Calcineurin inhibitor treatment of intravenous immunoglobulin-resistant Kawasaki disease

Adjunctive therapies for Kawasaki disease

Kawasaki disease (KD) is the most common cause of acquired heart disease in children in developed countries.(1,2) The primary goal of treatment is to prevent coronary artery aneurysms (CAA). Between 10 and 20% of KD patients are resistant to treatment with intravenous immunoglobulin (IVIG) and have an almost nine-fold increased risk of developing CAA.(3) In addition, approximately 80-90% of patients who go on to develop CAA have abnormal coronary artery dimensions on their first echocardiogram and can therefore be identified as high-risk patients. These two subsets of KD patients are candidates for adjunctive therapy, in addition to IVIG. Understanding the mechanism of action of IVIG may provide insight into IVIG resistance and guidance for choosing adjunctive therapies in KD. Therapeutic options in the treatment of refractory KD and patients with early CAA include additional IVIG, glucocorticoids, tumor necrosis factor inhibitors, calcineurin inhibitors and interleukin-1 (IL-1) blockers.(3-10) Animal studies suggest that the anti-inflammatory properties of statins may also be beneficial in blocking CAA progression.(6) It is unlikely that these therapies will be studied in large, randomized controlled trials in the future due to required sample size and funding constraints. Thus, data from the research laboratory may be helpful in guiding selection of the most promising adjunctive therapies.

Adjunct cyclosporine therapy for refractory Kawasaki disease in a very young infant

Herein we describe the case of a 6-week-old boy who developed complete Kawasaki disease (KD). The cytokine profile and activation of monocytes and subsequent T cells matched the typical feature of refractory KD. The patient received a total of three courses of i.v. immunoglobulin (IVIG), but did not achieve clinical relief. Adjunctive therapy with oral cyclosporine A (CsA) led to prompt defervescence. This was continued for 7 days without serious adverse events. Coronary artery dilatations regressed within 3 months of follow up. KD infants <3 months of age are at higher risk of coronary artery aneurysm than the older ones. To our knowledge, oral CsA treatment has not been reported in such young infants with KD. The diagnosis and treatment of very young infants with KD are challenging. Adjunctive use of CsA in IVIG treatment could be effective for refractory KD in infants <3 months of age.

The immunomodulatory effects of intravenous immunoglobulin therapy in Kawasaki disease

The introduction of intravenous immunoglobulin (IVIG) for modulation of inflammation in acute Kawasaki disease was a great therapeutic triumph. However, three decades later, the mechanisms underlying immune regulation by IVIG are only beginning to be revealed. Stimulation of an immature myeloid population of dendritic cells that secretes IL-10 and the elucidation of Fc-specific natural regulatory T cells provide insights into the mechanisms of IVIG. Other potential mechanisms include provision of agent-specific neutralizing antibody, anti-idiotype and anti-cytokine antibodies, blockade of activating Fcγ receptors and stimulation of the inhibitory FcγRIIb receptor. New initiatives must seek to understand the mechanisms of IVIG in order to replace it one day with more affordable and more targeted therapies.

Yersinia pseudotuberculosis infection in Kawasaki disease and its clinical characteristics

Background

The etiology of Kawasaki disease (KD) is unknown. Reportedly, there is an association between KD and Yersinia pseudotuberculosis (YPT). Steroid therapy for KD patients with high risk of cardiac sequelae (CS) has been reported; however, the number of reports is limited.

Methods

We conducted a prospective study of 108 patients with newly diagnosed KD in one year to determine how many KD patients have positive anti-YPT antibody titers and/or positive anti-YPT-derived mitogen (YPM) antibody titers. In addition, we tried to identify clinical differences between KD patients in whom YPT infection was or not a contributing factor. We also compared clinical characteristics of patients treated with the protocol of the Randomized controlled trial to Assess Immunoglobulin plus Steroid Efficacy for Kawasaki disease (RAISE) study (RAISE group) and with the conventional Intravenous immunoglobulin (IVIG) protocol (conventional group).

Results

Eleven patients (10 %) were positive for anti-YPT and/or anti-YPM antibodies (positive group) and 97 (90 %) were negative (negative group). Cardiac sequelae (CS) occurred significantly more frequently in the positive than the negative group (two patients, 18 % vs one patient, 1 %, p = 0.027). Forty patients were in the RAISE group. Two of 40 (5 %) in the RAISE group and one of 68 (1.47 %) in the conventional group had CS (p = 0.55).

