Haemophilia care in Asia: Learning from clinical practice in some Asian countries.

BACKGROUND: The healthcare systems in Asia vary greatly due to the socio-economic and cultural diversities which impact haemophilia management. METHODS: An advisory board meeting was conducted with experts in haemophilia care from Asia to understand the heterogeneity in clinical practices and care provision in the region. FINDINGS: The overall prevalence of haemophilia in Asia ranges between 3 and 8.58/100,000 patients. Haemophilia A was more prevalent as compared to haemophilia B with a ratio of around 5:1. There is under-diagnosis in the region due to lack of diagnosis, registries and/or lack of appropriate facilities in suburban areas. Most patients are referred to the haematologists by their families or primary care physicians, while some are identified during bleeding episodes. Genetic testing faces obstacles like resource constraints, services available at limited centres and unwillingness of patients to participate. Prophylaxis is offered for people with haemophilia (PWH) with a severe bleeding phenotype. Recombinant factors are approved in most countries across the region and are the preferred therapy. The challenges highlighted for not receiving a high standard of care include patients' reluctance to use an intravenous treatment, poor patient compliance due to frequency of infusions, budget constraints and lack of funding, insurance, availability and accessibility of factor concentrates. Prevalence of neutralizing antibodies ranged from 5% to 20% in the region. Use of immune tolerance induction and bypassing agents to treat inhibitors depends on their cost and availability. CONCLUSION: Haemophilia care in Asia has evolved to a great extent. However, some challenges remain for which a strategic approach along with multi-stakeholder involvement are needed.

Cost and effectiveness comparison of sirolimus versus standard treatment in Kasabach-Merritt phenomenon: a real-world evidence study in Thailand.

The conventional treatment of Kasabach-Merritt Phenomenon (KMP) consists of corticosteroids with vincristine/vinblastine or others. The aim of the study is to compare the first-year direct costs and effectiveness between sirolimus and conventional treatment. A retrospective case-control study of KMP patients was conducted at a mean age of 9 months (1 day to 12 years) between 2000 and 2022 from four tertiary centers in Thailand. The direct costs, hematologic and clinical complete response (HCR, CCR), hospitalization, length of stay, and complications were compared. Of 29 patients, 13 underwent sirolimus (four upfront and nine were refractory to the conventional). The first-year total cost had no statistically significant difference between sirolimus VS conventional treatment (8,852.63 VS 9,083.56 USD: p value: 0.94). The therapeutics achievement was the same in both HCR (244.75 VS 168.94 days; p value: 0.60) and CCR (419.77 VS 399.87 days; p value: 0.90). The subgroup analysis of the first-line sirolimus (n = 4) compared with the conventional (n = 25) showed a more reduced total cost (4,907.84 VS 9,664.05 USD; p value: 0.26) rendered net total cost of -4,756.21 USD per patient (cost saving). A more significant contrast of therapeutic achievement by reduction of both HCR (11.67 VS 224.20 days; p value: 0.36) and CCR (38.50 VS 470.88 days; p value: 0.04) was shown. The sirolimus had no difference in hospitalization, length of stay, and complications. Even though, it was unable to identify significant differences in cost-effectiveness. Sirolimus is suitable for all patients who have diagnosis of KMP either for rescue therapy or first-line treatment.

Germline HAVCR2 mutations and their relation to the clinical spectrum of subcutaneous panniculitis-like T-cell lymphoma and hemophagocytic lymphohistiocytosis: results from a multicenter study and meta-analysis.

