of foveal OCT scans were identified from 12 centers or from the literature between January 2011 and March 2021. A genetic diagnosis was confirmed by sequence analysis. Grading of FH was derived from OCT scans. Grade of FH, presence or absence of photoreceptor specialization (PRS+ vs. PRS-), molecular diagnosis, and visual acuity (VA). The most common genetic etiology for typical FH in our cohort was albinism (67.5%), followed by PAX6 (21.8%), SLC38A8 (6.8%), and FRMD7 (3.5%) variants. AHR variants were rare (0.4%). Atypical FH was seen in 67.4% of achromatopsia cases. Atypical FH in achromatopsia had significantly worse VA than typical FH (P < 0.0001). There was a significant difference in the spectrum of FH grades based on the molecular diagnosis (chi-square= 60.4, P < 0.0001). All SLC38A8 cases were PRS- (P= 0.003), whereas all FRMD7 cases were PRS+ (P < 0.0001). Analysis of albinism subtypes revealed a significant difference in the grade of FH (chi-square= 31.4, P < 0.0001) and VA (P= 0.0003) between oculocutaneous albinism (OCA) compared with ocular albinism (OA) and Hermansky-Pudlak syndrome (HPS). Ocular albinism and HPS demonstrated higher grades of FH and worse VA than OCA. There was a significant difference (P < 0.0001) in VA between FRMD7 variants compared with other diagnoses associated with FH. We characterized the phenotypic and genotypic spectrum of FH. Atypical FH is associated with a worse prognosis than all other forms of FH. In typical FH, our data suggest that arrested retinal development occurs earlier in SLC38A8, OA, HPS, and AHR variants and later in FRMD7 variants. The defined time period of foveal developmental arrest for OCA and PAX6 variants seems todemonstrate more variability. Our findings provide mechanistic insight into disorders associated with FHand have significant prognostic and diagnostic value.

Hermansky-Pudlak Syndrome: Identification of Novel Variants in the Genes HPS3, HPS5, and DTNBP1 (HPS-7).

Hermansky-Pudlak syndrome (HPS), a rare heterogeneous autosomal recessive disorder, is characterized by oculocutaneous albinism (OCA) and a bleeding diathesis due to a defect regarding melanosomes and platelet delta (δ)-granule secretion. Interestingly, patients with HPS type 2 (HPS-2) or HPS type 10 (HPS-10) present additionally with an immunological defect. We investigated three patients (IP1, IP2, and IP3) who suffer from a bleeding diathesis. Platelet aggregometry showed impaired platelet function and flow cytometry revealed a severely reduced platelet CD63 expression hinting to either a defect of platelet delta granule secretion or a decreased number of delta granules in these patients. However, only IP3 presents with an apparent OCA. We performed panel sequencing and identified a homozygous deletion of exon 6 in DTNBP1 for IP3. Western analysis confirmed the absence of the encoded protein dysbindin confirming the diagnosis of HPS-7. Interestingly, this patient reported additionally recurrent bacterial infections. Analysis of lymphocyte cytotoxicity showed a slightly reduced NK-degranulation previously documented in a more severe form in patients with HPS-2 or HPS-10. IP1 is carrier of two compound heterozygous variants in the HPS3 gene (c.65C > G and c.1193G > A). A homozygous variant in HPS5 (c.760G > T) was identified in IP2. The novel missense variants were classified as VUS (variant of uncertain significance) according to ACMG guidelines. For IP1 with the compound heterozygous variants in HPS3 a specialized ophthalmological examination showed ocular albinism. HPS3 and HPS5 encode subunits of the BLOC-2 complex and patients with HPS-3 or HPS-5 are known to present with variable/mild hypopigmentation.

Case series on Silvery Hair Syndromes: Single Center Experience.

