Changes in and significance of platelet function and parameters in Kawasaki disease

Platelets in Kawasaki disease: mediators of vascular inflammation

Kawasaki disease, a systemic vasculitis that affects young children and can result in coronary artery aneurysms, is the leading cause of acquired heart disease among children. A hallmark of Kawasaki disease is increased blood platelet counts and platelet activation, which is associated with an increased risk of developing resistance to intravenous immunoglobulin and coronary artery aneurysms. Platelets and their releasate, including granules, microparticles, microRNAs and transcription factors, can influence innate immunity, enhance inflammation and contribute to vascular remodelling. Growing evidence indicates that platelets also interact with immune and non-immune cells to regulate inflammation. Platelets boost NLRP3 inflammasome activation and IL-1β production by human immune cells by releasing soluble mediators. Activated platelets form aggregates with leukocytes, such as monocytes and neutrophils, enhancing numerous functions of these cells and promoting thrombosis and inflammation. Leukocyte-platelet aggregates are increased in children with Kawasaki disease during the acute phase of the disease and can be used as biomarkers for disease severity. Here we review the role of platelets in Kawasaki disease and discuss progress in understanding the immune-effector role of platelets in amplifying inflammation related to Kawasaki disease vasculitis and therapeutic strategies targeting platelets or platelet-derived molecules.

Platelet function in neonates and children

Platelets are major regulators of haemostasis and coagulation. The primary role of platelets in coagulation is to form a stable clot and stop bleeding. Studies of platelet phenotype and function in neonates and children have been restricted by the large volumes required for many common platelet function tests such as platelet aggregometry. Developmental changes in platelets have not been as well described as developmental changes in plasma coagulation proteins, and overall, platelet phenotype and function in neonates and children has been understudied when compared to adults. Recent developments in more sensitive platelet function testing methods requiring smaller blood volumes such as flow cytometry has enabled recent studies to further investigate platelet phenotype and function in neonates and children. In this review we will provide an overview of recent advances from the past five years in platelets in the context of developmental haemostasis, as well as the role of platelets in neonatal paediatric disease.

Serum amyloid A as a biomarker for immunoglobulin resistance in Kawasaki disease

BACKGROUND

Intravenous immunoglobulin (IVIG) resistance is of prime importance in Kawasaki disease (KD). In this study, we examined the value and mechanism of serum amyloid A (SAA) level in predicting IVIG resistance in patients with KD.

METHODS

SAA levels were measured in 497 consecutive patients with KD before IVIG therapy in the training set. The patients were divided into two groups (IVIG-responsive and IVIG-resistant) according to the American Heart Association (AHA) definition of IVIG resistance. Demographic, echocardiographic, and laboratory data were also retrospectively analyzed and tabulated to predict IVIG resistance. The predictive value of SAA was validated on test sets of prospective data. Cytokine microarrays were analyzed from 4 patients with resistant to IVIG, 4 patients with responsive to IVIG and 4 healthy volunteers.

RESULTS

During the training set, 409 patients with KD were enrolled, of whom 43 (10.5%) were resistant to initial IVIG treatment and 47 (11.49%) had coronary artery lesions (CALs). Serum levels of SAA were higher in the IVIG resistant group compared to the IVIG responsive group, (380.00 [204.40-547.25] vs 230.85 [105.40-490.00] mg/L; p = .008). The values of total bilirubin, C-reactive protein, neutrophils, alanine aminotransferase, aspartate aminotransferase, interleukin-6(IL-6), and procalcitonin were significantly higher in the IVIG-resistant group than in the IVIG-responsive group (p < .05); however, the lymphocytes, platelets, serum sodium levels, and duration of fever before IVIG therapy were significantly lower (p < .05). There was no significant difference in SAA levels between patients with KD with and without CALs. Binary logistic regression analysis showed that SAA (p = .008), neutrophils (p < .001), total bilirubin (p = .001), platelet count (p = .004), and serum sodium level (p = .019) were independent factors influencing IVIG resistance. The optimal cutoff value of SAA for IVIG resistance prediction was 252.45 mg/L, with a corresponding clinical sensitivity of 69.8% and specificity of 54.4%. Based on receiver operating characteristic (ROC) curve analyses, the area under the curve (AUC) of combined detection with these five indicators was 0.800, clinical sensitivity was 69.8%, and specificity was 76.2%. In the prospective data, the sensitivity, specificity, and accuracy of SAA for identifying IVIG resistance KD were 77.8%,69.0%, and 70.0%, respectively. Compared with IVIG- responsive group and healthy children, the levels of IL-6 was upregulated significantly in IVIG-resistant group through cytokine microarrays.

