Editors: Donna E. Hansel, MD, PhD, division head of pathology and laboratory medicine, MD Anderson Cancer Center, Houston; James Solomon, MD, PhD, assistant professor, Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York; Erica Reinig, MD, assistant professor and medical director of molecular diagnostics, University of Wisconsin-Madison; Marcela Riveros Angel, MD, molecular genetic pathology fellow, Department of Pathology, Oregon Health and Science University, Portland; Maedeh Mohebnasab, MD, assistant professor of pathology, University of Pittsburgh; Alicia Dillard, MD, molecular pathologist, Sonic Healthcare USA, Rye Brook, NY; and Richard Wong, MD, PhD, assistant professor of pathology, University of California San Diego.
Use of cell-free RNA profiling for molecular characterization of Kawasaki disease subgroups
August 2026—Kawasaki disease is an acute vasculitis of childhood and the most common cause of acquired heart disease in children worldwide. Up to 25 percent of untreated patients develop coronary artery aneurysms. The variable clinical presentation of Kawasaki disease (KD) complicates diagnosis, treatment, and understanding of the disease and highlights the need for molecular tools to stratify patients into biologically meaningful subgroups. A previous data-driven cluster analysis identified four clinically distinct KD subgroups based on 14 clinical and laboratory variables, including hepatic enzyme elevation, immune cell counts, coronary artery aneurysm rates, and response to intravenous immunoglobulin, but the molecular basis for these subgroups remains unknown. Therefore, the authors conducted a study to explore the potential of cell-free RNA (cfRNA) for molecularly characterizing these disease subtypes. The study used plasma samples collected before treatment from 98 KD patients previously categorized into the four clinical subgroups. The authors further analyzed 86 samples from febrile pediatric controls and five samples from healthy children. CfRNA was interrogated at three levels of analysis: differential transcript abundance, pathway enrichment, and cell type of origin. The authors also performed unsupervised hierarchical clustering of the cfRNA samples to explore de novo molecular subtyping of KD. Analysis showed significant differences in molecular signatures between the four KD subgroups. Each had distinct patterns of RNA expression, biological pathway activity, and cellular origins of circulating RNA. Subgroup one had strong evidence of liver involvement, with markers of liver cell injury and dysfunction. Subgroup two was characterized by signatures related to mitochondrial stress, immune activation, and cell death-related pathways, suggesting an alternative inflammatory mechanism. Subgroup three was defined by increased platelet activation and dendritic cell activity-related features, suggesting increased immune surveillance and antigen processing. Subgroup four, which was composed of younger children, showed unique developmental signatures and evidence of kidney and heart involvement, including elevated markers from cardiac muscle cells. The authors also examined the tissues contributing to circulating RNA and found subgroup-specific patterns of cellular injury. For instance, subgroup one was enriched in liver-derived RNA, and subgroup three was enriched in platelet-derived cfRNA, thereby establishing connections between clinical features and biological processes. Furthermore, the molecular data were used to identify some of the clinical subgroups without prior assumptions, providing additional evidence that these subgroups represent biologically distinct entities of KD rather than different manifestations of a single disease process. The authors concluded that cfRNA profiling can identify meaningful molecular differences among patients with KD and that the disease is a collection of multiple biologically distinct subtypes. The study results highlight the potential of cfRNA-based biomarkers to improve patient stratification, personalize treatment, and provide a better understanding of disease mechanisms in pediatric vasculitis.
Loy CJ, Wang H, Kim J, et al. Molecular characterization of Kawasaki disease subgroups using cell-free RNA profiling. Sci Rep. 2025. doi.org/10.1038/s41598-025-15843-7
Correspondence: Dr. Jane C. Burns at jcburns@health.ucsd.edu or Dr. Iwijn De Vlaminck at vlaminck@cornell.edu
Cancer predisposition associated with pathogenic germline variants in children referred for genetic testing
Next-generation sequencing has revolutionized the diagnosis of pediatric genetic disorders, but the cancer risk of germline pathogenic variants found in children referred for nononcologic indications is poorly defined. Longitudinal data on the relationship between germline variant status and timed tumor outcomes in this population do not exist, which limits the clinical utility of secondary findings and guidance for genetic counselors and families. The authors conducted a large-scale study to profile the underlying cancer risk and tumor characteristics of children who have pathogenic germline variants and, thereby, provide information to support genetic counseling and early prevention measures. They analyzed exome sequencing data from 75,602 pediatric patients referred for genetic testing between 2016 and 2025. Most of the children were assessed for neurological symptoms, metabolic disorders, immune system abnormalities, or other suspected genetic conditions. The authors examined 139 cancer-susceptibility genes for pathogenic or likely pathogenic genetic variants and analyzed their association with development of cancer over time. They found more than 500 pathogenic or likely pathogenic variants. The authors also identified nearly 3,900 variants of uncertain significance leaning toward pathogenicity (VUS-LP) using their in-house Clever (Clinical Evidence-based Variant Interpreter) annotation and evaluation system, developed in accordance with American College of Medical Genetics and Genomics guidelines. These variants exhibited evidence suggestive of disease causation but did not meet the threshold for classification as likely pathogenic. Approximately one-third of 411 children who developed tumors before or during the study period had a clearly pathogenic inherited mutation. The most frequently altered genes were NF1, TSC2, RB1, and WT1, which are well-known cancer-predisposition genes. The mutations were associated with a wide range of tumor types, emphasizing the diverse ways in which inherited genetic alterations can affect susceptibility to cancer in childhood. A particularly important finding came from follow-up data on 64,187 of the children who had no signs of cancer at the time they underwent genetic testing. The children with pathogenic germline variants in cancer-predisposing genes had more than a 10-fold increased risk for cancer compared with other groups, indicating that inherited variants may be good predictors of future cancer risk. The study also demonstrated that many high-risk children would not have been identified through traditional cancer screening because they were initially referred for unrelated medical issues. This suggests that genomic testing may provide useful secondary findings and help clinicians identify children who may benefit from closer monitoring and preventive care. The authors concluded that pathogenic germline variants are rare but clinically relevant in pediatric patients undergoing genetic testing. Identifying these variants can lead to earlier cancer surveillance, more personalized medical management, and genetic counseling for families. Therefore, this study highlights the need to incorporate cancer-risk assessment into wider genetic testing programs to improve long-term outcomes for children at higher risk of developing cancer.
Wang H, Dong X, Xiao F, et al. Pathogenic germline variations and cancer risks in pediatric patients referred for genetic testing. Nat Med. 2026. doi.org/10.1038/s41591-026-04423-5
Correspondence: Dr. Fei Liu at liufei_2359@163.com or Dr. Hao Li at lihao7272@163.com