Germline HAVCR2 mutations are frequently detected in subcutaneous panniculitis-like T-cell lymphoma (SPTCL) patients with/without hemophagocytic lymphohistiocytosis (HLH) but factors associated with variable manifestations remain undetermined. To evaluate clinical variations and associated factors in SPTCL and/or HLH with/without HAVCR2 mutations, we performed direct sequencing of HAVCR2 exon 2 using DNA from patients with SPTCL or idiopathic HLH/HLH-like systemic illnesses, defined by HLH alone without secondary causes. The systematic review and individual patient data (IPD) level meta-analysis which included the present and previously published studies reporting HAVCR2 mutations in SPTCL with/without HLH populations was subsequently conducted using random-effects meta-analysis and multivariate logistic regression. Among 34 patients enrolled, ten of 28 SPTCL patients developed HLH/HLH-like systemic illnesses. Six cases with HAVCR2Y82C mutation manifested with HLH without panniculitis. Male sex (P=0.03) and age <18 years (P=0.04) were associated with HLH, corresponding to the inverse correlation between age and HLH-2004 score (r=-0.40; P=0.02). Homozygous HAVCR2Y82C mutation was more common in the presence of HLH compared with the absence (75.0% vs. 44.4%; P=0.02). Using IPD from the present and the other three eligible cohorts (N=127), male sex, heterozygous and homozygous/compound heterozygous HAVCR2 mutations were associated with HLH by the adjusted odds ratio of 2.93 (95% confidence interval [CI]: 1.22-7.06), 4.77 (95% CI: 1.05-21.63) and 8.48 (95% CI: 2.98-24.10), respectively. Patients with male sex and/or germline HAVCR2 mutations showed an increased risk of developing HLH. Younger patients tended to manifest with HLH, while older patients typically presented with SPTCL with less frequent HLH/HLH-like systemic illnesses.

Clinical outcomes of low-dose pharmacokinetic-guided extended half-life versus low-dose standard half-life factor VIII concentrate prophylaxis in haemophilia A patients.

INTRODUCTION: Despite receiving standard half-life (SHL) factor VIII (FVIII) concentrates prophylaxis, some severe haemophilia A (HA) patients still encounter spontaneous breakthrough bleeding. Individualized pharmacokinetic (PK)-guided dosing of extended half-life (EHL) FVIII concentrates may reduce their bleeding events. AIM: To compare clinical outcomes before and after switching low-dose prophylaxis using weight-based SHL FVIII to PK-guided EHL FVIII concentrates, taking into consideration of a trough FVIII activity at 1 IU/dl above natural baseline. METHODS: In this single-centre prospective cohort, Thai severe or moderate HA (FVIII activity ≤3 IU/dl) patients receiving low-dose weight-based SHL FVIII prophylaxis were enrolled. After a 3-day wash-out period, participants underwent low-dose EHL FVIII prophylaxis with PK-based adjustment (myPKFiT® ) for 6 months. The annualized bleeding rates (ABR), the annualized joint bleeding rates (AJBR), the haemophilia-specific quality-of-life (Haemo-QoL or Haemo-QoL-A) scores, the Hemophilia Joint Health Scores (HJHS) and the annualized FVIII consumption were compared between the two prophylactic periods. RESULTS: Of 15 eligible subjects (mean age 18.7 ± 6.7 years), ABR, AJBR and HJHS were significantly reduced (mean differences of -11.1 ± 4.9 bleeds/year, -10.4 ± 5.2 joint bleeds/year and -5.1 ± 1.5 marks, respectively; P < .001 for all comparisons) after switching regimen. The quality-of-life scores had also improved (P = .001). Nonetheless, FVIII consumption tended to increase despite no statistical significance (means of 1240.9 ± 531.3 SHL FVIII IU/kg/year versus 1591.7 ± 438.9 EHL FVIII IU/kg/year; P = .05). CONCLUSIONS: This is the first low-dose, PK-guided, EHL FVIII prophylaxis clinical study in Thailand. Benefits and practicability of this personalized regimen may support the implementation of regular FVIII prophylaxis in developing countries with budget constraints. CLINICALTRIALS: gov NCT05281185.

Phase 2 study of nilotinib in pediatric patients with Philadelphia chromosome-positive chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is rare in children and accounts for ≤15% of all myeloid leukemia cases. When we initiated this study with nilotinib, imatinib was the only tyrosine kinase inhibitor indicated for pediatric patients with Philadelphia chromosome-positive (Ph+) CML in chronic phase (CP); alternative treatment options were needed, particularly for patients who developed resistance or intolerance (R/I) to imatinib. This phase 2 study enrolled pediatric patients with either Ph+ CML-CP R/I to imatinib or dasatinib or newly diagnosed Ph+ CML-CP. Data presented are from analyses with minimum follow-up of up to 24 cycles (1 cycle is 28 days). Fifty-nine patients with Ph+ CML-CP were enrolled, and 58 were treated (R/I, n = 33; newly diagnosed, n = 25). Major molecular response (MMR) rate at cycle 6 in the R/I cohort was 39.4% (primary end point); 57.6% of patients achieved or maintained MMR and 81.8% achieved or maintained complete cytogenetic response (CCyR) by 24 cycles. In patients with newly diagnosed disease, rates of MMR by cycle 12 and CCyR at cycle 12 were 64.0% each (primary end points); by cycle 24, cumulative MMR and CCyR rates were 68.0% and 84.0%, respectively. The safety profile of nilotinib in pediatric patients was generally comparable with the known safety profile in adults, although cardiovascular events were not observed in this study, and hepatic laboratory abnormalities were more frequent; no new safety signals were identified. In summary, nilotinib demonstrated efficacy and a manageable safety profile in pediatric patients with Ph+ CML-CP. This trial was registered at www.clinicaltrials.gov as #NCT01844765.