Background:Silvery Hair Syndromes (SHS), an autosomal recessive inherited disorder, includes Chediak–Higashi syndrome (CHS), Griscelli syndrome (GS), Hermansky–Pudlak syndrome (HPS), and Elejalde syndrome. Associated immunological and neurological defects and predilection for hemophagocytic lymphohistiocytosis (HLH) makes them a distinctive entity in pediatric practice. Thorough clinical examination, bedside investigations such as peripheral blood smear (PBS) and hair microscopy, and bone marrow (BM) examination are inexpensive and reliable diagnostic tools.Methods:We report 12 cases with SHS (CHS, n = 06; GS, n = 04; HPS, n = 02).Results:8 out of 12 SHS children (CHS-05, GS-03) presented with HLH. Out of 5 cases of CHS with HLH, 2 died, 3rd is stable post-chemotherapy; 4th completed chemotherapy, underwent matched related hematopoietic stem cell transplant (HSCT), and is stable 8 months off treatment. The 5th child completed chemotherapy and is in process of transplant. One CHS child without HLH is thriving without any treatment. Of the 4 GS cases, 3 presented with HLH and received chemotherapy (HLH 2004 protocol). One lost follow-up after initial remission; another had recurrence 7 months off treatment and discontinued further treatment. The third child had recurrence 1.5 years after initial chemotherapy; HLH 2004 protocol was restarted followed by HSCT from matched sibling donor; is currently well, 2.5 years post-transplant. One child with GS had neurological features with no evidence of HLH and did not take treatment. Of 2 children with HPS, one presented with severe sepsis and the other with neurological problems. They were managed symptomatically.Conclusion:In SHS with HLH, chemotherapy followed by allogeneic hematopoietic stem cell transplantation is a promising curative option.

Histopathological Features of Monogenic Inflammatory Bowel Disease: Subanalysis of Systematic Review.

Histopathological Features of Monogenic Inflammatory Bowel Disease: Subanalysis of Systematic Review.

Eyelash trichomegaly: a systematic review of acquired and congenital aetiologies of lengthened lashes.

Long eyelashes have been popularized and many commercially available products exist to achieve eyelash growth as a desired cosmetic effect. Eyelash trichomegaly may be induced by medications, procedures, or be related to medical conditions; however, the exact mechanisms that govern eyelash growth are not well elucidated. This study aims to identify and summarize aetiologies associated with eyelash trichomegaly. We report a systematic review of 148 clinical trials, prospective and retrospective studies, and case reports describing all evidence-based potential aetiologies of eyelash trichomegaly obtained from the Medline/PubMed and Cochrane Library through January 2021. Inclusion criteria were defined as (i) human studies involving congenital and acquired diseases in which eyelash trichomegaly is a characteristic or (ii) assessment of trichomegaly as an adverse or desired effect of a medication or procedure. Exclusion criteria included: animal studies, articles not available in English, outcomes unrelated to eyelash trichomegaly, and secondary review articles. Pharmacologic agents associated with eyelash trichomegaly included prostaglandin analogues (15-keto fluprostenol isopropyl ester, bimatoprost, latanoprost, and travoprost), epidermal growth factor receptor inhibitors (cetuximab, erlotinib, and panitumumab), interferon-alpha, and calcineurin inhibitors (tacrolimus and cyclosporine). Surgical procedures of the eyelid, as well as allergic rhinitis, atopic dermatitis, HIV, ichthyosis vulgaris (IV), uveitis, and vernal keratoconjunctivitis were also associated with increased eyelash growth. Congenital disorders associated with lengthened eyelashes included Cantú syndrome, CHOPS syndrome, Coffin-Siris syndrome, congenital heart disease, Cornelia de Lange syndrome, Costello syndrome, familial trichomegaly, Floating Harbor syndrome, Hermansky-Pudlak syndrome, Kabuki-Makeup syndrome, KBG syndrome, Oliver-McFarlane syndrome, Rubinstein-Taybi syndrome, and Smith-Magenis syndrome. While the most common cause of eyelash trichomegaly is topical bimatoprost use, better understanding of pathways implicated in eyelash trichomegaly may lead to the discovery of additional medications to stimulate eyelash growth and create avenues for future therapeutic interventions.

A Role of Phosphatidylserine in the Function of Recycling Endosomes.

Cells internalize proteins and lipids in the plasma membrane (PM) and solutes in the extracellular space by endocytosis. The removal of PM by endocytosis is constantly balanced by the replenishment of proteins and lipids to PM through recycling pathway. Recycling endosomes (REs) are specific subsets of endosomes. Besides the established role of REs in recycling pathway, recent studies have revealed unanticipated roles of REs in membrane traffic and cell signalling. In this review, we highlight these emerging issues, with a particular focus on phosphatidylserine (PS), a phospholipid that is highly enriched in the cytosolic leaflet of RE membranes. We also discuss the pathogenesis of Hermansky Pudlak syndrome type 2 (HPS2) that arises from mutations in the AP3B1 gene, from the point of view of dysregulated RE functions.