CONCLUSIONS

SAA may be a potential biomarker for predicting IVIG responsiveness to KD, Combined detection of SAA levels, total bilirubin, neutrophil count, platelet count, and serum sodium levels is superior to that of any other single indicator for predicting IVIG resistance in KD. And elevated SAA may accompany with IL-6 in KD patients, its use in clinical practice may be helpful for treatment management.

A machine learning model for distinguishing Kawasaki disease from sepsis

KD is an acute systemic vasculitis that most commonly affects children under 5 years old. Sepsis is a systemic inflammatory response syndrome caused by infection. The main clinical manifestations of both are fever, and laboratory tests include elevated WBC count, C-reactive protein, and procalcitonin. However, the two treatments are very different. Therefore, it is necessary to establish a dynamic nomogram based on clinical data to help clinicians make timely diagnoses and decision-making. In this study, we analyzed 299 KD patients and 309 sepsis patients. We collected patients' age, sex, height, weight, BMI, and 33 biological parameters of a routine blood test. After dividing the patients into a training set and validation set, the least absolute shrinkage and selection operator method, support vector machine and receiver operating characteristic curve were used to select significant factors and construct the nomogram. The performance of the nomogram was evaluated by discrimination and calibration. The decision curve analysis was used to assess the clinical usefulness of the nomogram. This nomogram shows that height, WBC, monocyte, eosinophil, lymphocyte to monocyte count ratio (LMR), PA, GGT and platelet are independent predictors of the KD diagnostic model. The c-index of the nomogram in the training set and validation is 0.926 and 0.878, which describes good discrimination. The nomogram is well calibrated. The decision curve analysis showed that the nomogram has better clinical application value and decision-making assistance ability. The nomogram has good performance of distinguishing KD from sepsis and is helpful for clinical pediatricians to make early clinical decisions.

Increased Myosin light chain 9 expression during Kawasaki disease vasculitis

Introduction

Kawasaki disease (KD) is an acute systemic vasculitis that predominantly afflicts children. KD development is known to be associated with an aberrant immune response and abnormal platelet activation, however its etiology is still largely unknown. Myosin light chain 9 (Myl9) is known to regulate cellular contractility of both non-muscle and smooth muscle cells, and can be released from platelets, whereas any relations of Myl9 expression to KD vasculitis have not been examined.

Methods

Plasma Myl9 concentrations in KD patients and children with febrile illness were measured and associated with KD clinical course and prognosis. Myl9 release from platelets in KD patients was also evaluated in vitro. Myl9 expression was determined in coronary arteries from Lactobacillus casei cell wall extract (LCWE)-injected mice that develop experimental KD vasculitis, as well as in cardiac tissues obtained at autopsy from KD patients.

Results and discussion

Plasma Myl9 levels were significantly higher in KD patients during the acute phase compared with healthy controls or patients with other febrile illnesses, declined following IVIG therapy in IVIG-responders but not in non-responders. In vitro, platelets from KD patients released Myl9 independently of thrombin stimulation. In the LCWE-injected mice, Myl9 was detected in cardiac tissue at an early stage before inflammatory cell infiltration was observed. In tissues obtained at autopsy from KD patients, the highest Myl9 expression was observed in thrombi during the acute phase and in the intima and adventitia of coronary arteries during the chronic phase. Thus, our studies show that Myl9 expression is significantly increased during KD vasculitis and that Myl9 levels may be a useful biomarker to estimate inflammation and IVIG responsiveness to KD.

Platelet parameters and the association with morbidity and mortality in Preterm Infants

BACKGROUND

There is growing recognition of the role of platelets in inflammation and immune responses, and platelets have been associated with various cardiovascular diseases. It is also known that neonatal morbidities are related to overall platelet activity, and platelet parameters may have the potential to predict morbidities and mortality in preterm infants. This study aimed to assess the initial platelet parameters and the association with major morbidities and mortality in preterm neonates.

