In serum, only 4 markers (of 27 reliably assayed markers; Supporting Information Table S3; Supporting Information Fig. S2) showed PD‐related changes with P < 0.05 (Fig. 3L–S): VCAM‐1 was increased in patients' serum, and IL‐15 and VEGF‐D were both increased in late versus early PD (Fig. 3L,R–S), whereas VEGF‐C was decreased in all patients (Fig. 3M). Here, VEGFD is linked to Parkinson disease.