Hypoxia-Associated Molecular Subtypes Reveal Immune Checkpoint, Ferroptosis, and m6A Regulatory Heterogeneity in Pediatric Vasculitis.

Vasculitis is a heterogeneous inflammatory vascular disorder with substantial clinical and molecular diversity. However, hypoxia-associated molecular subtypes in pediatric vasculitis and their differences from adult vasculitis remain poorly defined. Transcriptomic data of pediatric and adult vasculitis were obtained from the GEO database. RNA-seq data from GSE129752 were normalized by log2 (TPM+1) transformation. Hypoxia-related genes were used for consensus clustering of pediatric vasculitis samples. Immune checkpoint, ferroptosis-related, and m6A methylation regulator genes were compared between subtypes. Differentially expressed genes between pediatric and adult vasculitis were identified using limma, followed by Gene Ontology enrichment analysis using clusterProfiler. Consensus clustering separated pediatric vasculitis into two hypoxia-associated subtypes, high hypoxia pediatric vasculitis population (high_hypoxia group) and low hypoxia pediatric vasculitis population (low_hypoxia group), with distinct transcriptomic profiles. High_hypoxia group showed higher expression of multiple immune checkpoint genes, including HAVCR2, IGSF8, ITPRIPL1, LAG3, PDCD1, SIGLEC15, and TIGIT. Ferroptosis-related genes EMC2 and ATP5MC3 were also elevated in the high_hypoxia group. In addition, most m6A regulators, including FTO, METTL14, WTAP, and RBM15, were significantly upregulated in the high_hypoxia group. Comparison between pediatric and adult vasculitis identified 85 differentially expressed genes, including 21 upregulated and 64 downregulated genes in pediatric vasculitis. Functional enrichment suggested that pediatric vasculitis was associated with fibroblast proliferation and vascular remodeling, whereas adult vasculitis was enriched in immature T-cell regulation and fatty acid transport. Germline mutation-related genes, including VHL, BRCA1, RET, and MUTYH, showed coordinated correlations with age-related vasculitis. Hypoxia-associated molecular heterogeneity exists in pediatric vasculitis and we observed age-related transcriptomic differences between pediatric and adult disease. These findings provide a foundation for precision classification and future mechanism-based therapeutic strategies.