Two Novel Homozygous HPS6 Mutations (Double Mutant) Identified by Whole-Exome Sequencing in a Saudi Consanguineous Family Suspected for Oculocutaneous Albinism.

Background: Oculocutaneous albinism (OCA) is an autosomal recessive disorder of low or missing pigmentation in the eyes, hair, and skin. Multiple types of OCA, including Hermansky-Pudlak syndrome 6 (HPS6), are distinguished by their genetic cause and pigmentation pattern. HPS6 is characterized by OCA, nose bleeding due to platelet dysfunction, and lysosome storage defect. To date, 25 disease-associated mutations have been reported in the HPS6 gene. Methods: DNA was extracted from proband, and whole-exome sequencing (WES) was performed using the Illumina NovaSeq platform. Bioinformatic analysis was done with a custom-designed filter pipeline to detect the causative variant. We did Sanger sequencing to confirm the candidate variant and segregation analysis, and protein-based structural analysis to evaluate the functional impact of variants. Result: Proband-based WES identified two novel homozygous mutations in HPS6 (double mutation, c.1136C>A and c.1789delG) in an OCA suspect. Sanger sequencing confirmed the WES results. Although no platelet and/or lysosome storage defect was detected in the patient or family, an oculocutaneous albinism diagnosis was established based on the HPS6 mutations. Structural analysis revealed the transformation of abnormalities at protein level for both nonsense and frameshift mutations in HPS6. Conclusion: To the best of our knowledge, the double mutation in HPS6 (p.Ser379Ter and p.Ala597GlnfsTer16) represents novel pathogenic variants, not described previously, which we report for the first time in the Saudi family. In silico analyses showed a significant impact on protein structure. WES should be used to identify HPS6 and/or other disease-associated genetic variants in Saudi Arabia, particularly in consanguineous families.

Hermansky–Pudlak Syndrome Type 6 Accompanied with Bowel Vascular Malformation: Clinical Case

Background. Hermansky–Pudlak syndrome type 6 is rare hereditary disease caused by pathogenic variants in base sequence, deletions, and insertions in the HPS6 gene encoding the transmembrane protein of the same name. This disease occurs with hemorrhagic syndrome, oculocutaneous albinism, and inflammatory bowel diseases (in some cases). The clinical picture of the disease, including the gastrointestinal tract pathology, has not been studied completely due to the syndrome rarity.Clinical case description. We would like to present the description of clinical case of the patient with Hermansky–Pudlak syndrome type 6 accompanied with bowel vascular malformation. The patient diagnosed with “oculocutaneous albinism” at the age of 4.5 has shown recurrent intestinal bleedings, blood hemoglobin concentration decrease to 45 g/l; platelet count, mean platelet volume and platelet distribution width remained within the reference values. Slight decrease of Quick’s value to 68% (normal range 70–120%) was revealed. The study of platelet morphology has revealed a decrease in the number of dense granules: &lt; 3 in 25% platelets, &lt; 6 — in 64%. Ultrasound investigation has revealed signs of vascular malformation in ascending colon: significant changes of diameter (widening) and shape of intestinal wall vessels. Molecular genetic analysis (NGS) has revealed the nucleotide variant c.1133T&gt;G (p.Leu378Arg) in homozygous state in the HPS6 gene. The same variant in homozygous state was revealed in the younger proband sister who also had vascular changes in the ascending colon wall.Conclusion. Differential diagnosis of Germanic–Pudlak syndrome type 6 should be performed with other types of this syndrome as well as with syndrome and non-syndrome forms of oculocutaneous albinism. Molecular genetic confirmation of the diagnosis is suggested via massive parallel sequencing (NGS) methods (exome sequencing included) due to the rarity of Hermansky–Pudlak syndrome.

