By using 2D-PAGE MALDI-TOF and peptide sequence by tandem MS/MS, Starita-Geribaldi et al. [116] identified several proteins that were undetectable or present at low levels in the SP of azoospermic patients: CRISP1, CLU, NPC2, superoxide-dismutase (SOD) and serum amyloid p-component (SAP), the last one being undetectable in azoospermic patients with Sertoli cell-only syndrome. Here, APCS is linked to Sertoli Cell-Only Syndrome.