Conclusions

KD patients with YPT infection had CS significantly more frequently and treatment with RAISE protocol did not decrease the frequency of CS in our cohort, nor did YPT infection affect risk scores of no response to IVIG. However, our sample size was overly small to draw such conclusions. Further investigation in a larger cohort is necessary to confirm our findings. Additionally, further research is needed to determine whether early diagnosis of YPT can prevent KD from developing and reduce the incidence of CS.

Prevalence and predictors of coronary artery disease in adults with Kawasaki disease

BACKGROUND

Accelerated coronary atherosclerosis in patients with Kawasaki disease, in conjunction with coronary artery aneurysm and stenosis that characterise this disease, are potential risk factors for developing coronary artery disease in young adults. We aimed to determine the prevalence and predictors of coronary artery disease in adult patients with Kawasaki disease.

METHODS

All patients aged 18-55 years of age diagnosed with Kawasaki disease were sampled from Nationwide Inpatient Sample database using International Classification of Diseases 9th revision (ICD 9 code 446.1) from 2009 to 2010. Demographics, prevalence of coronary artery disease, and other traditional risk factors in adult patients with Kawasaki disease were analysed using ICD 9 codes.

RESULTS

The prevalence of Kawasaki disease among adults was 0.0005% (n=215) of all in-hospital admissions in United States. The mean age was 27.3 years with women (27.6 years) older than men (27.1 years). Traditional risk factors were hypertension (21%), hyperlipidaemia (15.6%), diabetes (11.5%), tobacco use (8.8%), and obesity (8.8%), with no significant difference between men and women. Coronary artery disease (32.4%), however, was more prevalent in men (44.7%) than in women (12.1%; p=0.03). In multivariate regression analysis, after adjusting for demographics and traditional risk factors, hypertension (OR=13.2, p=0.03) was an independent risk factor of coronary artery disease.

CONCLUSION

There was increased preponderance of coronary artery disease in men with Kawasaki disease. On multivariate analysis, hypertension was found to be the only independent predictor of coronary artery disease in this population after adjusting for other risk factors.

Overview of Pharmacological Treatment Options for Pediatric Patients with Refractory Kawasaki Disease

Kawasaki disease is an autoimmune disease found predominantly in children under the age of 5 years. Its incidence is higher in those who live in Asian countries or are of Asian descent. Kawasaki disease is characterized as an acute inflammation of the vasculature bed affecting mainly the skin, eyes, lymph nodes, and mucosal layers. Although the disease is usually self-limiting, patients may develop cardiac abnormalities that can lead to death. The exact cause of the disease is unknown; however, researchers hypothesize that an infectious agent is responsible for causing Kawasaki disease. Initial treatment options with intravenous immune globulin and aspirin are sufficient to cure most patients who acquire this disease. Unfortunately, in up to one-quarter of patients, the disease will be refractory to initial therapy and will require further management with corticosteroid, immunomodulatory, or cytotoxic agents. The lack of randomized, controlled trials makes treatment of refractory disease difficult to manage. Until larger randomized, controlled trials are published to give more guidance on therapy for this stage of disease, clinicians should use the data available from observational studies and case reports in conjunction with their clinical expertise to make treatment decisions.

The Complexities of the Diagnosis and Management of Kawasaki Disease

Kawasaki disease (KD) must be considered in the differential diagnosis of any child with fever for 4 to 5 days and compatible clinical and laboratory features, and in any infant with prolonged fever and compatible laboratory features, even in the absence of the classic clinical signs. Prompt therapy is required, because delayed or unrecognized KD can lead to lifelong heart disease or death in previously healthy children. Most children with KD respond to a single 2 g/kg dose of intravenous gammaglobulin with oral aspirin, but a small subset require additional therapies to resolve the clinical illness.