METHODS

We retrospectively reviewed data from very preterm neonates with a gestational age (GA) <32 weeks who were admitted between June 2020 and May 2021 for platelet parameters (counts, mean platelet volume (MPV), platelet distribution width (PDW) and plateletcrit (platelet counts x MPV/10000(%)) at birth. Major morbidities included early- onset sepsis (EOS) ≤3 days after birth, severe intraventricular hemorrhage (IVH) grade ≥3, and early or overall mortality.

RESULTS

A total of 197 very preterm neonates were studied. Their mean (±SD) GA was 28.0 ± 2.4 weeks, birth weight was 990 ± 293 g, platelet counts were 245 ± 81 x1000/μL, MPV was 10.0 ± 0.7 fl, PDW was 11.0 ± 1.6 fl, and plateletcrit was 0.24 ± 0.08%. MPV had a weak negative correlation with both GA (r = -0.234, p = 0.001) and BW (r = -0.343, p <0.001). A lower plateletcrit was associated with EOS (0.14 (0.04-0.22) % vs. 0.23 (0.19-0.30) %, p = 0.027), severe IVH ≤7 days after birth (0.18 (0.14-0.27) % vs. 0.23 (0.20-0.30) %, p = 0.022), and early and overall mortality (0.15 (0.20-0.30) % vs. 0.23 (0.20-0.30) %, p = 0.049; 0.20 ± 0.09 % vs. 0.25 ± 0.07 %, p = 0.008).

CONCLUSION

A lower plateletcrit within 24 hours of birth was associated with EOS, severe IVH ≤7 days after birth, and first-week and overall mortality in very preterm neonates.

Predictive Role of IL-2R and IL-10 in the Anti-inflammatory Response and Antiplatelet Therapy of Kawasaki Disease: A Retrospective Study

To date, Kawasaki disease (KD) has only been able to be diagnosed and evaluated using clinical characteristics. Additionally, the therapeutic effect and cardiovascular complications could not be verified until its occurrence. The present retrospective study analyzed the dynamic alterations of inflammatory cytokines, platelet (PLT) count, and subgroups of lymphocytes, such as cluster of differentiation (CD) 8+ T cells and CD19+ B cells, under different conditions in 64 children with KD. The percentage distribution of lymphocyte subgroups and the altered neutrophil lymphocyte ratio demonstrated that the inflammatory response was dominated by the B cell-mediated humoral immune response before intravenous immunoglobulin (IVIG) treatment, but mainly by T cells via cellular cytotoxic effects after IVIG treatment. Among the different types of inflammatory cytokines, the results of the present study revealed that the altered levels of interleukin-2 receptor (IL-2R) and interleukin-10 (IL-10) were closely associated with the percentage of CD8+ T cells and CD19+ B cells. Additionally, the two cytokines exhibited more sensitive fluctuations based on the status of the children with KD in various circumstances compared with other indexes, such as the percentages of CD8+ T cells and CD19+ B cells or the PLT count. These results suggested that children with KD who are ≥4 years old may benefit from IVIG but will not benefit from decreased platelet activation or suffer less cardiovascular complications. Additionally, starting clopidogrel usage earlier as an antiplatelet strategy should be considered based on the observed continuous rise in the PLT count in children with KD receiving IVIG. In conclusion, dynamically monitoring the levels of IL-2R and IL-10 has the potential to provide indications of the intensity and development of the inflammatory response in children with KD and may contribute to the early prediction and adjustment of pathological and pharmacological effects of therapy.

Correct identification of incomplete Kawasaki disease

Incomplete Kawasaki disease (IKD) is characterized by a longer fever time, younger age of onset, and higher incidence of coronary artery disease compared with complete Kawasaki disease. Kawasaki disease is often difficult to diagnose early because of its incomplete clinical symptoms. This issue could delay treatment and harm the health of the child. This article reviews the clinical characteristics and pathogenesis of IKD to help clinicians understand the symptoms of IKD, make the correct diagnosis, and provide timely treatment.

Clinical characteristics of Kawasaki disease and concurrent pathogens during isolation in COVID-19 pandemic

BACKGROUND

The aim of this study is to explore the characteristics of Kawasaki disease (KD) and concurrent pathogens due to a stay-at-home isolation policy during coronavirus disease 2019 (COVID-19) epidemic.

