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Pharmacokinetic Studies, Assessing the Efficiency of FVIII/VWF Concentrates and Intravenous Human Immunoglobulin, Revealed the Etiopathogenesis of Acquired von Willebrand Disease in Patient With MGUS

2024; Wiley; Linguagem: Inglês

10.1111/hae.15137

1365-2516

C. Miele, Francesca D’Auria, Luca Manfredi, Paolo Conca, Ernesto Cimino, Rosaria Mormile, Stefania De Simone, Olga Scudiero, Marcella Savoia, Antonella Tufano, Matteo Nicola Dario Di Minno, F. Capasso, Cristina Mazzaccara,

Blood disorders and treatments

Acquired von Willebrand Syndrome (AVWS) is a rare disorder characterized by a bleeding diathesis, with symptoms ranging from mild to severe. It differs from the congenital von Willebrand disease (vWD) due to the absence of personal and family history of haemorrhagic disorders, a late-onset bleeding tendency and the frequent association with haematological malignancies, autoimmune or cardiovascular diseases [1, 2]. Amongst lymphoproliferative disorders, monoclonal gammopathy of undetermined significance (MGUS) is the most frequently reported condition associated with AVWS, accounting for approximately 23% of all cases, according to the International Registry of the Subcommittee on von Willebrand factor [3]. In this regard, clinical attention should be given to most haematologic, malignant, and autoimmune disorders, with serum protein electrophoresis and a complete blood count being crucial to screen for monoclonal gammopathy and other haematologic disorders, respectively [4]. Despite the multiple pathophysiological mechanism involved, treatments for AVWS are focused on the eradication of the underlying disease, control of acute episodes and prevention of bleeding events, especially in high-risk situations, such as during surgery. Desmopressin (DDAVP), plasma-derived FVIII/VWF concentrates, antifibrinolytic, high-dose IVIG (Intravenous Immunoglobulin) and plasmapheresis are some of the therapeutic measures taken for this purpose [4]. Despite the multiple pathophysiological mechanisms that interfere with the normal functionality of the VWF molecule in AVWS, patients with MGUS can exhibit the presence of circulating autoantibodies directed against both functional and non-functional domains of VWF [5]. The pathogenesis of these antibodies encompasses: the presence of circulating antibodies neutralizing platelet-related domains of VWF (Inhibitors) or antibodies forming immuno-complexes with VWF, that are rapidly cleared from the circulation by the reticulo-endothelial systems (non-neutralizing antibodies) [6]. Since the presence of inhibitors is often associated with a more severe haemorrhagic phenotype, laboratory investigations can be challenging trying to distinguish between the two immunological mechanisms [6, 7]. Mixing studies and enzyme-linked immunosorbent assays (ELISA) are both suitable methods to identify the etiopathogenetic mechanism of these antibodies. However, since ELISA test is intricate and has not yet been adequately standardized, it is an option not yet fully utilized in haemostasis laboratories [6]; at the same time, the sole use of the mixing test can only confirm or exclude the presence of neutralizing antibodies, but does not allow the identification of antibodies increasing the clearance of the VWF. Here we report a case of AVWS secondary to MGUS IgG λ associated to the presence of non-neutralizing antibodies, whose etiopathogenic mechanism was identified with the help of pharmacokinetic and mixing studies. Our patient was a 73-year-old woman who referred to Regional Reference Center of Coagulation Disorders of Federico II University Hospital, Naples (Italy), following a massive post-operative haemorrhage embroiling the surgery site of a robotic cholecystectomy procedure due to cholelithiasis. No relevant haemorrhagic events were reported in family or personal medical history, apart from a recent haemothorax arisen after tracheal intubation subsequent to a hysterectomy with bilateral salpingo-oophorectomy procedure. Given her older age, the recent history of two bleeding events and the lack of previous bleeding diathesis, we suspected an acquired bleeding syndrome. In agreement with this hypothesis, we researched for a possible underlying pathology that triggered this bleeding episode. Serum protein electrophoresis studies revealed a peak in the gamma zone of the IgG λ type, probably associated to an underlying monoclonal gammopathy (data not showed). The complete blood count showed low levels of erythrocytes (3.46 × 106/µL; r.v.), haemoglobin (10.80 g/dL; r.v. 12.0–15.5) and haematocrit (31.10 %; r.v. 4.0–5.0) while leukocyte and platelet counts were within the normal range. As showed in Table 1, first level haemostasis assays, highlighted a prolongation of activated Partial Thromboplastin Time (aPTT), with normal Prothrombin Time (PT) and Fibrinogen levels. Mixing study using an equal volume of citrated