Kawasaki disease: insights into pathogenesis and approaches to treatment

This Review summarizes recent advances in understanding of the pathologic processes and pathophysiologic mechanisms leading to coronary arteritis in Kawasaki disease, and describes current approaches to its treatment. Kawasaki disease is the most common cause of acquired heart disease among children in developed countries, in whom the resulting coronary artery abnormalities can cause myocardial ischaemia, infarction and even death. Epidemiologic data strongly suggest an infectious aetiology, although the causative agent has yet to be identified. Genetic factors also increase susceptibility to Kawasaki disease, as indicated by its strikingly high incidence rate in children of Asian ethnicity and by an increased incidence in first-degree family members. The treatment of Kawasaki disease is based on timely administration of intravenous immunoglobulin and aspirin. However, the management of patients who do not respond to this standard therapy remains challenging; although several options are available, comparative data on which to base treatment decisions are scarce. The added value of adjunctive therapy with corticosteroids in patients at particularly high risk of coronary complications has been demonstrated in Japanese populations, but identification of high-risk patients has proven to be difficult in ethnically diverse populations.

Kawasaki disease: pathophysiology, clinical manifestations, and management

Kawasaki Disease, a systemic vasculitis of unknown origin with specific predilection for the coronary arteries, is the most common cause of childhood-acquired heart disease in western countries. Despite its world-wide incidence, the pathophysiology of this enigmatic disease is still under investigation. Diagnosis is made on a clinical basis, with supportive laboratory evidence and imaging. Once identified, timely initiation of treatment is imperative in order to quell the inflammatory response and decrease the incidence of long-term sequelae, specifically coronary artery aneurysms. Finally, longitudinal follow-up should be implemented based on risk stratification and individualized to each patient.

Intravenous immunoglobulin, pharmacogenomics, and Kawasaki disease

Kawasaki disease (KD) is a systemic vasculitis of unknown etiology and it is therefore worth examining the multifactorial interaction of genes and environmental factors. Targeted genetic association and genome-wide association studies have helped to provide a better understanding of KD from infection to the immune-related response. Findings in the past decade have contributed to a major breakthrough in the genetics of KD, with the identification of several genomic regions linked to the pathogenesis of KD, including ITPKC, CD40, BLK, and FCGR2A. This review focuses on the factors associated with the genetic polymorphisms of KD and the pharmacogenomics of the response to treatment in patients with intravenous immunoglobulin resistance.

Update on etio and immunopathogenesis of Kawasaki disease

PURPOSE OF REVIEW

This review first discusses the pathogenesis of Kawasaki disease based on the results of recently performed studies aimed at identifying Kawasaki disease-susceptibility genes and the results of analyses of the immune system. Following that, we discuss the findings generated using a murine Kawasaki disease arteritis model and speculate regarding the mechanism of Kawasaki disease onset based on immune function aberrations seen in that model.

RECENT FINDINGS

Recent advances in gene analysis studies of Kawasaki disease are contributing not only to prediction of disease susceptibility but also to improving our understanding of the pathogenesis of Kawasaki disease and development of new improved therapies. In addition, Th17/Treg imbalance is observed in patients with acute-phase Kawasaki disease. Th17/Treg imbalance may be an important factor causing disturbed immunological function. IL-17 induced by Th17 cells have proinflammatory properties and act on inflammatory cells, thereby inducing expression of cytokines and chemokines and resulting in tissue inflammation.

SUMMARY

Kawasaki disease vasculitis may be triggered by aberrant activation of inflammatory cytokines mediated by IL-17 that is produced by Th17 cells that have been activated by some infectious agent(s).

Mercury promotes catecholamines which potentiate mercurial autoimmunity and vasodilation: implications for inositol 1,4,5-triphosphate 3-kinase C susceptibility in kawasaki syndrome

