Samuel de Souza Medina

A longitudinal evaluation of anti-FVIII antibodies demonstrated IgG4 subclass is mainly correlated with high-titre inhibitor in haemophilia A patients

The development of inhibitory antibodies against factor VIII (FVIII) (inhibitor) is the major complication in haemophilia A patients. The FVIII‐binding antibodies development comprises a polyclonal immunoglobulin (Ig) G response. Recent studies showed strong correlation between the presence of neutralizing anti‐FVIII antibodies (inhibitors) and IgG4 subclass. The aim of this study was to evaluate anti‐FVIII IgG subclasses in haemophilia A patients with inhibitor both in a cross‐sectional and in a longitudinal analysis. Inhibitors were determined by Nijmegen–Bethesda assay. Anti‐FVIII IgG subclasses were performed by ELISA, and samples from 20 healthy individuals were used to validate the test. We studied 25 haemophilia A patients with inhibitor, previously treated exclusively with plasma‐derived FVIII concentrates or bypassing agents. The IgG subclasses distributions were evaluated in two groups of patients classified according to inhibitor response. IgG1 and IgG4 antibodies were most prominent in haemophilia A patients with inhibitors when compared with IgG2 and IgG3. This study reports for the first time the behaviour of FVIII‐binding IgG1 and IgG4 subclasses in a longitudinal analysis, in a clinical setting, of high‐response inhibitor haemophilia A patients, showing the correlation of IgG4 and the inhibitor titres. In spite of being considered a non‐pathologic antibody subclass with anti‐inflammatory properties in other situations, IgG4 is correlated with the presence of high‐titre inhibitor in the haemophilia setting. The comprehension of the IgG4 role in immune response may be crucial to establish the process for designing specific tolerance to FVIII.

Heat treatment of samples improve the performance of the Nijmegen-Bethesda assay in hemophilia A patients undergoing immune tolerance induction.

Nijmegen-Bethesda assay is the gold standard to assess inhibitory antibodies against factor (F) VIII. This method has some limitations, including high coefficient of variation and possible interference of residual endogenous or exogenous factor VIII. Heat-treatment of samples at 56 °C for 30 min could be a strategy to improve the sensitivity of this test. The aim of this study was to compare inhibitor quantification in hemophilia patients with and without inhibitor performed in previously heated and non-heated samples. A total of 109 analyses from 46 patients with severe hemophilia A were performed. Patients were divided into three groups: 20 patients with no history of inhibitor, recently and not recently exposed to FVIII (group I), 21 patients with history of inhibitor not exposed to FVIII (group II), and 5 patients (68 samples) undergoing an immune tolerance induction (ITI) protocol (group III). For patients with no history of inhibitor, heat-treatment did not modify the results (p=0.24). However, differences in inhibitor levels between heated and non-heated samples were observed in patients with history of inhibitor (group II, p<0.05) and in patients in ITI (group III, p<0.001). In 11 samples, inhibitor quantification shifted from negative to positive. Additionally, a longitudinal evaluation of each ITI patient showed similar trend line for the results of heated and non-heated samples. In this study, we demonstrated that heating samples increase sensitivity of Nijmegen-Bethesda assay, with no shift from negative to positive results in patients with no history of inhibitor. Furthermore, this procedure has an important role to patients undergoing an ITI protocol.

Platelet associated IgG may be related with thrombocytopenia in patients with myelodysplastic syndromes.

Thrombocytopenia is common in patients with myelodysplastic syndromes (MDS) and immune destruction of platelets could be an important factor for its occurrence. We prospectively analyzed platelet-associated IgG (PAIgG) through platelet immunofluorescence test (PIFT), mean platelet volume (MPV), platelet size deviation width (PDW) and glycocalicin index (GCI) of 54 patients with MDS, classified according to the International Prognostic Scoring System (IPSS). Thrombocytopenia (platelet count<100×10(9)/L) was correlated with a higher amount of PAIgG, significantly higher MPV and increased GCI. In addition, worse prognosis IPSS groups were associated with a higher positivity of PIFT, which could be indicative of advanced disease.

Evaluation of the immature platelet fraction contribute to the differential diagnosis of hereditary, immune and other acquired thrombocytopenias

The differential diagnosis of immune (ITP) and hereditary macrothrombocytopenia (HM) is key to patient management. The immature platelet fraction (IPF) represents the subset of circulating platelets with higher RNA content, and has been shown to distinguish hypo- from hyperproliferative thrombocytopenias. Here we evaluated the diagnostic accuracy of IPF in the differential diagnosis between HM and other thrombocytopenias in a population of patients with post-chemotherapy thrombocytopenia (n = 56), bone marrow failure (n = 22), ITP (n = 105) and HM (n = 27). TPO levels were also measured in HM and ITP matched for platelet counts. Platelet counts were similar in all patient groups. Higher IPF values were observed in both ITP (12.3%; 2.4–65.6%) and HM (29.8%; 4.6–65.9%) compared to hypoproliferative thrombocytopenias. IPF values were also higher in HM compared to ITP, yielding a diagnostic accuracy of 0.80 (95%CI 0.70–0.90; P < 0.0001) to distinguish these two conditions. Intra- and inter-assays reproducibility of IPF in HM patients revealed that this is a stable parameter. In conclusion, IPF is increased in HM compared to both ITP and other thrombocytopenias and contributes to the differentiation between ITP and HM. Further studies are warranted to understand the biological rationale of these findings and to its incorporation in diagnostic algorithms of HM.