MYH9 disorder: Identification and a novel mutation in patients with macrothrombocytopenia.

The diagnosis of MYH9 disorder is guided by recognizing granulocyte Döhle body-like inclusion bodies and large/giant platelets in the peripheral blood smear. Immunofluorescence study of nonmuscle myosin heavy chain IIA is a sensitive screening method for diagnosis of MYH9 disorder. The diagnosis can then be confirmed by genetic analysis. A total of 67 patients with macrothrombocytopenia were included, of which 11 patients (16%), aged 4 months to 22 years, were ultimately diagnosed with MYH9 disorder. One novel mutation in exon 30 at c.4338T>C (p.F1446A) was detected. This mutation was associated with nonhematologic manifestations presenting in late adolescence with cataracts, hearing loss, and hematuria.

Dermatologic manifestations in pediatric patients after liver and HSCT: A 20-year retrospective cohort study.

LT and HSCT are now potentially curative treatments for many medical conditions. Dermatologic manifestations are one of the sequelae after transplantation. To study the prevalence and associated risk factors of dermatologic manifestations after pediatric LT and HSCT. A 20-year retrospective cohort study was conducted in children, aged ≤15 years, who received LT or HSCT from January 1, 1997, to December 31, 2017. Medical records were reviewed for data collection until December 31, 2018. A total of 70 LT and 51 HSCT recipients were included. The percentages of overall dermatologic manifestations after LT and HSCT were 64.3% and 64.7%, respectively. Viral infection was the most common manifestation in both groups, with mucocutaneous HSV infection as the most prevalent. One HSCT recipient developed leukemia cutis. GVHD was revealed in 27.5% of HSCT recipients. Impetigo and xerosis were significantly observed in patients using azathioprine and prednisolone. Approximately two-thirds of pediatric LT and HSCT recipients experienced dermatologic manifestations, potentially associated with immunosuppressive agents. Thus, regular skin examination and optimized immunosuppression would be beneficial in these recipients.

Subcutaneous Panniculitis-like T-Cell Lymphoma With Hemophagocytic Lymphohistiocytosis Syndrome in Children and Its Essential Role of HAVCR2 Gene Mutation Analysis.

BACKGROUND: We identified 3 adolescents with alpha-beta subtype subcutaneous panniculitis-like T-cell lymphoma. CASE PRESENTATION: Three patients presented with prolonged fever, abnormal skin lesions, and cytopenia described in the context. All had the same disease entity, which showed the prolonged duration of B systemic symptoms till diagnosis, difficulty to distinguish from autoimmune diseases, presence of hemophagocytic lymphohistiocytosis syndrome, good response, and remained on long-term remission with nonchemotherapy treatment, which included oral corticosteroid and cyclosporin. CONCLUSIONS: Although diagnosis can only be "highly suspected" with pathologic review, some cases may need multiple serial skin biopsy to clarify diagnosis because of the discrete distribution of specific histology. T-cell receptor gene rearrangement, which demonstrates a monoclonal pattern of alpha and beta chain gene, is the essential requirement for specific diagnosis. The role of molecular analysis by identification of germline hepatitis A virus cellular receptor 2 (HAVCR2) gene mutation can be much valuable in classifying susceptible patients.

A Study to Assess and Improve Adherence to Iron Chelation Therapy in Transfusion-Dependent Thalassemia Patients.