An Interesting Case of Hermansky Pudlak Syndrome- A Rare Case Report

Oculo cutaneous albinism [OCA] is a autosomal recessive disorder associated with reduction in the pigment of skin, hair and eyes with strabismus and nystagmus leading to misrouting of optic nerve fibers from eye to brain during development. Reduction in skin pigmentation leads to the increased risk of skin cancer due to photosensitivity. They can occur in isolated forms or associated with syndromes. Syndromic OCA includes oculocutaneous albinism with hermansky pudlak syndrome. Seven types of OCA [1-6] with mutation in different genes have been identified.

Surgery-Associated Bleeding Risk in Patients with Platelet Function Disorders - a Cross Sectional Study with the American Thrombosis and Hemostasis Network Dataset (ATHNdataset)

▪Introduction: Platelet function disorders (PFDs) are a group of heterogenous bleeding disorders with varying bleeding phenotype. Intraoperative and post-operative bleeding are serious complications among patients with PFDs undergoing surgery. There are very few studies in literature that have specifically investigated surgery associated bleeding complications in PFDs. The aim of this study was to utilize a large national dataset to describe surgeries performed in patients with PFD, characterize the bleeding associated with these surgical procedures and outline the therapeutic approaches adopted.Methods: In this retrospective study, the ATHNdataset was queried for demographic data, PFD diagnosis, surgeries among patients with PFD, intraoperative and post-operative bleeding episodes and treatment. Descriptive statistics were used. The ATHNdataset captures information from patients with bleeding and clotting disorders from over 140 federally funded hemophilia and thrombosis treatment centers (HTCs) in the US. Patients authorize inclusion of their demographic and clinical information in this de-identified Health Insurance Portability and Accountability Act (HIPAA)-compliant data set.Results: From January 2010 to March 2020, the ATHNdataset captured 2767 patients with PFDs, of which 1769 (63.93%) were female and 998 (36.1%) were male, with 1393 patients between 0-18 years (50%) and 1374 (50%) adults >18 years. PFDs identified include 32 patients with Bernard Soulier syndrome (1.16%), 131 patients with Glanzmann thrombasthenia (4.7%), 4 patients with Gray platelet syndrome (0.14%), 29 patients with Hermansky Pudlak syndrome (1%), 1548 patients with storage pool deficiency (55.9%), and 1023 patients diagnosed as PFD (36.9%). A total of 3252 procedures were reported between 2010 and 2020; 1271 patients (46%) patients with at least one documented procedure. Figure 1 shows common procedures among patients with PFDs.Surgery-associated bleeding episodes (includes intraoperative and post-operative bleeds) were reported with 69 procedures (2.1%), which included intraoperative bleeds reported for 18 procedures (0.5%) and post-operative bleeds reported for 51 procedures (1.6%). Of the 60 procedures in patients with Glanzmann thrombasthenia, surgery-associated bleeding episodes were reported after 9 dental procedures (41%), 1 circumcision (25%) and 11 other surgeries/procedures (18.3%). Of the 6 procedures in patients with Bernard Soulier syndrome, no intraoperative or post-operative bleeding episodes were reported. Of 1688 procedures in patients with storage pool deficiency, surgery-associated bleeding episodes were reported after 26 dental procedures (1.5%) and 62 other surgeries/procedures (3.67%). No intraoperative or post-operative mortality was reported among these patients.Of 1272 patients who underwent at least 1 procedure, 646 patients (50.7%) received some form of treatment before/during/after a procedure. Among these 646 patients, 2794 exposure days of hemostasis medications were used before/during/after procedures. Among these, 49% were prior to the procedure, 0.7 % during the procedure and 49.5% after the procedure. Treatments used are shown in figure 2.Conclusion: Our study shows that patients with PFDs have a substantial risk of bleeding associated with surgery. Identifying the risk of bleeding by type and providing appropriate pre-surgical prophylaxis can decrease rates of surgery-associated bleeding in PFDs. [Display omitted] DisclosuresSidonio: Sanofi, Takeda, Octapharma, Bayer, Biomain, Grifols, Kedrion, Genentech. Catalyst, Guardian Therapeutics, Novo Nordisk, Hema Biologics, Uniqure.: Consultancy, Honoraria. Ahuja: Genentech: Membership on an entity's Board of Directors or advisory committees; Takeda: Other: DSMB member ; XaTek, Inc: Patents & Royalties; Sanofi: Membership on an entity's Board of Directors or advisory committees.