Previously, we reviewed biological evidence that mercury could induce autoimmunity and coronary arterial wall relaxation as observed in Kawasaki syndrome (KS) through its effects on calcium signaling, and that inositol 1,4,5-triphosphate 3-kinase C (ITPKC) susceptibility in KS would predispose patients to mercury by increasing Ca²⁺ release. Hg²⁺ sensitizes inositol 1,4,5-triphosphate (IP3) receptors at low doses, which release Ca²⁺ from intracellular stores in the sarcoplasmic reticulum, resulting in delayed, repetitive calcium influx. ITPKC prevents IP3 from triggering IP3 receptors to release calcium by converting IP3 to inositol 1,3,4,5-tetrakisphosphate. Defective IP3 phosphorylation resulting from reduced genetic expressions of ITPKC in KS would promote IP3, which increases Ca²⁺ release. Hg²⁺ increases catecholamine levels through the inhibition of S-adenosylmethionine and subsequently catechol-O-methyltransferase (COMT), while a single nucleotide polymorphism of the COMT gene (rs769224) was recently found to be significantly associated with the development of coronary artery lesions in KS. Accumulation of norepinephrine or epinephrine would potentiate Hg²⁺-induced calcium influx by increasing IP3 production and increasing the permeability of cardiac sarcolemma to Ca²⁺. Norepinephrine and epinephrine also promote the secretion of atrial natriuretic peptide, a potent vasodilator that suppresses the release of vasoconstrictors. Elevated catecholamine levels can induce hypertension and tachycardia, while increased arterial pressure and a rapid heart rate would promote arterial vasodilation and subsequent fatal thromboses, particularly in tandem. Genetic risk factors may explain why only a susceptible subset of children develops KS although mercury exposure from methylmercury in fish or thimerosal in pediatric vaccines is nearly ubiquitous. During the infantile acrodynia epidemic, only 1 in 500 children developed acrodynia whereas mercury exposure was very common due to the use of teething powders. This hypothesis mirrors the leading theory for KS in which a widespread infection only induces KS in susceptible children. Acrodynia can mimic the clinical picture of KS, leading to its inclusion in the differential diagnosis for KS. Catecholamine levels are often elevated in acrodynia and may also play a role in KS. We conclude that KS may be the acute febrile form of acrodynia.

The roles of Ca2+/NFAT signaling genes in Kawasaki disease: single- and multiple-risk genetic variants

Ca²⁺/nuclear factor of activated T-cells (Ca²⁺/NFAT) signaling pathway may play a crucial role in Kawasaki disease (KD). We investigated 16 genetic variants, selected by bioinformatics analyses or previous studies, in 7 key genes involved in this pathway in a Chinese population. We observed a significantly or marginally increased KD risk associated with rs2720378 GC + CC genotypes (OR = 1.39, 95% CI = 1.07–1.80, P = 0.014) or rs2069762 AC + CC genotypes (OR = 1.28, 95% CI = 0.98–1.67, P = 0.066), compared with their wild type counterparts. In classification and regression tree analysis, individuals carrying the combined genotypes of rs2720378 GC or CC genotype, rs2069762 CA or CC genotype and rs1561876 AA genotype exhibited the highest KD risk (OR = 2.12, 95% CI = 1.46–3.07, P < 0.001), compared with the lowest risk carriers of rs2720378 GG genotype. Moreover, a significant dose effect was observed among these three variants (P_trend < 0.001). In conclusion, this study implicates that single- and multiple-risk genetic variants in this pathway might contribute to KD susceptibility. Further studies on more comprehensive single nucleotide polymorphisms, different ethnicities and larger sample sizes are warranted, and the exact biological mechanisms need to be further clarified.

Single-nucleotide polymorphism rs7251246 in ITPKC is associated with susceptibility and coronary artery lesions in Kawasaki disease

Kawasaki disease (KD) is a multi-systemic vasculitis that preferentially affects children. A single nucleotide polymorphism (SNP) in inositol 1,4,5-trisphosphate 3-kinase C (ITPKC) has been identified to be an important polymorphism in the risk of KD. This study was conducted to comprehensively investigate the associations between all tagging SNPs of ITPKC in the risk of KD in a Taiwanese population. A total of 950 subjects (381 KD patients and 569 controls) were recruited. Seven tagging SNPs (rs11673492, rs7257602, rs7251246, rs890934, rs10420685, rs2607420, rs2290692) were selected for TaqMan allelic discrimination assay. Clinical data of coronary artery lesions (CAL) and aneurysms were collected for analysis. A significant association was found between rs7251246 in ITPKC and CAL formation. Haplotype analysis for ITPKC polymorphisms also confirmed this association in the patients with CAL and aneurysm formation. This is the first study to identify that SNP rs7251246 in ITPKC is associated with the severity of KD.

Diagnosis and classification of Kawasaki disease

Kawasaki disease is an acute systemic vasculitis of unknown etiology. Diagnosis is based on clinical criteria that include fever, exanthema, conjunctivitis, changes in the extremities, erythema of oral mucosa and lips and cervical lymphadenopathy. However, these criteria have low sensitivity and specificity and therefore, other clinical and laboratory features may be helpful in establishing the diagnosis, especially for cases of atypical or incomplete Kawasaki disease. Prognosis depends on the extent of cardiac involvement; coronary aneurysms develop in 20-25% of untreated patients and these may lead to myocardial infarction and sudden death. Treatment with high-dose intravenous immunoglobulin is effective in reducing the risk of coronary aneurysms in most cases and is the treatment of choice for initial Kawasaki disease.