Thalidomide for the treatment of gastrointestinal bleeding due to angiodysplasia in a patient with Glanzmann’s thrombasthenia

Angiodysplasia is a frequent cause of persistent gastrointestinal (GI) hemorrhage in elderly patients. Although GI bleeding isn’t the most common manifestation in patients with bleeding disorders, when present, it represents a challenging complication. We describe a 62-year-old patient with Glanzmann’s thrombasthenia, who used thalidomide for severe and recurrent GI bleeding. For 6 months, the patient experienced temporary control of GI bleeding with thalidomide in a daily oral dose of 100 mg. The anti-angiogenic effects of thalidomide have recently been explored by several groups, particularly in the management of bleeding from angiodysplasia, including cases with von Willebrand disease. Here, we review the relevant descriptions of the use of thalidomide in this situation, and also discuss potential reasons why we observed only a temporary control of the GI bleeding in our patient, such as the use of low-dose regimen due to limitations posed by thalidomide side effects.

Zika virus and inherited bleeding disorders

Zika virus (ZIKV) outbreaks, first in the Pacific region in 2007 and later on South America and Caribe in 2015 have established ZIKV as an important emerging pathogen. Emerging pathogens are defined as appearance of new infectious agents in a population or as pathogens that have long existed, but are presenting a rapid increase in either incidence or geographic range [1]. These pathogens constitute a challenge in the context of blood supply safety. This editorial aims to discuss the risk of ZIKV transmission among those with inherited bleeding disorders who may require transfusion of blood components or administration of plasma-derived products. Inherited bleeding disorders are characterized by haemorrhagic episodes, which are usually treated with replacement therapy. Despite the great advances achieved in haemophilia treatment, including recombinant and modified clotting factors, and currently the use of plasma-derived factor VIII and factor IX concentrates produced using highly effective pathogen removal/inactivation technologies, many patients worldwide are still reliant on fresh frozen plasma (FFP) and cryoprecipitate. Nonetheless, for other rare bleeding disorders, such as factor V deficiency and certain inherited platelet disorders, transfusions of FFP and platelet concentrates, respectively, are still the mainstay of treatment [2,3]. Over the last decades, the risk of blood-borne pathogens transmission through transfusion of blood products triggered the development of an increasingly safer blood supply. Strategies include the improvement of donor selection programmes, the use of highly sensitive screening methods for human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), application of more effective procedures of pathogen removal/inactivation and development of biotechnology for the expression of recombinant proteins [4]. Despite all these advances, a remaining risk of pathogen transmission is still present, and highly serious in the case of cellular blood products. Zika virus epidemiology

Intermittent low platelet counts hampering diagnosis of X-linked thrombocytopenia in children: report of two unrelated cases and a novel mutation in the gene coding for the Wiskott-Aldrich syndrome protein

BackgroundThrombocytopenia can occur in different circumstances during childhood and although immune thrombocytopenia is its most frequent cause, it is important to consider other conditions, especially when there is a persistent or recurrent low platelet count. We report two cases of intermittent thrombocytopenia, previously misdiagnosed as immune thrombocytopenia.Cases presentationBoth cases described were boys who presented with an intermittent pattern of thrombocytopenia, with a persistently low mean platelet volume. In both patients, peripheral blood smear revealed small platelets and flow cytometry showed low expression of Wiskott-Aldrich syndrome protein (WASP) in leucocytes. Molecular analysis of the first case identified a mutation in exon 2 of the gene coding for WASP, leading to a p.Thr45Met amino acid change and confirming the diagnosis of X-linked thrombocytopenia. In the second case, a novel missense mutation in exon 2 of the gene coding for WASP was detected, which resulted in a p.Pro58Leu amino acid change.ConclusionThese two rare presentations of thrombocytopenia highlight the importance of evaluating the peripheral blood smear in the presence of recurrent or persistent thrombocytopenia and show that failing to do so can lead to misdiagnoses. Since thrombocytopenia may be found in pediatric outpatient clinic, increased awareness among general pediatricians will help to improve the differential diagnosis of this condition.

Allergic reaction in a cohort of haemophilia A patients using plasma‐derived factor VIII (FVIII) concentrate is rare and not necessarily triggered by FVIII

In contrast to haemophilia B, allergic manifestations are rare complications in haemophilia A (HA) patients treated with factor VIII (FVIII) concentrates. Nevertheless, it can be serious and hamper replacement therapy in these cases. The aims of this study were to evaluate the frequency of allergic reaction in a cohort of HA patients treated only with plasma‐derived FVIII (pdFVIII) concentrates, and assess the possible immune mechanisms involved. History of allergic reaction was retrospectively assessed. Patients with allergic manifestations were followed, and had plasma samples collected in different timepoints in relation to the allergic episode. These samples were analysed for the presence of inhibitor and anti‐FVIII immunoglobulins subclasses. Three of 322 HA patients (0.9%) developed allergic reaction after exposure to pdFVIII products during the last 15 years in our centre. The first patient, with severe HA, without inhibitor, had anti‐pdFVIII IgE and IgG4, but no anti‐recombinant FVIII (rFVIII) IgE. The second patient, with severe HA, and high‐responding inhibitor, presented allergic manifestation with both, pdFVIII concentrate and activated prothrombin complex concentrate. Although anti‐pdFVIII and anti‐rFVIII IgG4 were detected, no anti‐FVIII IgE was present. The third patient, with moderate HA without inhibitor, atopic, had no anti‐FVIII immunoglobulin detected, and allergic symptoms disappeared after switching to rFVIII concentrate. This study corroborates the low incidence of allergic reactions in HA patients. In the three cases presented, the anti‐FVIII immunoglobulin profile demonstrated that the allergic manifestation was triggered by other proteins contained in pdFVIII products, and not directed to FVIII.