Introducing a Novel Biophysical Platelet Function Panel to Investigate Disorders of Primary Hemostasis and Bleeding of Unknown Cause

A subset of patients with chronic bleeding remain undiagnosed even after extensive diagnostic evaluation are labeled as “bleeding of unknown cause” (BUC). The key barrier to treating these patients is that they have a clinical bleeding tendency in the presence of normal diagnostic tests, and optimal methods for monitoring and treating patients with BUC remain unknown. While patients with BUC have symptoms of a primary hemostatic disorder, there is no diagnostic test or biomarker that can accurately identify which patients are at risk for bleeding such as those with mild Von Willebrand Disease (VWD) which comprise a broad spectrum of patients with varying degrees of bleeding. In order to fill this diagnostic gap in disorders of primary hemostasis, there is a clinical need for more assays of platelet function.To that end, we have engineered multiple new biophysical assays to assess disorders of primary hemostasis and apply this panel of platelet function testing to potentially define new bleeding disorders, characterize platelet phenotypes in patients with BUC, and refine the definition of mild VWD. Our panel of platelet function tests (Fig 1) collectively enables us to simultaneously assess different facets of primary hemostasis from the microscopic level of single-platelet physiology to hemostatic plug formation, thereby capturing various aspects of platelet function with a single blood sample. Our platelet function panel ranges from platelet adhesion and bulk clot contraction assays to spatially-regulated platelet granule secretion assay, single-platelet contraction cytometry, microfluidics, and a microengineered vascularized bleeding model. As such, we are leveraging these biophysical assays to correlate platelet function with bleeding phenotype severity and establish the dynamic range of this diagnostic panel. We have now established that our assays can be utilized to study blood samples from patients with disorders including hemophilia A, Hermansky-Pudlak Syndrome, FLI-1 mutation, and sickle cell disease among others (Fig 2), demonstrating the clinical utility of our platelet function panel.Our panel can also be used to assess the effects of novel therapeutics on different aspects of platelet function simultaneously. To investigate how crizanlizumab (p-selectin inhibitor) affects hemostatic plug formation, healthy human blood was treated with crizanlizumab. Platelet α-granule secretion enables exposure of P-selectin, and with crizanlizumab we observed restricted platelet filopodial extension and diminished α-granule exocytosis, and an overall decrease in adhered platelets to the fibrinogen micropattern (Fig 3A). The adhesion assay demonstrated a decrease in spreading and adhesion of platelets to collagen and fibrinogen with treatment (Fig 3B). Using the bleeding model, hemostasis was achieved within the normal established range and platelets contracted normally. This suggests that p-selectin has a limited role in the setting of minor injury. Utilizing the bulk contraction assay, we exhibited increased contraction early in clot formation, however over time the treated platelets contracted similarly to the control (Fig 3C). Interestingly, the effect of crizanlizumab-induced restriction of filopodial extension did not correlate with impaired bulk clot contraction or time to form hemostatic plug. Our work suggests crizanlizumab affects platelet spreading at the single-cell level but does not impair platelet function in achieving primary hemostasis at the whole blood level.Here we demonstrate the translational utility of our platelet function panel in providing a deeper understanding of platelet biophysics as it relates to hematologic conditions, with implications for investigation to include pharmaceutical applications. The versatility of this novel panel in capturing platelet function from single-platelet contraction to providing in vitro models with the bleeding device provides multiple dimensions to platelet investigation for primary hemostatic disorders and BUC that have not yet been elucidated. Ongoing research is being conducted using our comprehensive platelet function panel to investigate platelet properties in BUC and mild VWD and correlate these biophysics with bleeding phenotypes. Using this approach we aim to provide novel diagnostic testing with clinical relevance for disorders that have been incompletely characterized until now. [Display omitted] DisclosuresMeeks: National Institutes of Health: Research Funding; Hemophilia of Georgia: Research Funding; National Hemophilia Foundation: Research Funding; Spark Therapeutics: Consultancy; Sangamo Therapeutics: Consultancy; Pfizer: Consultancy; Sanofi: Consultancy; CSL Behring: Consultancy; Genentech: Consultancy; Takeda: Consultancy. Lam: Sanguina, Inc.: Current holder of individual stocks in a privately-held company.