Management of Kawasaki disease

Kawasaki disease (KD) is an acute self-limiting inflammatory disorder, associated with vasculitis, affecting predominantly medium-sized arteries, particularly the coronary arteries. In developed countries KD is the commonest cause of acquired heart disease in childhood. The aetiology of KD remains unknown, and it is currently believed that one or more as yet unidentified infectious agents induce an intense inflammatory host response in genetically susceptible individuals. Genetic studies have identified several susceptibility genes for KD and its sequelae in different ethnic populations, including FCGR2A, CD40, ITPKC, FAM167A-BLK and CASP3, as well as genes influencing response to intravenous immunoglobulin (IVIG) and aneurysm formation such as FCGR3B, and transforming growth factor (TGF) β pathway genes. IVIG and aspirin are effective therapeutically, but recent clinical trials and meta-analyses have demonstrated that the addition of corticosteroids to IVIG is beneficial for the prevention of coronary artery aneurysms (CAA) in severe cases with highest risk of IVIG resistance. Outside of Japan, however, clinical scores to predict IVIG resistance perform suboptimally. Furthermore, the evidence base does not provide clear guidance on which corticosteroid regimen is most effective. Other therapies, including anti-TNFα, could also have a role for IVIG-resistant KD. Irrespective of these caveats, it is clear that therapy that reduces inflammation in acute KD, improves outcome. This paper summarises recent advances in the understanding of KD pathogenesis and therapeutics, and provides an approach for managing KD patients in the UK in the light of these advances.

Treatment response in Kawasaki disease is associated with sialylation levels of endogenous but not therapeutic intravenous immunoglobulin G

Objectives

Although intravenous immunoglobulin (IVIG) is highly effective in Kawasaki disease (KD), mechanisms are not understood and 10-20% of patients are treatment-resistant, manifesting a higher rate of coronary artery aneurysms. Murine models suggest that α2-6-linked sialic acid (α2-6Sia) content of IVIG is critical for suppressing inflammation. However, pro-inflammatory states also up-regulate endogenous levels of β-galactoside:α2-6 sialyltransferase-I (ST6Gal-I), the enzyme that catalyzes addition of α2-6Sias to N-glycans. We asked whether IVIG failures correlated with levels of α2-6Sia on infused IVIG or on the patient’s own endogenous IgG.

Methods

We quantified levels of α2-6Sia in infused IVIG and endogenous IgG from 10 IVIG-responsive and 10 resistant KD subjects using multiple approaches. Transcript levels of ST6GAL1, in patient whole blood and B cell lines were evaluated by RT-PCR. Plasma soluble (s)ST6Gal-I levels were measured by ELISA.

Results

There was no consistent difference in median sialylation levels of infused IVIG between groups. However, α2-6Sia levels in endogenous IgG, ST6GAL1 transcript levels, and ST6Gal-I protein in serum from IVIG-resistant KD subjects were lower than in responsive subjects at both pre-treatment and one-year time points (p <0.001, respectively).

Conclusions

Our data indicate sialylation levels of therapeutic IVIG are unrelated to treatment response in KD. Rather, lower sialylation of endogenous IgG and lower blood levels of ST6GALI mRNA and ST6Gal-I enzyme predict therapy resistance. These differences were stable over time, suggesting a genetic basis. Because IVIG-resistance increases risk of coronary artery aneurysms, our findings have important implications for the identification and treatment of such individuals.

Kawasaki disease: part I. Diagnosis, clinical features, and pathogenesis

Kawasaki disease, or mucocutaneous lymph node syndrome, most commonly affects children between 6 months and 5 years of age. Approximately 90% of patients have mucocutaneous manifestations. This article will focus on the epidemiology of Kawasaki disease in the United States as it relates to other countries, the diagnosis of Kawasaki disease, its clinical course, and the currently accepted theories of pathogenesis. A particular focus is given to the various dermatologic manifestations that may occur.