METHODS

All patients with KD admitted between February and April in 2015-2020, were classified into before (group 1, in 2015-2019) and after (group 2, in 2020) isolation groups. A total of 4742 patients [with KD (n = 98) and non-KD (n = 4644)] referred to Mycoplasma pneumoniae (MP) and virus detection were analyzed in 2020. Clinical characteristics, laboratory data, and 13 pathogens were analyzed retrospectively.

RESULTS

Group 2 had a significantly increased incidence of KD (0.11%) with 107 patients compared to that of group 1 (0.03%) with 493 patients. The comparisons of oral mucosal change, strawberry tongue, desquamation of the fingertips, cervical lymphadenopathy and neutrophil percentage decreased in group 2 compared to group 1. The infection rate of MP increased significantly in group 2 (34.7%) compared to group 1 (19.3%), while the positive rate of viruses decreased significantly in group 2 (5.3%) compared to group 1 (14.3%). In 2020, the positive rate of MP infection increased significantly in patients with KD compared to the increase in patients with non-KD. The infection rate of MP for younger children aged less than 3 years old was higher in group 2 than in group 1.

CONCLUSION

Compared with the characteristics of KD from 2015 to 2019 years, the incidence of KD was increased in 2020 and was accompanied by a high incidence of MP infection, especially in younger children (less than 3 years old) during the isolation due to COVID-19 pandemic.

Combined IFN-β and PLT Detection Can Identify Kawasaki Disease Efficiently

Objective: To evaluate the value of combined interferon β (IFN-β) and platelet (PLT) detection for Kawasaki disease (KD) identification. Methods: Forty-four children who were newly diagnosed with KD were selected as the KD group. They were divided into acute phase of KD and subacute phase of KD. They were also separated into groups with and without coronary artery disease (CAD) (CAD+ and CAD-, respectively). Meanwhile, 44 children hospitalized with febrile disease and 44 healthy children were selected as a febrile control group and normal control group, whom were attended to at Children's Hospital of Soochow University at the same time. We detected the concentration of IFN-β and PLT of peripheral blood serum for all three groups and analyzed the difference. Results: At acute and subacute phases of KD, both IFN-β and PLT are higher than both the febrile control group and healthy control group, especially at subacute phase; the difference between groups was statistically significant, P < 0.05. Receiver operating characteristic (ROC) curve showed that the areas under the ROC curve (AUCs) of IFN-β and PLT at acute phase of KD were 0.81 and 0.72, respectively; the sensitivity and specificity were 97.22 and 63.64%, and 57.89 and 73.86%, respectively. The AUCs of combined IFN-β and PLT were 0.81 at acute phase and 0.96 at subacute phase of KD, with sensitivity and specificity of 97.22 and 55.26%, and 86.36 and 100%, respectively. The cutoff value of combined IFN-β and PLT detection was IFN-β = 3.51 pg/ml and PLT = 303 × 10⁹/L at acute phase of KD, IFN-β = 4.21 pg/ml and PLT = 368 × 10⁹/L at subacute phase from plot vs. criterion values. However, there are no significant differences between the CAD- group and the CAD+ group for combined IFN-β and PLT, both P > 0.5, neither at acute nor at subacute phase of KD. Conclusion: Combined IFN-β and PLT detection is an efficient biomarker for KD identification. The cutoff values are IFN-β = 3.51 pg/ml and PLT = 303 × 10⁹/L at acute phase of KD and IFN-β = 4.21 pg/ml and PLT = 368 × 10⁹/L at subacute phase.

Kawasaki syndrome: role of superantigens revisited

Kawasaki syndrome (KS) is an acute vasculitis in children complicated by the development of heart disease. Despite its description over 50 years ago, the etiology of coronary artery disease in KS is unknown. High dose intravenous immunoglobulin is the most effective approach to reduce cardiovascular complications. It remains unclear why patients with KS develop coronary artery aneurysms. A subset of patients is resistant to immunoglobulin therapy. Given the heterogeneity of clinical features, variability of history, and therapeutic response, KS may be a cluster of phenotypes triggered by multiple infectious agents and influenced by various environmental, genetic, and immunologic responses. The cause of KS is unknown, and a diagnostic test remains lacking. A better understanding of mechanisms leading to acute KS would contribute to a more precision medicine approach for this complex disease. In the current viewpoint, we make the case for microbial superantigens as important causes of KS.