Transfusion-dependent thalassemia (TDT) patients require regular blood transfusions. The unavoidable consequence is iron overload. Iron chelation therapy is the mainstay of treatment, of which the favorable outcome depends mainly on adherence level. The aim of this study was to assess adherence to iron chelation therapy of TDT patients. A cross-sectional cohort of TDT patients were evaluated on their adherence to chelation therapy using the Thai version of Morisky Medication Adherence Scales (MMAS-8). A total of 70 patients (38 males, 32 females), with a median age of 10 years, were enrolled in the study. Sixteen patients (22.9%) and 54 patients (77.1%) were classified as high and medium-low adherence level groups. The raised serum ferritin value for 6 months previous to enrollment in the high adherence level group is lower than the medium-low adherence level group (276.4 vs. 413.0 ng/mL, p = 0.034, respectively). Factors impacted high adherence to iron chelation including younger age (p = 0.015) and deferasirox (DFX) administration (p = 0.025). The body weight and height in both groups were not statistically different. The most common obstacle to adherence was forgetfulness. The Thai version of MMAS-8 is a practical tool for evaluating adherence to chelation therapy in TDT patients. High adherence level of patients correlates with more controlled serum ferritin level. The younger age and once-daily dose chelation therapy are associated with better adherence.

Pediatric primary central nervous system tumors registry in Thailand under National Health Security Office schemes.

BACKGROUND: Few epidemiological studies of pediatric central nervous system (CNS) tumors have been performed using data from Southeast Asian national registries. Therefore, we aimed to examine data on CNS tumors from the first national childhood CNS tumor registry in Thailand. METHODS: Newly diagnosed children with benign and malignant primary CNS tumors from 20 nationwide hospitals were included. Two eras in the Thai registry were studied to compare national protocol effectiveness, including 2003-2005 (before establishment of a pediatric CNS tumor protocol) and 2011-2012 (post-establishment). RESULTS: The first study period had 300 patients with an incidence of 7.5/1,000,000 person-years and the second had 168 patients with an incidence of 13.24/1,000,000 person-years. The three most common tumors were gliomas, medulloblastoma/primitive neuroectodermal tumor (PNET), and germ cell tumors. The most common tumor site was the cerebellum, followed by the brainstem and pineal region. Five- and 10-year overall survival (OS) rates were 46.62% (95% confidence interval [CI] 40.85-52.18) and 41.78% (95% CI 36.11-47.34), respectively, for the first period. The second period had a 5-year OS of 64.75% (95% CI 56.70-71.68). OS rates for gliomas, germ cell tumors, medulloblastoma/PNET, and ependymomas were better in the second period than in the first period. CONCLUSIONS: The incidence of primary childhood CNS tumors in our study is lower compared with other reports. Improvement of OS in the second study period might be because of establishment of the Thai Pediatric Oncology Group, and national protocols for childhood CNS tumors.

Clinical outcomes and prognostic factors to predict treatment response in high risk neuroblastoma patients receiving topotecan and cyclophosphamide containing induction regimen: a prospective multicenter study.

BACKGROUND: Neuroblastoma is the most common extra-cranial solid tumor among children. Despite intensive treatment, patients with advanced disease mostly experience dismal outcomes. Here, we proposed the use of topotecan and cyclophosphamide containing induction regimen as an upfront therapy to high risk neuroblastoma patients. METHODS: Patients with high risk neuroblastoma undergoing ThaiPOG high risk neuroblastoma protocol from 2016 to 2017 were studied. All patients received 6 cycles of induction regimen consisting of 2 cycles topotecan (1.2 mg/m2/day) and cyclophosphamide (400 mg/m2/day) for 5 days followed by cisplatin (50 mg/m2/day) for 4 days combined with etoposide (200 mg/m2/day) for 3 days on the third and fifth cycles and cyclophosphamide (2100 mg/m2/day) for 2 days combined with doxorubicin (25 mg/m2/day) and vincristine (0.67 mg/m2/day) for 3 days on the fourth and sixth cycles. Treatment response after the 5th cycle before surgery and treatment-related toxicities after each topotecan containing induction cycle were evaluated. Relevant prognostic factors were analyzed to measure the treatment response among those patients. RESULTS: In all, 107 high risk neuroblastoma patients were enrolled in the study. After the 5th cycle of induction regimen, the patients achieved complete response (N = 2), very good partial response (N = 40), partial response (N = 46) and mixed response (N = 19). None of the patients experienced stable disease or disease progression. The most significant prognostic factor was type of healthcare system. The most common adverse effect was febrile neutropenia followed by mucositis, diarrhea and elevated renal function. CONCLUSION: The topotecan and cyclophosphamide containing induction regimen effectively provides favorable treatment response. The regimen is well tolerated with minimal toxicity among patients with high risk neuroblastoma in Thailand.