Epidemiology of Kawasaki disease: prevalence from national database and future trends projection by system dynamics modeling

OBJECTIVE

To update the epidemiologic trend in Kawasaki disease (KD) and develop models for projection.

STUDY DESIGN

From our national databases 2000-2010 and previous studies, we obtained the epidemiologic data to develop and validate system dynamics models. Population model incorporated birth rate and mortality. KD model incorporated the population at risk, incidence, and risk of coronary complications.

RESULTS

The average annual incidence in age group <5, 5-10, 10-15, and 15-20 years was 67.3, 5.75, 0.79, and 0.26 per 100,000. The KD population was 23,349 and the model estimated 20,254 patients with KD, and 25% of these patients received medical care or continued surveillance in 2010. Projection up to 2030 suggests an average of 725 new patients with KD annually and a KD population of 35,006 by 2030. In 2030, 1469 patients with KD will need medical care for coronary complications. Simulation on the model modified to US data is also effective and suggests an average of 6200 new patients annually and KD population of 161,776 by 2030, and 5664 patients will need coronary care in 2030. By 2030, there will be 1 per 700 people in Taiwan and 1 per 1600 in the US with a history of KD.

CONCLUSION

Simulations on our system dynamics models tailored to any epidemiologic and outcome variables and any changes with medical advance can dynamically project the futures.

Management of acute and refractory Kawasaki disease

Acute Kawasaki disease (KD) is treated with high-dose intravenous immunoglobulin (IVIG), which is proven to decrease the incidence of coronary artery aneurysms from 25% to less than 5%. Aspirin is also given, although the evidence base is less secure. There is increasing evidence for steroid therapy as adjunctive primary therapy with IVIG, especially in Asian children. Approximately 10-30% of patients fail to respond to the initial IVIG and are at increased risk of coronary artery aneurysms. The optimal treatment for IVIG-nonresponsive KD remains controversial. Management options include further dose(s) of IVIG, corticosteroids, TNF-α blockade, cyclosporin A, anti-IL-1 and anti-CD20 therapy. In this article, the authors review the current evidence for treatment of acute KD and discuss options for IVIG nonresponders.

Understanding the pathogenesis of Kawasaki disease by network and pathway analysis

Kawasaki disease (KD) is a complex disease, leading to the damage of multisystems. The pathogen that triggers this sophisticated disease is still unknown since it was first reported in 1967. To increase our knowledge on the effects of genes in KD, we extracted statistically significant genes so far associated with this mysterious illness from candidate gene studies and genome-wide association studies. These genes contributed to susceptibility to KD, coronary artery lesions, resistance to initial IVIG treatment, incomplete KD, and so on. Gene ontology category and pathways were analyzed for relationships among these statistically significant genes. These genes were represented in a variety of functional categories, including immune response, inflammatory response, and cellular calcium ion homeostasis. They were mainly enriched in the pathway of immune response. We further highlighted the compelling immune pathway of NF-AT signal and leukocyte interactions combined with another transcription factor NF- κ B in the pathogenesis of KD. STRING analysis, a network analysis focusing on protein interactions, validated close contact between these genes and implied the importance of this pathway. This data will contribute to understanding pathogenesis of KD.

Advances in the treatment of Kawasaki disease

PURPOSE OF REVIEW

Intravenous immunoglobulin (IVIG) and aspirin is the standard initial therapy in the treatment of Kawasaki disease. Some patients have persistent or recrudescent fever despite this therapy. Although there is no conclusive body of evidence defining the best second and third-line therapies for Kawasaki patients, there have been several recent studies published describing the results of these therapies.

RECENT FINDINGS

This review summarizes the current recommendations for the initial therapy and describes the second and third-line therapies studied in Japan and the United States. A recent study in a Japanese population of Kawasaki disease patients at high risk for IVIG resistance found that the group receiving steroids, in addition to IVIG and aspirin, had fewer coronary artery abnormalities than the group receiving IVIG and aspirin alone. Small studies of etanercept and infliximab have showed these TNF-alpha blockers to be well tolerated and effective in the resolution of fever.

SUMMARY

Although most practitioners in the USA use IVIG as a second-line therapy for those Kawasaki disease patients who have persistent or recrudescent fever, promising new therapies are under study. Infliximab and steroids are currently the two agents that have been most studied. However, larger studies and studies in genetically diverse populations are needed.