Five proteins were found to be present within endometriosis samples (stage I/II and stage III/IV) that were absent from the control samples: (fragments of) peroxiredoxin-1 (PRDX1), histone H2A type 2-C, annexin A2 (ANXA2), inter-α-trypsin inhibitor heavy chain H4 (ITIH4) (fragment), and tubulin α-chain. The gene discussed is PRDX1; the disease is endometriosis.