Novel mutations in Thai patients with glanzmann thrombasthenia.

OBJECTIVES: Glanzmann thrombasthenia (GT) is an autosomal recessive platelet disorder, caused by defects of the platelet integrin αIIbß3 (GPIIb/IIIa) resulting from pathogenic mutations in either ITGA2B or ITGB3. It is characterized by spontaneous mucocutaneous bleeding. The molecular features of GT in Thailand have not been identified. This study aimed to determine the clinical and molecular features of unrelated Thai patients with GT. METHODS: Four patients with clinically suspected GT were recruited at the Division of Pediatric Hematology/Oncology, King Chulalongkorn Memorial Hospital. The diagnosis was based on clinical and hematological parameters as well as genetic analysis. Whole exome sequencing (WES) was performed in all cases. RESULTS: Of the four patients studied, the median age at first suspicion of GT was 2.5 years. All presented with severe bleeding symptoms (WHO bleeding scale 3). Flow cytometry to assess the surface GPIIb/IIIa complex showed reduced expression. By WES, we successfully identified seven mutant alleles in ITGA2B. One alteration, the c.2915dup (p.Leu973Alafs*63), was detected in two unrelated families. One patient was homozygous for the c.617T>A (p.Val206Asp). Of the five different mutations, three have never been previously described. These include a missense, c.617T>A (p.Val206Asp), a deletion, c.1524_1533del (p.Gln508Hisfs*3), and a nonsense, c.2344C>T (p.Arg782Ter). CONCLUSION: This study reported three novel mutations expanding the genotypic spectrum of ITGA2B causing GT.

Adrenal insufficiency in non-transfusion-dependent α-thalassemia.

BACKGROUND: Very few studies about adrenal insufficiency (AI) have been published with regard to non-transfusion-dependent (NTD) thalassemia, and none of those studies involved α-thalassemia patients. The aim of this study was therefore to determine the prevalence of AI in patients with NTD α-thalassemia, and to identify factors that predict the development of AI in this thalassemia subpopulation. METHODS: This cross-sectional descriptive study was conducted in NTD α-thalassemic children at three referral hospitals in Thailand in 2015-2016. Preliminary screening for AI was done using the 1 µg adrenocorticotropic hormone (ACTH) stimulation test. Suspected AI was then confirmed on insulin tolerance test (ITT). AI was defined as peak cortisol <18 µg/dL. AI was categorized as either primary or secondary AI according to peak ACTH. RESULTS: Thirty patients with NTD α-thalassemia were included in this study. Ten of 25 patients (40%) had abnormal initial screening. Eight of nine (88.9%) who underwent ITT were confirmed as having AI. No patients diagnosed with AI had any clinical symptoms of AI. The percentage of primary and secondary AI (n = 8) was 25% and 75%, respectively. Mean age and mean hemoglobin level showed a trend toward being associated with AI (P = 0.98). CONCLUSION: The prevalence of biochemical AI in α-thalassemia patients was similar to rates previously reported for NTD ß-thalassemia. Annual screening for AI in α-thalassemia patients is recommended, and glucocorticoid replacement should be considered in NTD α-thalassemia patients with AI during critical illness.

Eltrombopag for children with chronic immune thrombocytopenia (PETIT2): a randomised, multicentre, placebo-controlled trial.