patient plasma with a normal pool plasma, showed an aPTT value within the normal range, suggesting a factor deficiency as a cause of the prolonged aPTT, thus acquired haemophilia A (AHA) and antiphospholipid antibody syndrome (APS) were ruled out. Subsequently, factors VIII, IX, XI and XII were measured, displaying results within reference range, except for low FVIII levels (Table 1). Following these results and the patient's clinical history, the AVWS was strongly suspected and the specific VWD tests, such as VWF:Ag, VWF:RiCof and VWF:CB were measured, showing a substantial reduction (Table 1). To elucidate the pathogenetic mechanism underlying the VWF defect affecting our patient, both mixing studies at 37°C for 2 h and pharmacokinetic analysis were performed to confirm the nature of anti-VWF antibodies. In our patient, we demonstrate non-neutralizing antibody-mediated VWF clearance as the mechanism accountable for AVWS. Mixing studies showed no inhibitory effect on normal plasma for VWF:RiCof, VWF:CB and FVIII:C levels, consistent probably with antibodies against non-functional VWF domains, enabling us to rule out the presence of neutralizing antibodies (inhibitors) (Table 2). Pharmacokinetic studies with FVIII/von Willebrand factor concentrate and IVIG, confirmed the suspicion of an acquired form of vWD, highlighting the incomplete recovery of FVIII:C, VWF:Ag, VWF:RiCof, and VWF:CB levels, after the administration of FVIII/VWF concentrates with a short-lived increase in plasma VWF levels related to the presence of anti-VWF antibodies (Figure S1A). On the other hand, 1 g/kg high-dose IVIG for 2 days demonstrated a significant improvement in all parameters related to VWF levels after both the first and second infusions (Figure S1B), confirming the presence of non-neutralizing autoantibodies accelerating the clearance of circulating VWF due to the formation of immunocomplexes and their elimination through the reticuloendothelial system. This corroborates what is already widely reported about IVIG being an essential therapeutic instrument for the management of AVWS, particularly for IgG MGUS related cases [8, 9]. The exact mechanisms of action through which IVIG reduces the clearance of circulating VWF in IgG MGUS are not fully understood; however, they may involve the inhibition of pathogenic VWF antibodies or B-cell receptors by transfused anti-idiotype antibodies, the blocking of macrophage Fc receptors, and/or the activation of the complement system [10]. The aim of this study was to demonstrate how, by utilizing the mixing test and pharmacokinetic studies, it is possible to define the etiopathogenesis of anti-VWF antibodies and thus confirm the presence of non-neutralizing antibodies even when the ELISA test is not available. This approach has been crucial because, in the absence of a standardized ELISA assay, able to identify non-neutralizing VWF antibodies, relying only on mixing studies could fail to recognize an AVWS, given the normalization of aPTT, FVIII:C, VWF:Ag, VWF:RiCof and VWF:CB, especially in a routine laboratory. In this scenario, personal and family history, along with pharmacokinetic studies involving FVIII/VWF and high-dose IVIG, were found to be an excellent diagnostic tool for distinguishing between the two types of antibodies. The study limitation was the inability to evaluate vWF plasma clearance through the analysis of vWF multimers and the vWF propeptide, the latter being uncommon assays in haemostasis routine laboratory. In conclusion, our work confirmed that patients with AVWS associated with MGUS do not have a great recovery when using plasma-derived concentrates compared to IVIG. Even though they have different pharmacokinetic responses and effectiveness, the use of these medications played a pivotal role along with coagulation assay for framing the right etiopathogenesis and highlighted how the conversation between haematologists and laboratory experts is key for a proper diagnosis, given the challenging diagnostic workup in AVWS. Ciro Miele, Cristina Mazzaccara and Filomena Capasso conceived, designed and wrote the study; Francesca D'Auria, Sabrina De Simone, Luca Manfredi, Olga Scudiero and Marcella Savoia contributed to the management and collection of data; Rosaria Mormile, Paolo Conca, Ernesto Cimino, Antonella Tufano and Matteo Nicola Dario Di Minno provided advice on the study design and content. Cristina Mazzaccara, Ciro Miele, Antonella Tufano, Paolo Conca, Matteo Nicola Dario Di Minno and Filomena Capasso reviewed and edited the manuscript. All authors have read and agreed to the published version of the manuscript. Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The authors have no competing interests. All investigations were conducted according to the Declaration of Helsinki principles. Informed consent was obtained from patient included in this study. The authors state no conflict of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.