Britta Maurer

Objectives We investigated the potential of serum proteins for distinguishing clinical and molecular subtypes in patients with GCA. Methods Proximity extension assays were used to analyse 1463 proteins in serum samples from patients with new-onset GCA (n = 16) and patients who have achieved remission (n = 13). Unsupervised and supervised cluster analyses were performed. Results Unsupervised cluster analysis identified three distinct clusters based on the protein signature. Compared with cluster 2, patients of cluster 1 had fewer PMR symptoms, increased levels of macrophage migration inhibitory factor (MIF) and pronounced NF-κB, STAT5 and IL-1 signalling. The changes in serum proteins upon remission differed between cluster 1 and 2. Patients with cranial GCA were characterized by altered endothelial and Th17 signalling, whereas patients not responding to treatment within the GUSTO-trial showed increased Th1 and diminished B cell signalling. Patients with anterior ischaemic optic neuropathy displayed higher levels of CHI3L1 (YKL40) and MMP12, and reduced levels of TIMP3. Conclusion Protein profiling identified patient clusters in GCA with distinct proteomic features and therefore likely different pathophysiology. These unique proteomic footprints might lead to more targeted treatments in future.