Objectives <p>Peripheral helper T (Tph) cells, a recently identified Th cell subset, have been implicated in various autoimmune diseases. However, their role in granulomatosis with polyangiitis (GPA) remains unclear. This study aimed to investigate the potential clinical significance of circulating Tph cells (cTph) in GPA.</p> Methods <p>Peripheral blood mononuclear cells were collected from 74 remission GPA-patients, 26 active GPA-patients and 22 age- and sex-matched healthy controls. Flow cytometry was used to quantify cTph cells and their subset distribution. Single-cell multi-omics profiling was performed in an independent cohort (5 remission GPA-patients, 5 active GPA-patients and 5 healthy controls). Plasma IL-21 levels were measured by enzyme-linked immunosorbent assay, and associations between cTph cells and clinical parameters were evaluated.</p> Results <p>active GPA-patients showed an increased frequency and absolute number of cTph compared to remission GPA-patients, and both GPA groups exhibited cTph2-skewed distribution compared to healthy controls. Remission GPA-patients with generalized disease exhibited higher cTph frequencies than those with localized disease. cTph cells from active GPA-patients displayed an activated phenotype and a transcriptional profile marked by pro-inflammatory and survival-associated genes. Plasma IL-21 levels did not differ significantly between the three groups. Notably, absolute counts of memory cTph and cTph2 cells correlated positively with clinical markers of disease activity, and were significantly elevated in GPA patients with higher cytoplasmic antineutrophil cytoplasmic antibody (c-ANCA) titers.</p> Conclusions <p>cTph cells are expanded and exhibit an activated, pro-inflammatory profile with a cTph2-skewed distribution in active GPA-patients. Their association with disease activity may support a potential role in disease pathogenesis and highlight their potential as therapeutic targets, warranting further investigation.</p>