BACKGROUND: The thrombopoietin receptor agonist eltrombopag has been shown to be safe, tolerable, and effective for adults with chronic immune thrombocytopenia. We aimed to investigate the safety and efficacy of eltrombopag for children with chronic immune thrombocytopenia. METHODS: PETIT2 was a two part, randomised, multicentre, placebo-controlled study done at 38 centres in 12 countries (Argentina, Czech Republic, Germany, Hong Kong, Israel, Italy, Russia, Spain, Taiwan, Thailand, UK, and USA). Paediatric patients aged 1-17 years who had chronic immune thrombocytopenia and platelet counts less than 30 × 10(9) per L were randomly assigned (2:1) to receive eltrombopag or placebo. We stratified patients by age into three cohorts (patients aged 12-17 years, 6-11 years, and 1-5 years) before randomly entering them into a 13 week, double-blind period. Randomisation was done by the GlaxoSmithKline Registration and Medication Ordering System and both patients and study personnel were masked to treatment assignments. Patients who were allocated eltrombopag received tablets (except for those aged 1-5 years who received an oral suspension formulation) once per day for 13 weeks. Starting doses for patients aged 6-17 were based on bodyweight, and ethnic origin and ranged between 50 mg/day and 25 mg/day (starting dose for patients aged 1-5 years was 1·2 mg/kg/day or 0·8 mg/kg/day for east Asian patients). Patients who completed the double-blind period entered a 24 week open-label treatment period in which all patients received eltrombopag at either the starting dose (if they were formerly on placebo) or their established dose. The primary outcome was the proportion of patients achieving platelet counts of at least 50 × 10(9) per L in the absence of rescue therapy for 6 or more weeks from weeks 5 to 12 of the double-blind period. The intention-to-treat population included in the efficacy assessment consisted of all patients who were randomly assigned to one of the treatment groups, and the safety population included all patients who received at least one dose of study drug. This trial is registered with ClinicalTrials.gov, number NCT01520909. FINDINGS: Beginning in March 15, 2012, 92 patients were enrolled, and the trial was completed on Jan 2, 2014. 63 patients were assigned to receive eltrombopag and 29 were assigned to receive placebo. In the double-blind period, three patients discontinued treatment because of adverse events: two patients in the eltrombopag group withdrew because of increased liver aminotransferases and one in the placebo group withdrew because of abdominal haemorrhage. 25 (40%) patients who received eltrombopag compared with one (3%) patient who received placebo achieved the primary outcome of platelet counts of at least 50 × 10(9) per L for 6 of the last 8 weeks of the double-blind period (odds ratio 18·0, 95% CI, 2·3-140·9; p=0·0004). Responses were similar in all cohorts (eltrombopag vs placebo: 39% vs 10% for patients aged 12-17 years, 42% vs 0% for patients aged 6-11 years, and 36% vs 0% for patients aged 1-5 years). Proportionately fewer patients who received eltrombopag (23 [37%] of 63 patients) had WHO grades 1-4 bleeding at the end of the double-blind period than did those who received placebo (16 [55%] of 29 patients); grades 2-4 bleeding were similar (three [5%] patients who received eltrombopag vs two [7%] patients who received placebo). During the 24-week open-label treatment period, 70 [80%] of 87 patients achieved platelet counts of 50 × 10(9) per L or more at least once. Adverse events that occurred more frequently with eltrombopag than with placebo included nasopharyngitis (11 [17%] patients), rhinitis (10 [16%] patients), upper respiratory tract infection (7 [11%] patients), and cough (7 [11%] patients). Serious adverse events occurred in five (8%) patients who received eltrombopag and four (14%) who received placebo. Safety was consistent between the open-label and double-blind periods. No deaths, malignancies, or thromboses occurred during the trial. INTERPRETATION: Eltrombopag, which produced a sustained platelet response in 40% of patients with chronic immune thrombocytopenia, is a suitable therapeutic option for children with chronic symptomatic immune thrombocytopenia. We identified no new safety concerns and few patients discontinued treatment because of adverse events. FUNDING: GlaxoSmithKline.

HEMOSTATIC STUDIES IN DENGUE PATIENTS.

The pathogenesis of hematologic changes in dengue patients is not clearly understood. Consistent hematological findings include vasculopathy, thrombocytopenia, and coagulopathy. There are evidences suggesting that dengue virus causes pathophysiological changes that involve all of the consistent hematologic findings resulting in vasculopathy, reduction in platelet number as well as platelet dysfunction, and reduction of several coagulation factors. Laboratory evidences of disseminated intravascular coagulation (DIC) are also demonstrated in all degrees of severity in dengue patients. Only in severe dengue cases is profound DIC aggravated, leading to uncontrolled bleeding and death. A study to determine the extent of the activation of endothelial cells and the hemostatic system in correlation with clinical severity and also to detect the best prognostic factor for severe dengue showed plasma von Willebrand factor antigen (VWF:Ag) to be the best indicator of progression to severe dengue.